Paclitaxel

Paclitaxel is a chemotherapy used intravenously to treat several types of cancer. The specific products and formulations approved for each use differ — always confirm which product applies to your treatment.

• Metastatic breast cancer: Paclitaxel injection (solution) and albumin-bound paclitaxel products (including Abraxane) are used after prior combination chemotherapy has failed, or if the cancer returned within 6 months of adjuvant chemotherapy.
• Node-positive breast cancer (adjuvant): Paclitaxel injection (solution) is used after surgery, given sequentially with standard doxorubicin-based chemotherapy.
• Advanced ovarian cancer: Paclitaxel injection (solution) is used as subsequent therapy; in combination with cisplatin as first-line therapy.
• Non-small cell lung cancer (NSCLC): Paclitaxel injection (solution) is used in combination with cisplatin for patients not eligible for surgery or radiation. Abraxane and albumin-bound paclitaxel products are used as first-line treatment in combination with carboplatin for patients not eligible for curative surgery or radiation.
• Metastatic adenocarcinoma of the pancreas: Abraxane and albumin-bound paclitaxel products are used as first-line treatment in combination with gemcitabine.
• AIDS-related Kaposi's sarcoma: Paclitaxel injection (solution) is used as a second-line treatment.

Paclitaxel is a microtubule inhibitor — it targets the internal scaffolding inside cells called microtubules. Normally, microtubules build up and break down in a dynamic cycle that allows cells to divide. Paclitaxel locks the microtubules in place and prevents them from breaking down, causing them to form abnormal clusters and bundles. Cancer cells get stuck mid-division and cannot replicate, which slows or stops tumor growth.

Paclitaxel is always given by intravenous (IV) infusion in a hospital or infusion clinic — never taken at home as a pill. The exact schedule depends on the specific product, the cancer being treated, and your overall health.

• Albumin-bound paclitaxel products (such as Abraxane) may be infused over 30 to 40 minutes, on schedules that vary by indication — some are given every 3 weeks, others on specific days within a multi-week cycle.
• Paclitaxel injection (solution) regimens involve longer infusion times and different cycle lengths depending on the cancer type.
• Premedication (medicines to prevent allergic reactions) is required before each dose of paclitaxel injection solution.

Your oncologist will determine your specific schedule. Never adjust or skip doses without talking to your care team first.

Paclitaxel commonly causes a range of side effects that your care team will monitor throughout treatment:

• Low white blood cell count (neutropenia) — raises your risk of serious infection
• Nerve damage causing numbness, tingling, or pain in the hands and feet (peripheral neuropathy)
• Hair loss
• Nausea, vomiting, and diarrhea
• Fatigue
• Muscle and joint pain (arthralgia/myalgia)
• Low platelet count, increasing bruising or bleeding risk
• In older adults: higher rates of nosebleeds, dehydration, peripheral swelling, and decreased appetite have been reported

Serious reactions that need immediate attention include signs of a severe allergic reaction (difficulty breathing, sudden low blood pressure, hives), signs of infection or sepsis (fever, chills), new or rapidly worsening nerve symptoms, and new breathing problems that could signal lung inflammation (pneumonitis).

• Severe bone marrow suppression: The most common serious risk is a dangerous drop in neutrophils (neutropenia), which can lead to life-threatening infection. Blood counts must be checked frequently and treatment paused if counts fall too low.
• Severe allergic reactions: Fatal anaphylaxis (extreme allergic reaction) has occurred. Premedication reduces — but does not eliminate — this risk. Anyone who has had a severe reaction must not receive paclitaxel again.
• Nerve damage (neuropathy): Significant numbness or pain in the hands or feet may require a dose reduction or treatment break.
• Sepsis: When used with gemcitabine, sepsis (a life-threatening body-wide infection response) occurred in 5% of patients — particularly in those with biliary obstruction or a biliary stent. Fever should always be reported immediately.
• Pneumonitis (lung inflammation): Occurred in 4% of patients taking albumin-bound paclitaxel with gemcitabine; some cases were fatal. Treatment must be permanently stopped if pneumonitis is confirmed.
• Liver impairment: Paclitaxel is processed by the liver. Liver disease increases drug exposure and the risk of serious side effects; dose adjustments or avoiding certain formulations may be necessary.
• Fetal harm: Paclitaxel can seriously harm an unborn baby. Effective contraception is essential during treatment and for months afterward for both men and women.

