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Ampicillin

Ampicillin is a penicillin antibiotic used to treat a wide range of bacterial infections, including respiratory tract infections, urinary tract infections, meningitis, gastrointestinal infections, and serious bloodstream infections.

Brand names AmcillOmnipenPenbritinPfizerpenPolycillin +3 more
Drug class Penicillin-class Antibacterial
Rx Forms 2
Dr. Brian Staiger, PharmD, BCPS
Reviewed by Last reviewed Jul 10, 2026 Content updated Oct 2, 2026
🧬 Where this information comes from Click to expand

The clinical label records used on this page are FDA-filed Structured Product Labeling (SPL) retrieved through openFDA. We identified 40 clinical label sets within the page’s selected clinical scope after exact ingredient or ingredient-combination matching and applicable route/form matching. Forms, routes, brands, labelers, strengths, and NDC product-record counts are built separately from matching FDA National Drug Code Directory records. The linked DailyMed document is a representative official source for verification, not the page’s only clinical source. View the linked label on DailyMed →

How we combine label and product data →
Other forms & routes:
Injection
Ampicillin at a glance The quick version — the full detail is in the Patient Information Guide below.
Dr. Brian Staiger, PharmD, BCPS
The Pharmacist’s Take By · Clinical pharmacist · Written

Ampicillin is a penicillin antibiotic that kills bacteria by blocking them from building cell walls, used for urinary, respiratory and serious infections such as meningitis and bloodstream infections. An older standby on the U.S. market since about 1971 and available generically, it is now given mostly by injection in hospitals, since its cousin amoxicillin has largely taken over by mouth. Most people tolerate it well, and the usual complaints are diarrhea, nausea or a mild, blotchy, itchy rash. Watch for a true allergic reaction (hives, throat swelling, trouble breathing), which needs emergency care, or a rash that spreads, blisters or peels, and make sure any past penicillin or cephalosporin allergy is known before the first dose.

Clinical pearls

  • Finish the whole course even if you feel better, and space doses evenly through the day and night.
  • Ampicillin may make birth control pills less effective and cause breakthrough bleeding, so use a backup method like condoms during the course.
  • Allopurinol, a gout medicine, taken together with ampicillin greatly raises the chance of a skin rash.
  • New or watery diarrhea, even weeks after the last dose, can signal C. diff, a serious bowel infection worth calling about promptly.
How we write & review this content — our editorial policy →
How you get itPrescription only
Comes asInjection, Capsule
Earliest FDA record1965
Companies listing it with the FDA32
FDA label last updatedMay 23, 2023
FDA’s strongest warning (boxed)None on the label

Patient information guide — a plain-language walkthrough of Ampicillin, written from its FDA label.

What Ampicillin is used for

▾

Ampicillin is a penicillin antibiotic used to treat bacterial infections caused by susceptible organisms across a range of body systems.

  • Respiratory tract infections — caused by bacteria such as Streptococcus pneumoniae, Staphylococcus aureus, H. influenzae, and Group A streptococci
  • Bacterial meningitis (infection of the lining around the brain and spinal cord) — Ampicillin injection is used for meningitis caused by E. coli, Group B Streptococci, Listeria monocytogenes, and N. meningitidis; Ampicillin capsules are indicated for meningitis caused by N. meningitidis
  • Septicemia and endocarditis (serious bloodstream and heart infections) — Ampicillin injection is used for these life-threatening conditions caused by susceptible Gram-positive and Gram-negative organisms
  • Urinary tract infections — caused by susceptible E. coli and Proteus mirabilis
  • Genitourinary tract infections, including gonorrhea — Ampicillin capsules are specifically indicated for these infections
  • Gastrointestinal infections — including typhoid fever (Salmonella typhi), other Salmonella infections, and dysentery (Shigella); both oral and intravenous forms may be used
  • Ampicillin injection (intramuscular or intravenous) is reserved for moderate to severe infections or when patients cannot take oral medication; a switch to oral Ampicillin capsules is made as soon as clinically appropriate

How Ampicillin works

▾

Ampicillin kills bacteria by blocking the construction of their cell walls. Bacteria need a strong cell wall to hold their shape and survive. By interfering with the enzymes that build this wall, ampicillin causes the bacterial cell to fall apart and die. This effect is most powerful while bacteria are actively growing and multiplying.

Ampicillin does not destroy penicillinase — an enzyme some bacteria produce to break down penicillin-type antibiotics. This means bacteria that make penicillinase are resistant to ampicillin and it will not work against them. Your doctor will use lab testing to confirm the bacteria causing your infection are susceptible before or during treatment.

Ampicillin dosage

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Ampicillin is available as an oral capsule and as an injectable form given into a vein or muscle by a healthcare provider. The injectable forms are typically used for more serious infections or when oral medication is not an option. Doses are generally given every 6 to 8 hours, with the exact schedule depending on the type and severity of infection and the patient's weight.

