Paclitaxel is a novel anti-microtubule agent that promotes the assembly of microtubules from tubulin dimers and stabilizes microtubules by preventing depolymerization. This stability results in the inhibition of the normal dynamic reorganization of the microtubule network that is essential for vital interphase and mitotic cellular functions. In addition, paclitaxel induces abnormal arrays or “bundles” of microtubules throughout the cell cycle and multiple asters of microtubules during mitosis. Following intravenous administration of Paclitaxel, paclitaxel plasma concentrations declined in a biphasic manner. The initial rapid decline represents distribution to the peripheral compartment and elimination of the drug. The later phase is due, in part, to a relatively slow efflux of paclitaxel from the peripheral compartment.

Ovarian Carcinoma: Paclitaxel is indicated as first line and subsequent therapy for the treatment of advanced carcinoma of the ovary. As first line therapy, Paclitaxel is indicated in combination with cisplatin.

Breast Carcinoma: Paclitaxel is indicated for the adjuvant treatment of node-positive breast cancer administered sequentially to standard doxorubicin-containing combination chemotherapy. Paclitaxel is indicated for the treatment of breast cancer after failure of combination chemotherapy for metastatic disease or relapse within 6 months of adjuvant chemotherapy. Prior therapy should have included an anthracline unless clinically contraindicated. Paclitaxel is indicated for the first-line therapy of advanced or metastatic breast cancer either in combination with an anthracycline in patients for whom anthracline therapy is suitable or in combination with trastuzumab in patients who overexpress HER2 at a 2+ or 3+ level as determined by immuno-histochemistry.

Gemcitabine, in combination of Paclitaxel, is indicated in the treatment of patients with unresectable, locally recurrent or metastatic breast cancer who have relapsed following adjuvant/neoadjuvant chemotherapy. Prior chemotherapy should have included an anthracycline unless clinically contraindicated.

Paclitaxel is indicated for the treatment of metastatic cancer of the breast, in combination with trastuzumab, in patients who have tumors that over-express HER2 and who have not received previous chemotherapy for their metastatic disease.

Non-Small Cell Lung Carcinoma: Paclitaxel, in combination with cisplatin, is indicated for the first line treatment of non-small cell lung cancerin patients who are not candidates for potential curative surgery and/or radiation therapy.

Kaposi's Sarcoma: Paclitaxel is indicated for the second line treatment of AIDS related Kaposi's Sarcoma.

Gastric Carcinoma: Paclitaxel is indicated for the treatment of Gastric Carcinoma.

All patients should be premedicated prior to Paclitaxel administration in order to prevent severe hypersensitivity reactions. Such premedication may consist of dexamethasone 20 mg PO administered approximately 12 and 6 hours before Paclitaxel, diphenhydramine (or its equivalent) 50 mg IV 30 to 60 minutes prior to Paclitaxel, and cimetidine (300 mg) or ranitidine (50 mg) IV 30 to 60 minutes before Paclitaxel.

First-line treatment of ovarian cancer: Although alternative medication regimens for paclitaxel are under investigation at present, a combination therapy of paclitaxel and cisplatin is recommended. Depending on the duration of infusion, two different dosages are recommended for paclitaxel treatment: 175 mg/m2 of paclitaxel is administered as an intravenous infusion over a period of three hours followed thereafter by 75 mg/m2 of cisplatin and the therapy is repeated at 3-week intervals, or 135 mg/m2 of paclitaxel is administered as an intravenous infusion over a period of 24 hours followed thereafter by 75 mg/m2 of cisplatin and the therapy is repeated at 3-week intervals.

Second-line treatment of ovarian cancer: The recommended dose of paclitaxel is 175 mg/m2 administered over 3 hours, with a 3-week interval between courses.

Adjuvant chemotherapy in breast carcinoma: The recommended dose of paclitaxel is 175 mg/m2 administered over a period of 3 hours every 3 weeks for four courses, following AC therapy.