Paclitaxel is broken down by liver enzymes (CYP2C8 and CYP3A4), so drugs that affect these enzymes can meaningfully change how paclitaxel behaves in your body:

• Cisplatin: When given before paclitaxel, it can reduce paclitaxel's clearance by about a third, increasing toxicity — the sequence of administration matters.
• CYP3A4 inhibitors (e.g., ketoconazole, itraconazole, ritonavir, clarithromycin, nefazodone): may raise paclitaxel levels and increase side effect risk.
• CYP3A4 inducers (e.g., rifampin, carbamazepine): may lower paclitaxel levels, potentially reducing effectiveness.
• CYP2C8 inhibitors (e.g., gemfibrozil): may increase paclitaxel exposure.
• CYP2C8 inducers (e.g., rifampin): may decrease paclitaxel levels.
• Doxorubicin: Combination use may raise doxorubicin blood levels, increasing its toxicity.
• HIV protease inhibitors (ritonavir, saquinavir, indinavir, nelfinavir): potential interactions exist through shared metabolic pathways; clinical data are limited.

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

• Low neutrophil counts: Paclitaxel must not be started if your neutrophil count is below the required threshold — your team will test this before every dose.
• Prior severe allergic reaction to paclitaxel: Do not use paclitaxel again if you have had a serious reaction to it in the past.
• Allergy to other taxane medicines (e.g., docetaxel): Cross-reactions with albumin-bound paclitaxel products have been reported; close monitoring is required.
• Liver problems: Significant liver impairment increases drug exposure and toxicity; dose reductions may be needed, and some formulations should be avoided.
• Kidney problems: Mild to moderate kidney impairment generally does not require a starting dose adjustment for albumin-bound formulations, but your team will assess your kidney function.
• Pregnancy: Paclitaxel can cause serious fetal harm. Women of childbearing potential should use effective contraception during treatment and for at least 6 months after the last dose.
• Breastfeeding: Do not breastfeed during treatment or for 2 weeks after the last dose.
• Men with partners who could become pregnant: Use effective contraception during treatment and for at least 3 months after the last dose.
• Older adults (65+): May experience higher rates of neuropathy, bone marrow suppression, fatigue, diarrhea, and dehydration — closer monitoring is recommended.
• Children: Safety and effectiveness of albumin-bound paclitaxel products have not been established in pediatric patients.

There is no antidote for a paclitaxel overdose. The main risks of too much paclitaxel are severe bone marrow suppression, nerve damage, and mouth sores (mucositis). If an overdose is suspected, the care team will focus on managing these complications with supportive treatment.

Paclitaxel stabilizes microtubules — the internal structural filaments cells use to separate chromosomes during division — preventing them from breaking apart as they normally would. This traps cancer cells mid-division, causing abnormal bundles of microtubules to form throughout the cell cycle. The result is that cancer cells cannot complete division and are directed toward cell death.

After an IV infusion of albumin-bound paclitaxel, the drug spreads rapidly from the blood into body tissues and is highly bound to proteins in the blood (about 94%). It is primarily broken down in the liver by enzymes CYP2C8 and CYP3A4, with a terminal half-life (the time it takes for half the drug to leave the body) ranging from roughly 13 to 27 hours. Only a small fraction (about 4%) leaves the body unchanged through urine; the majority is cleared through non-kidney routes, with roughly 20% excreted in feces.

Store the vials in original cartons between 20° to 25°C (68° to 77°F). Protect from light.