  • Take or receive every dose as scheduled — do not skip doses.
  • Complete the full prescribed course even if you feel better early.
  • If you miss a dose, take it as soon as you remember; if it's almost time for the next dose, skip the missed one — never double up.
  • Follow your prescriber's instructions on food timing; ask your pharmacist if you are unsure.

Dosing details from the FDA-approved label

From the Ampicillin prescribing information (“Dosage and Administration”). Doses are set by your prescriber for your product, condition, kidney function and age — never change a dose on your own.

  • Infections of the respiratory tract and soft tissues - patients weighing 40 kg (88 lbs) or more
    • 250 mg to 500 mg every 6 hours
    • Weight 40 kg (88 lbs) or more
  • Infections of the respiratory tract and soft tissues - patients weighing less than 40 kg (88 lbs)
    • 25 to 50 mg/kg/day in equally divided doses at 6- to 8-hour intervals
    • Weight less than 40 kg (88 lbs)
  • Infections of the gastrointestinal and genitourinary tracts (including those caused by Neisseria gonorrhoeae in females) - patients weighing 40 kg (88 lbs) or more
    • 500 mg every 6 hours
    • Weight 40 kg (88 lbs) or more
  • Infections of the gastrointestinal and genitourinary tracts (including those caused by Neisseria gonorrhoeae in females) - patients weighing less than 40 kg (88 lbs)
    • 50 mg/kg/day in equally divided doses at 6- to 8-hour intervals
    • Weight less than 40 kg (88 lbs)
  • Urethritis in males due to N. gonorrhoeae (adults)
    • Two doses of 500 mg each at an interval of 8 to 12 hours
    • Treatment may be repeated if necessary or extended if required
  • Bacterial meningitis - adults and children
    • 150 to 200 mg/kg/day in equally divided doses every 3 to 4 hours
    • Treatment may be initiated with intravenous drip therapy and continued with intramuscular injections
  • Septicemia - adults and children
    • 150 to 200 mg/kg/day
    • Start with intravenous administration for at least three days and continue with the intramuscular route every 3 to 4 hours
  • Neonates (28 days or less postnatal age) with bacterial meningitis and septicemia - gestational age 34 weeks or less, postnatal age 7 days or less
    • 100 mg/kg/day in equally divided doses every 12 hours
    • Based on gestational and postnatal age (Table 3)
  • Neonates with bacterial meningitis and septicemia - gestational age 34 weeks or less, postnatal age 8 days or more and less than 28
    • 150 mg/kg/day in equally divided doses every 12 hours
    • Based on gestational and postnatal age (Table 3)
  • Neonates with bacterial meningitis and septicemia - gestational age greater than 34 weeks, postnatal age 28 days or less
    • 150 mg/kg/day in equally divided doses every 8 hours
    • Based on gestational and postnatal age (Table 3)
Read the label’s full dosing text

DOSAGE AND ADMINISTRATION Infections of the respiratory tract and soft tissues. Patients weighing 40 kg (88 lbs) or more: 250 mg to 500 mg every 6 hours. Patients weighing less than 40 kg (88 lbs): 25 to 50 mg/kg/day in equally divided doses at 6- to 8-hour intervals. Infections of the gastrointestinal and genitourinary tracts (including those caused by Neisseria gonorrhoeae in females). Patients weighing 40 kg (88 lbs) or more: 500 mg every 6 hours. Patients weighing less than 40 kg (88 lbs): 50 mg/kg/day in equally divided doses at 6- to 8-hour intervals. In the treatment of chronic urinary tract and intestinal infections, frequent bacteriological and clinical appraisal is necessary. Smaller doses than those recommended above should not be used. Higher doses should be used for stubborn or severe infections. In stubborn infections, therapy may be required for several weeks. It may be necessary to continue clinical and/or bacteriological follow-up for several months after cessation of therapy. Urethritis in males due to N. gonorrhoeae : Adults: Two doses of 500 mg each at an interval of 8 to 12 hours. Treatment may be repeated if necessary or extended if required. In the treatment of complications of gonorrheal urethritis, such as prostatitis and epididymitis, prolonged and intensive therapy is recommended. Cases of gonorrhea with a suspected primary lesion of syphilis should have darkfield examinations before receiving treatment. In all other cases where concomitant syphilis is suspected, monthly serological tests should be made for a minimum of four months. The doses for the preceding infections may be given by either the intramuscular or intravenous route. A change to oral ampicillin may be made when appropriate. Bacterial Meningitis. Adults and children: 150 to 200 mg/kg/day in equally divided doses every 3 to 4 hours. (Treatment may be initiated with intravenous drip therapy and continued with intramuscular injections.) The doses for other infections may be given by either the intravenous or intramuscular route. Neonates (less than or equal to 28 days of postnatal age): Dosage should be based on Gestational age and Postnatal age according to Table 1.

