Phendimetrazine

Phendimetrazine tartrate is a prescription weight-loss aid approved for short-term use in adults with obesity. Here is what the available products are approved for:

• Phendimetrazine Tartrate extended-release capsules are indicated for adults with a BMI of 30 or higher, or a BMI of 27 or higher when additional risk factors like high blood pressure, diabetes, or high cholesterol (hyperlipidemia) are present, who have not responded adequately to diet and exercise alone.
• Phendimetrazine Tartrate tablets are indicated for adults with a BMI of 30 or higher who have not responded to diet and/or exercise alone.
• Both forms are approved only as a short-term addition (a few weeks) to a calorie-restricted diet — not as a standalone solution.
• Both forms are approved for use as monotherapy only — they must never be combined with other weight-loss drugs or stimulants.

Phendimetrazine is a sympathomimetic amine — a stimulant that mimics the effects of adrenaline-like chemicals in the body. It acts on the central nervous system similarly to amphetamines. It belongs to a class of drugs called anorectics, which are thought to reduce appetite, though the exact mechanism behind its weight-loss effect isn't fully established. Other actions on the brain or metabolism may also contribute.

The drug raises blood pressure and can increase heart rate as part of its stimulant effect. Tolerance to its appetite-suppressing action tends to develop within a few weeks, which is why it's only intended for short-term use.

Phendimetrazine tartrate comes in two oral forms with different dosing schedules — do not interchange them without your prescriber's guidance.

• Tablets: Generally taken two to three times a day, about one hour before meals. Your prescriber will adjust the dose to find what works best for you.
• Extended-release capsules (Phendimetrazine Tartrate): Taken once in the morning, 30 to 60 minutes before the morning meal. Do not take it later in the day, as it can disrupt sleep.

Always follow your prescriber's exact instructions. If you feel the medication is no longer working, do not increase your dose — talk to your doctor instead.

Like all stimulant medications, phendimetrazine can cause a range of side effects. Common ones include:

• Dry mouth
• Trouble sleeping (insomnia)
• Restlessness, agitation, or overstimulation
• Rapid or pounding heartbeat (palpitations or tachycardia)
• Elevated blood pressure
• Dizziness, tremor, or headache
• Nausea, stomach pain, diarrhea, or constipation
• Sweating, flushing, or blurred vision
• Urinary frequency or changes in libido

More serious reactions — including pulmonary hypertension (high pressure in the lung arteries), heart valve problems, psychosis, and severe withdrawal after stopping suddenly — require immediate medical attention. Contact your doctor or seek emergency care if you notice chest pain, shortness of breath, fainting, leg swelling, hallucinations, or extreme mood changes.

• Pulmonary hypertension risk: Use of phendimetrazine has been linked to pulmonary hypertension — a rare but often fatal condition. The risk is significantly higher with more than three months of use. Stop taking it and see your doctor immediately if you develop shortness of breath during activity, chest pain, fainting, or leg swelling.
• Heart valve concerns: Some anorectic drugs have been associated with heart valve damage. While no cases have been reported with phendimetrazine used alone, your doctor may recommend a cardiac evaluation before and during treatment.
• Abuse and dependence potential: This medication is a stimulant with real potential for misuse. Do not take more than prescribed, and do not use it if you have a history of drug abuse.
• Withdrawal: Stopping suddenly after prolonged high-dose use can cause severe fatigue and depression. Talk to your doctor before stopping.
• Impaired alertness: Phendimetrazine can affect your ability to drive or operate machinery safely — be cautious until you know how it affects you.
• Short-term use only: If you haven't lost at least 4 pounds after 4 weeks, your doctor should reassess whether to continue treatment.

Phendimetrazine interacts with several drugs and substances — always give your prescriber and pharmacist a full list of everything you take.

• MAO inhibitors (e.g., phenelzine, tranylcypromine): Combining these with phendimetrazine can trigger a hypertensive crisis — a dangerous, potentially life-threatening spike in blood pressure. Do not take phendimetrazine within 14 days of stopping an MAO inhibitor.
• Alcohol: Drinking alcohol while on phendimetrazine can cause an adverse reaction — avoid it.
• Insulin and oral diabetes medications: Your need for diabetes medication may change while on phendimetrazine — monitor your blood sugar closely and tell your doctor.
• Adrenergic neuron blocking drugs (some blood pressure medications): Phendimetrazine can reduce their blood-pressure-lowering effect, potentially making your blood pressure harder to control.
• Other weight-loss drugs, stimulants, or herbal diet products: Combining these with phendimetrazine is contraindicated and increases the risk of serious side effects.

This is not a complete list of interactions. Always talk with your doctor or pharmacist before starting, stopping, or changing any medication.

• Do not take phendimetrazine if you have a history of heart disease, coronary artery disease, stroke, heart failure, arrhythmias (abnormal heart rhythms), uncontrolled high blood pressure, or pulmonary hypertension.
• Do not take it if you have glaucoma (increased eye pressure), an overactive thyroid (hyperthyroidism), or agitated states.
• Do not take it if you have a history of drug abuse — this medication has abuse potential.
• Do not take it if you are pregnant or breastfeeding.
• Tell your doctor if you have a known heart murmur or valvular heart disease — phendimetrazine is not recommended in these cases.
• Tell your doctor if you have diabetes — your insulin or oral medication needs may change.
• Do not use phendimetrazine if you have taken any other anorectic (weight-loss) drug within the past year.
• Tell your doctor about all medications you take — prescription, over-the-counter, and herbal — before starting phendimetrazine.

Taking too much phendimetrazine can cause serious symptoms, including extreme restlessness, confusion, hallucinations, panic, rapid or irregular heartbeat, very high or very low blood pressure, nausea, vomiting, seizures, coma, and in severe cases, death. If you suspect an overdose, call 911 or Poison Control (1-800-222-1222 in the US) immediately.

Phendimetrazine stimulates the central nervous system and raises blood pressure, acting similarly to amphetamines. It is classified as an anorectic — a drug that reduces appetite — though appetite suppression may not be its only weight-loss mechanism. It can also cause rapid heart rate (tachycardia). Tolerance to its appetite-reducing effect typically develops within a few weeks of regular use.

Phendimetrazine is eliminated mainly through the kidneys, with most of the drug and its breakdown products excreted in urine. It is partially metabolized into phenmetrazine and phendimetrazine-N-oxide. The average elimination half-life — the time it takes the body to clear half the drug — is about 3.7 hours for both the tablet and extended-release capsule forms. The tablet is absorbed more quickly than the extended-release capsule, which releases the drug gradually over time.