Excerpted — the section continues on the label. Read the full Dosage and Administration section on DailyMed →

Ampicillin side effects

▾

Common side effects

  • Diarrhea
  • Nausea or vomiting
  • Skin rash (mild, mildly itchy, blotchy rash)
  • Sore mouth or tongue
  • Glossitis (inflammation of the tongue)
  • Stomatitis (mouth sores)
  • Elevated liver enzymes (detected on blood tests)

When to get medical help

  • Seek emergency help immediately if you develop signs of a severe allergic reaction: hives, swelling of the face or throat, difficulty breathing, or sudden drop in blood pressure (anaphylaxis).
  • Call your doctor right away if you develop a severe or spreading skin rash, blistering, or skin peeling — these can be signs of serious skin reactions like Stevens-Johnson syndrome or toxic epidermal necrolysis.
  • Contact your doctor if you develop new or worsening diarrhea during or after treatment — this could signal a serious bowel infection caused by Clostridioides difficile (C. diff).
  • Tell your doctor about any signs of liver problems: yellowing of the skin or eyes (jaundice), dark urine, or severe stomach pain.
  • Report any unusual bruising or bleeding, which may indicate blood count changes.

Most side effects from ampicillin are related to sensitivity reactions and are more common in people with a history of allergies or prior penicillin reactions.

  • Diarrhea, nausea, or vomiting — especially with oral forms
  • Mild, blotchy, itchy skin rash — fairly common and often appears after the first week of treatment
  • Sore mouth or tongue, mouth sores
  • Glossitis (tongue inflammation) or stomatitis (mouth sores)
  • Hives or itching
  • Elevated liver enzymes seen on blood tests
  • Rarely: changes in blood cell counts (anemia, low platelets, low white blood cells)

If you develop a rash that is spreading, blistering, or peeling; severe diarrhea; signs of an allergic reaction (swelling, difficulty breathing); or yellowing of the skin or eyes — stop the medication and seek medical attention right away.

Ampicillin warnings and precautions

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  • Severe allergic reactions (anaphylaxis): Ampicillin can cause life-threatening allergic reactions. Risk is higher with injections and in people with known penicillin or cephalosporin allergies, or multiple drug allergies. Emergency treatment with epinephrine is required if anaphylaxis occurs.
  • Serious skin reactions: Rare but dangerous skin conditions — including Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), DRESS (drug reaction with widespread organ involvement), and others — have been reported. Stop ampicillin immediately if a rash appears and begins to worsen or blister.
  • C. difficile-associated diarrhea (CDAD): Like all antibiotics, ampicillin can disrupt normal gut bacteria and allow C. difficile (C. diff) to overgrow, causing severe diarrhea or colitis (bowel inflammation). This can occur even weeks after finishing the course.
  • Liver toxicity (hepatotoxicity): Hepatitis and cholestatic jaundice (a liver/bile problem) have been reported, rarely resulting in death. Patients with liver disease should have liver function monitored regularly during treatment.

Ampicillin interactions

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Tell your doctor and pharmacist about all medications you take before starting ampicillin, especially:

  • Allopurinol (used for gout) — greatly increases the chance of developing a skin rash when taken with ampicillin.
  • Bacteriostatic antibiotics (chloramphenicol, erythromycins, sulfonamides, tetracyclines) — these may reduce ampicillin's ability to kill bacteria by slowing bacterial growth, which ampicillin needs to act effectively.
  • Oral contraceptives (birth control pills) — ampicillin may make them less effective; breakthrough bleeding may occur, and a backup method of contraception is advisable during treatment.
  • Probenecid (used for gout or to treat certain infections) — reduces the kidney's ability to clear ampicillin, raising ampicillin blood levels and increasing the risk of side effects.

Interactions listed in the FDA-approved label

From the Ampicillin prescribing information (“Drug Interactions”): what the manufacturer studied or reported to the FDA.

  • Allopurinol: Substantially increased incidence of skin rashes in patients receiving both drugs compared to ampicillin alone; it is not known whether this is due to allopurinol or the hyperuricemia present in these patients.
  • Bacteriostatic antibiotics (chloramphenicol, erythromycins, sulfonamides, tetracyclines): May interfere with the bactericidal effect of penicillins; demonstrated in vitro, clinical significance not well-documented.
  • Oral contraceptives: May be less effective and increased breakthrough bleeding may occur.
  • Probenecid: May decrease renal tubular secretion of ampicillin resulting in increased blood levels and/or ampicillin toxicity.
Read the label’s full interactions text

Drug Interactions The concurrent administration of allopurinol and ampicillin increases substantially the incidence of skin rashes in patients receiving both drugs as compared to patients receiving ampicillin alone. It is not known whether this potentiation of ampicillin rashes is due to allopurinol or the hyperuricemia present in these patients.

Read the full Drug Interactions section on DailyMed →

Not a complete list. The label covers the interactions the manufacturer studied or reported, and our own interaction database does not cover every medicine either. Bring your full medication list, including vitamins and herbal products, to your pharmacist.

🌿50 supplements and herbs with documented Ampicillin interactions, ranked by severity Check Ampicillin against a supplement or herb →

Before taking Ampicillin

▾
  • Tell your doctor if you have ever had a serious allergic reaction — especially anaphylaxis or a severe skin reaction — to any penicillin or cephalosporin antibiotic.
  • Do not take ampicillin if you previously developed cholestatic jaundice (a liver/bile condition) while taking ampicillin.
  • Do not use ampicillin for infections caused by penicillinase-producing bacteria — it will not be effective.
  • Tell your doctor if you have liver disease — liver function should be checked regularly during treatment.
  • Tell your doctor if you have kidney problems — ampicillin is cleared through the kidneys, and reduced kidney function can cause the drug to build up.
  • Tell your doctor about all allergies (including to foods, latex, or other drugs) and if you have a history of asthma, hay fever, or hives — these increase the risk of an allergic reaction.
  • Tell your doctor about all other medications, supplements, and herbal products you take, particularly allopurinol, probenecid, or oral contraceptives.

Ampicillin overdose

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If too much ampicillin is taken, stop the medication and contact a healthcare provider or poison control center right away. Treatment is supportive — meaning doctors will manage symptoms as they arise. In patients with kidney problems, ampicillin can be removed from the body using hemodialysis (a kidney-filtering treatment) if needed, but not by peritoneal dialysis.

What Ampicillin does in the body

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Ampicillin kills susceptible bacteria by blocking the final step in building their cell walls, causing the cells to rupture and die. This action is most effective against bacteria that are actively multiplying. Ampicillin does not destroy penicillinase, so bacteria that produce this enzyme can break down the drug and resist its effects. Laboratory susceptibility testing is used to confirm that the bacteria causing an infection will respond to ampicillin before or during treatment.

How your body processes Ampicillin

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Ampicillin spreads readily into most body tissues and fluids after administration. It does not penetrate the brain or cerebrospinal fluid well unless the meninges (the protective membranes around the brain) are inflamed. Ampicillin is primarily excreted unchanged through the kidneys into the urine; taking probenecid alongside it slows this process and raises blood levels of the drug. It is the least protein-bound of the penicillins — meaning more of the drug is active and free in the bloodstream compared to other penicillins. The drug also appears in bile at higher concentrations than in blood.

How to store Ampicillin

▾

Store at 20° to 25°C (68° to 77°F) .

Written from the FDA-approved label with AI and reviewed by our pharmacy team. How we use AI →

50

Supplements & herbs that interact with Ampicillin

50 supplements and herbal products have documented interactions with Ampicillin in the licensed clinical database we use. Most are manageable — but your pharmacist should know about everything you take, including vitamins and herbals.

Severity mix
  • Major · 1
  • Moderate · 39
  • Minor · 10
ACTIVATED CHARCOAL Major BACILLUS COAGULANS Moderate Bacillus Subtilis Moderate BIFIDOBACTERIUM ANIMALIS SUBSP. LACTIS Moderate BIFIDOBACTERIUM BIFIDUM Moderate BIFIDOBACTERIUM BREVE Moderate BIFIDOBACTERIUM LONGUM Moderate BIOFEEDBACK Moderate +42 more
Every supplement checked against Ampicillin — ranked by severity The full interaction hub: 1 major · 39 moderate · 10 minor · every one linked to its full report. Check Ampicillin against your exact supplements

Educational information from a licensed clinical database (Natural Medicines) — see our data sources & update cadence. Not medical advice: an interaction being documented does not mean it will happen to you; do not start or stop medications or supplements without professional guidance.

7

Nutrient depletion considerations

Ampicillin has been associated with lower levels of 7 nutrients in the clinical literature. This does not mean a deficiency will occur — it means these may be worth discussing with your pharmacist or healthcare provider, especially with long-term use.

Evidence & significance mix
  • Higher significance · 6
  • Moderate · 1
BIOTIN Insignificant Depletion FOLIC ACID Insignificant Depletion RIBOFLAVIN Insignificant Depletion THIAMINE Insignificant Depletion VITAMIN B12 Insignificant Depletion VITAMIN B6 Insignificant Depletion VITAMIN K Moderate Depletion
See the full Ampicillin nutrient depletion report

Educational information from a licensed clinical database (Natural Medicines) — not medical advice. Do not start or stop medications or supplements without professional guidance.

Ampicillin: pharmacist answers to common questions

Quick, plain-English answers to the questions patients ask most about Ampicillin — the kind of thing our pharmacy team would talk through with you at the counter.

What kinds of infections does ampicillin treat?

▾
Ampicillin treats a wide range of bacterial infections — things like respiratory infections, urinary tract infections, certain gastrointestinal infections (including typhoid fever), bacterial meningitis, and serious bloodstream or heart infections. The capsule form is also used for some genitourinary infections, including gonorrhea. Your doctor will confirm that the bacteria causing your infection are actually susceptible to ampicillin before or during treatment.

I've heard ampicillin can cause a rash — should I be worried?

▾
A mild, blotchy, slightly itchy skin rash is fairly common with ampicillin and doesn't always mean you're allergic. It often shows up after the first week of treatment and usually goes away on its own in a few days. However, if the rash is spreading fast, blistering, peeling, or comes with fever or mouth sores, stop the medication right away and call your doctor — those can be signs of a serious reaction that needs immediate attention.

Is it safe to take ampicillin if I'm allergic to penicillin?

▾
Ampicillin is a penicillin antibiotic, so if you've had a serious allergic reaction — especially anaphylaxis or a severe skin reaction — to penicillin or a similar antibiotic called a cephalosporin, you should not take ampicillin. Make sure your doctor knows your complete allergy history before you start. Even a history of multiple drug allergies or allergies to things like hay fever or hives can increase your risk of a reaction.

Can ampicillin affect my birth control pills?

▾
Yes — ampicillin may make oral contraceptives (birth control pills) less effective, and you might have breakthrough bleeding. While you're taking ampicillin, it's a good idea to use a backup method of contraception, like condoms. Talk to your doctor or pharmacist about the best approach for your situation.

I've been having diarrhea since starting ampicillin — is that normal?

▾
Mild diarrhea can happen with ampicillin, especially with the oral capsule form. But if the diarrhea is severe, watery, bloody, or doesn't go away — or even if it starts weeks after you finish the course — call your doctor. This could be a sign of a serious bowel infection called C. difficile (C. diff) that needs its own treatment. Don't take anti-diarrhea medicines without checking with your doctor first in that case.

Do I really need to finish the whole course even if I feel better?

▾
Yes — absolutely finish the full prescribed course. When you start feeling better, it means the antibiotic is working, but there may still be bacteria left that haven't been fully eliminated. Stopping early can allow those remaining bacteria to survive and potentially become harder to treat. It also contributes to antibiotic resistance, which is a broader public health concern.

Is Ampicillin available over the counter?

▾
No. Ampicillin is a prescription medicine: every Ampicillin product listed with the FDA is prescription only, so it is not sold over the counter. Your prescriber decides whether it is appropriate for you, and your pharmacist dispenses it.

When was Ampicillin first available?

▾
The earliest FDA record we hold for Ampicillin is from 1965: its first approval in Drugs@FDA or its earliest product listing in the NDC Directory, whichever is older. Many older medicines were in use before their first formal FDA approval, so this is the earliest date on record, not necessarily when Ampicillin was first used.

Who makes Ampicillin?

▾
32 companies list Ampicillin products in the FDA's NDC Directory, including Sandoz Inc, Medical Purchasing Solutions, LLC, WG Critical Care, LLC. That count includes repackagers and distributors as well as manufacturers, so fewer companies actually make it; the label on your bottle names the one that supplied yours.

Answers drafted from the FDA-approved label with AI and reviewed by our pharmacy team. How we use AI →

More about Ampicillin on HelloPharmacist

📊Ampicillin supplement interactions50 checked — ranked by severity 🌿Drug & Supplement CheckerAmpicillin vs. vitamins & herbs 💬Ask a PharmacistFree answer, usually < 24h 🔎NDC & pricing lookupFind Ampicillin NDCs & costs 🅰️Browse Drugs A–ZLook up any medication
Detailed data & references for Ampicillin Forms & strengths, pricing, billing codes, manufacturers, safety reports and sourcing — the data behind the page. Most people can stop here. Each section below opens on a tap.

Ampicillin forms and strengths (how it comes)

Ampicillin is available in 2 forms. Different forms and brands can have different approved uses, doses, schedules, and directions. Follow the instructions for your exact product, and do not switch forms without guidance from your prescriber or pharmacist.

Injection

Into a muscle · Into a vein
How this form is used
What it may be used for
  • Ampicillin injection treats moderate to severe respiratory tract infections caused by susceptible bacteria.
  • Ampicillin injection treats bacterial meningitis, serious bloodstream infections (septicemia), and endocarditis.
  • Ampicillin injection treats urinary tract and gastrointestinal infections, including typhoid fever, in patients who cannot take oral medication.
  • Ampicillin Sodium intravenous injection is indicated for the same serious bacterial infections and is prepared as an IV admixture by pharmacy.
Important instructions
  • Ampicillin injection is given by a healthcare provider into a vein (intravenously) or into a muscle (intramuscularly) — it is not self-administered at home.
  • Ampicillin Sodium intravenous injection is prepared as a pharmacy bulk package for IV admixture use only; it is not for direct injection without further dilution.
  • Doses are given at regular intervals — typically every 6 to 8 hours — as determined by the prescriber based on infection type and severity.
  • Your doctor may switch you from Ampicillin injection to oral Ampicillin capsules as soon as your condition allows.
Available strengths 11 strengths
125 mg 250 mg 250 mg/250 mg 500 mg 500 mg/500 mg 1 g
Show 5 more strengths Show fewer strengths
1 g/g 2 g 2 g/2 g 10 g 10 g/100 mL
193 FDA-listed product records ⓘ

Capsule

By mouth
How this form is used
What it may be used for
  • Ampicillin capsules treat infections of the genitourinary tract, including gonorrhea, caused by susceptible bacteria.
  • Ampicillin capsules treat respiratory tract infections caused by susceptible organisms.
  • Ampicillin capsules treat gastrointestinal infections caused by Salmonella, Shigella, and other susceptible bacteria.
  • Ampicillin capsules treat meningitis caused by N. meningitidis.
Important instructions
  • Ampicillin capsules are taken by mouth, typically every 6 to 8 hours as directed by your prescriber.
  • Take Ampicillin capsules for the full prescribed course, even if you feel better sooner.
  • Follow your prescriber's and pharmacist's guidance on whether to take Ampicillin capsules with or without food.
  • Ampicillin capsules may be appropriate for infections that are mild to moderate; your doctor may switch you from an injectable form to capsules once your condition improves.
Available strengths 2 strengths
250 mg 500 mg
13 FDA-listed product records ⓘ

Ampicillin on the U.S. market: products, makers and brands

How Ampicillin appears in the FDA’s National Drug Code Directory — including its dosage forms, strengths, brand names, manufacturers, and FDA-listed product records. These are directory records, not sales or prescription volume.

32 companies list 214 Ampicillin product records with the FDA, mostly as injection, capsule; the earliest marketing or approval year on record is 1965. Brand names on the directory include Amcill, Omnipen, Penbritin and 5 more; the rest are generics.

2
Dose forms ⓘ
32
Labelers (makers, repackagers, distributors)
2
Brand names
214
FDA-listed product records ⓘ
1965
Earliest FDA record ⓘ

FDA-listed product records by dose form (tablet variants merged) — FDA National Drug Code Directory. Record counts are not sales or prescription volume.

Also listed with the FDA, not a patient dose form: Powder (8) — bulk drug substance sold to compounders/manufacturers and multi-item kits. These aren’t counted in the dose-form total above.

Sandoz Inc20%
Medical Purchasing Solutions, LLC10%
WG Critical Care, LLC9%
Sagent Pharmaceuticals5%
Eugia US LLC5%
Methapharm Inc.4%
Other makers47%

Share of FDA-listed product records by manufacturer — FDA National Drug Code Directory. Record counts are not sales or prescription volume.

How widely Ampicillin is used (Medicaid data)

A general measure of how commonly Ampicillin is prescribed, based on Medicaid — one of the largest public drug programs. The figure below is prescriptions filled in Q1–Q4 2025, summed across every form and brand of the drug.

Think of this as a proxy for how widely Ampicillin is used, drawn from freely available public data. Medicaid is just one program — these numbers don’t include Medicare, other government coverage, or commercial and cash-pay prescriptions, so real-world use is higher than what’s shown here.

33,801
Medicaid prescriptions filled (Q1–Q4 2025)
$1M gross Medicaid reimbursement (before mandatory rebates — net cost is lower)

How commonly is Ampicillin prescribed? Of the 1,601 medications we measure, Ampicillin ranks #713 by Medicaid prescriptions — more than 55% of them.

Where Ampicillin ranks among the drugs we measure · Q1–Q4 2025 · neighbors ±5
Total prescriptions — #713 of 1,601
#708 Iron Dextran Injection 34,405 Rx #709 Penicillin G (Potassiu... 34,354 Rx #710 Loteprednol Ophthalmic 34,076 Rx #711 Loteprednol Etabonate 34,076 Rx #712 Zaleplon 33,889 Rx #713 Ampicillin 33,801 Rx #714 Gentamicin Injection 33,521 Rx #715 Benralizumab Injection 33,442 Rx #716 Ciclesonide Oral Inhal... 33,286 Rx #717 Indapamide 32,997 Rx #718 Dicloxacillin 32,884 Rx

Utilization by Ampicillin product

Pick a product to see its own Medicaid numbers. Each chip is one clinical product — a specific strength & dosage form as defined by RxNorm — with brand-name and generic versions combined.

The 500 mg oral capsule is the most-dispensed Ampicillin product — about 81% of these Medicaid prescriptions.

ampicillin 500 MG Oral Capsule Most dispensed

27,282 Medicaid prescriptions (Q1–Q4 2025) 81% of Ampicillin prescriptions shown $482,360 gross reimbursement (before rebates) ≈ $18 per prescription (gross)

Summed across the 3 of 15 listed NDC products with Medicaid activity — every brand and generic of this exact strength & form. RxNorm 308212

ampicillin 2000 MG Injection

3,558 Medicaid prescriptions (Q1–Q4 2025) 11% of Ampicillin prescriptions shown $315,884 gross reimbursement (before rebates) ≈ $89 per prescription (gross)

Summed across the 11 of 44 listed NDC products with Medicaid activity — every brand and generic of this exact strength & form. RxNorm 1721476

ampicillin 1000 MG Injection

1,751 Medicaid prescriptions (Q1–Q4 2025) 5% of Ampicillin prescriptions shown $16,807 gross reimbursement (before rebates) ≈ $9.60 per prescription (gross)

Summed across the 8 of 44 listed NDC products with Medicaid activity — every brand and generic of this exact strength & form. RxNorm 1721475

ampicillin 100 MG/ML Injectable Solution

1,087 Medicaid prescriptions (Q1–Q4 2025) 3% of Ampicillin prescriptions shown $220,550 gross reimbursement (before rebates) ≈ $203 per prescription (gross)

Summed across the 6 of 20 listed NDC products with Medicaid activity — every brand and generic of this exact strength & form. RxNorm 789980

ampicillin 500 MG Injection

123 Medicaid prescriptions (Q1–Q4 2025) <1% of Ampicillin prescriptions shown $473 gross reimbursement (before rebates) ≈ $3.84 per prescription (gross)

Summed across the 2 of 25 listed NDC products with Medicaid activity — every brand and generic of this exact strength & form. RxNorm 1721474

Shares are of the Medicaid prescriptions shown here. Product grouping follows RxNorm (the National Library of Medicine’s drug terminology), so “one product” means one strength & dosage form regardless of manufacturer. Dollar figures are gross Medicaid reimbursement before mandatory rebates — rebates (often large, especially for brand-name drugs) are confidential, so actual net cost to Medicaid is lower than shown.

Source: Medicaid State Drug Utilization Data (CMS), aggregated by generic ingredient — summed across every NDC (all brands, strengths, salt forms and dosage forms) of Ampicillin, and across all states and both fee-for-service and managed-care claims. A general popularity signal; it excludes Medicare, commercial insurance and cash prescriptions, so it is not total U.S. use. Based on the 30 of 148 listed Ampicillin NDCs with Medicaid activity.

Compare Ampicillin products

A representative set of FDA-listed product records for Ampicillin — across manufacturers, strengths, and dosage forms, grouped by form with each product’s manufacturer and how the FDA approved it. The same medicine may be made and packaged by different companies, so a single drug can have many directory entries. (It’s also why a refill can look different — a new shape, color, or box — even though it contains the same medication.)

Showing 200 of 214 products — FDA National Drug Code Directory. See every product, package size and price: browse all 214 Ampicillin NDCs →

Ampicillin recall history

A recall is when a specific batch of a medicine is pulled from the market — usually a manufacturing issue, not a problem with the drug itself. Class I is most serious, Class III least.

The FDA’s enforcement reports list one Ampicillin recall since July 2021. It is no longer listed as ongoing. A recall names specific lots from one company, so check the lot number on your own bottle rather than assuming every product is affected; your pharmacist can check whether your supply came from an affected lot.

Class II Apr 13, 2022 · Terminated · Mckesson Medical-Surgical Inc. Corporate Office
cGMP deviations: Temperature abuse
  • Ampicillin for Injection, USP, 1 g per vial, 10-count box, Rx only, Distributed by: Auromedics Pharma, NDC 55150-113-10 Lots: McKesson Medical-Surgical (MMS) is not able to identify the particular lot number received by a particular consignee for the recalled prescription products. Each letter includes the date it was distributed to customers and the dates that i… FDA record D-1009-2022 →

Source: FDA enforcement (recall) reports, via openFDA; our copy was last updated Sep 24, 2026.

RxNorm Concept Web — From Ingredient to Every Form and Strength

This page starts with one ingredient concept (IN). The branches below show its dose-form concepts (SCDF), then the available clinical drug and strength concepts (SCD). Combination products remain separate concepts with their own pages.

Ingredient (IN) Ampicillin RxCUI 733 6 dose forms · 12 strengths
  1. Dose form (SCDF) Injectable Solution RxCUI 370584 In current FDA listings
    Clinical drug / strength (SCD) 100 MG/ML RxCUI 789980
  2. Dose form (SCDF) Injectable Suspension RxCUI 1666110 In current FDA listings
    Clinical drug / strength (SCD) 250 MG/ML RxCUI 2281872 400 MG/ML RxCUI 1666111
  3. Dose form (SCDF) Injection RxCUI 1721470 In current FDA listings
    Clinical drug / strength (SCD) 125 MG RxCUI 308207 250 MG RxCUI 1721473 500 MG RxCUI 1721474 1000 MG RxCUI 1721475 2000 MG RxCUI 1721476
  4. Dose form (SCDF) Oral Capsule RxCUI 370586 In current FDA listings
    Clinical drug / strength (SCD) 250 MG RxCUI 313800 500 MG RxCUI 308212
  5. Dose form (SCDF) Oral Suspension RxCUI 370585 No current FDA listing
    Clinical drug / strength (SCD) 25 MG/ML RxCUI 313799 50 MG/ML RxCUI 308210
  6. Dose form (SCDF) Oral Tablet RxCUI 370903 No current FDA listing

Look up RxCUI 733 in the RxCUI Atlas →

RxNorm is the U.S. National Library of Medicine’s normalized drug vocabulary. Its concept hierarchy can include forms that are not currently marketed; the status on each branch compares that concept with current FDA listings. RxCUIs identify vocabulary concepts, not individual packages or manufacturers.

Ampicillin brand names

Ampicillin is sold under 8 brand names in the FDA directory — Amcill, Omnipen, Penbritin, Pfizerpen and others. A brand and its generic contain the same active ingredient; the brand name belongs to one company's product.

Amcill Omnipen Penbritin Pfizerpen Polycillin Principen Totacillin Polyflex

Who makes Ampicillin: manufacturers and labelers

32 companies list Ampicillin products with the FDA. By number of product records, the largest are Sandoz Inc, Medical Purchasing Solutions, LLC, WG Critical Care, LLC. Labelers include manufacturers and repackagers; the product in your bottle depends on which one your pharmacy stocks.

Sandoz Inc 43 Medical Purchasing Solutions, LLC 22 WG Critical Care, LLC 20 Sagent Pharmaceuticals 10 Eugia US LLC 10 Methapharm Inc. 8 Civica, Inc. 8 Aurobindo Pharma Limited 8 Henry Schein, Inc. 7 Athenex Pharmaceutical Division, LLC. 6 AuroMedics Pharma LLC 5 Armas Pharmaceuticals Inc. 5 Piramal Critical Care Inc 5 Onesource Specialty Pharma Limited 5 NorthStar Rx, LLC 5 Mylan Institutional LLC 5 Xellia Pharmaceuticals USA LLC 5 Steriscience Specialties Private Limited 4 Remedyrepack Inc. 4 Hospira, Inc 4 HF Acquisition Co LLC, DBA HealthFirst 4 Heritage Pharmaceuticals Inc. d/b/a Avet Pharmaceuticals Inc. 4 Fresenius Kabi USA, LLC 4 General Injectables and Vaccines, Inc. 3

…and 8 more on the FDA NDC directory.

Ampicillin drug class (RxNorm)

Ampicillin belongs to the Penicillin-class Antibacterial class.

Pharmacologic class Penicillin-class Antibacterial
Drug family (ATC) Penicillins with extended spectrum, Antibiotics

Classified by RxNorm RxClass — the U.S. National Library of Medicine's standardized drug-classification service (Established Pharmacologic Class from the FDA, the ATC drug family from the WHO, and mechanism of action). Reference only, not medical advice.

Sources for this Ampicillin page

Core label, product, RxNorm, safety, and utilization data on this page come from the sources identified below. AI-written, editorial, and licensed sections are labeled separately.

📄
FDA-filed drug labels (SPL) Uses, dosing, warnings & side effects from SPL records retrieved through openFDA; the linked representative set can be verified on DailyMed. ✓ Linked label effective May 23, 2023
🏭
Forms, brands & labelersAggregated from ingredient-matched FDA National Drug Code Directory product records for Ampicillin.
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Real-world reportsThe FDA Adverse Event Reporting System (FAERS), served through openFDA.
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Recalls & shortagesopenFDA drug-enforcement reports and the FDA drug-shortage database.
🧾 Clinical label set — FDA-filed SPL labels retained for Ampicillin after exact ingredient or ingredient-combination matching and applicable route/form matching
Clinical labels in scope
40
Finished products in the current FDA directory
214
Companies listing them (makers, repackagers, distributors)
32
Linked representative label ⓘ
Medical Purchasing Solutions, LLC
Linked label effective
May 23, 2023
Composite sections available
16
Linked SPL Set ID
690f1986-6da9-4787-e053-2a91aa0a2644
Linked SPL Document ID
fc600b6f-0ddf-10ff-e053-6394a90a6ba5
Open the linked representative label on DailyMed ↗
NDC package records associated with this linked SPL 1

How this page is built

HelloPharmacist combines public FDA and NLM records and does not author the underlying clinical facts. The plain-language sections are written with AI from the FDA-approved label text and reviewed by our pharmacy team before publication. Medical Purchasing Solutions, LLC is the representative DailyMed label linked for verification and dates. This is general education, not medical advice: always talk to your doctor or pharmacist about your own medicines. How we build and review drug pages →