First-line chemotherapy of breast carcinoma: When used in combination with doxorubicin (50 mg/m2), paclitaxel should be administered 24 hours after doxorubicin. The recommended dose of paclitaxel is 220 mg/m2 administered intravenously over a period of 3 hours, with a 3-week interval between courses. When used in combination with trastuzumab, the recommended dose of paclitaxel is 175 mg/m2 administered intravenously over a period of 3 hours, with a 3-week interval between courses. Paclitaxel infusion may be started the day following the first dose of trastuzumab or immediately after the subsequent doses of trastuzumab if the preceding dose of trastuzumab was well tolerated.

Second-line chemotherapy of breast carcinoma: The recommended dose of paclitaxel is 175 mg/m2 administered over a period of 3 hours, with a 3-week interval between courses.

Advanced non-small-cell lung cancer: The recommended dose of paclitaxel is 175 mg/m2 administered over 3 hours followed by 80 mg/m2 of cisplatin, with a 3-week interval between courses.

Treatment of AIDS-related KS: The recommended dose of paclitaxel is 100 mg/m2 administered as a 3-hour intravenous infusion every two weeks.

Dose adjustment: Subsequent doses of paclitaxel should be administered according to individual patient tolerance. Paclitaxel should not be re-administered until the neutrophil count is >1.5 x 109/1 (>1 x 109/1 for KS patients) and the platelet count is >100 x 109/1 (>75 x 109/1 for KS patients).

• Paclitaxel is contraindicated in patients with severe hypersensitivity reactions to paclitaxel, macrogolglycerol ricinoleate (polyoxyl castor oil.)
• Paclitaxel is contraindicated during lactation.
• Paclitaxel should not be used in patients with baseline neutrophils <1.5x10⁹/I (<1x10⁹/I for KS patients) or platelets <100x10⁹/I (<75x10⁹/I for KS patients).
• In KS, paclitaxel is also contraindicated in patients with concurrent, serious, uncontrolled infections.
• Patients with severe hepatic impairment must not be treated with paclitaxel.

Common: Low blood counts leading to increased risk for infection, anemia and/or bleeding, hair loss, arthralgias and myalgias, pain in the joints and muscles, peripheral neuropathy, nausea, vomiting (usually mild), diarrhea, Mouth sores, hypersensitivity reaction, fever, facial flushing, chills, shortness of breath, or hives after paclitaxel is given.

Rare: swelling of the feet or ankles (edema), liver problems, low blood pressure, darkening of the skin where previous radiation treatment has been given.

Overdose Effects

There is no known antidote for paclitaxel overdose. In case of overdose, the patient should be closely monitored. Treatment should be directed at the primary anticipated toxicities, which consist of bone marrow suppression, peripheral neurotoxicity and mucositis. Overdoses in paediatric patients may be associated with acute ethanol toxicity.

Paclitaxel should be administered under the supervision of a physician experienced in the use of cancer chemotherapeutic agents. Since significant hypersensitivity reactions may occur, appropriate supportive equipment should be available. Given the possibility of extravasation, it is advisable to closely monitor the infusion site for possible infiltration during drug administration. Paclitaxel should be given before cisplatin when used in combination.

Significant hypersensitivity reactions, as characterised by dyspnoea and hypotension requiring treatment, angioedema, and generalised urticaria have occurred in <1% of patients receiving paclitaxel after adequate premedication. Fatal hypersensitivity reactions have occurred in patients despite premedication. These reactions are probably histamine-mediated. In the case of severe hypersensitivity reactions, paclitaxel infusion should be discontinued immediately.

Bone marrow suppression, primarily neutropenia, is the dose-limiting toxicity. Neutrophil nadirs occurred at a median of 11 days. Frequent monitoring of blood counts should be instituted. Patients should not be retreated until the neutrophil count is ≥1.5 x 109/1 (≥1 x 109/1 for KS patients) and the platelets recover to ≥100 x 109/1 (≥75 x 109/1 for KS patients).

Severe cardiac conduction abnormalities have been reported rarely with single agent paclitaxel. If patients develop significant conduction abnormalities during paclitaxel administration, appropriate therapy should be administered and continuous cardiac monitoring should be performed during subsequent therapy with paclitaxel.

Use in Special Populations

Patients who experience severe neutropenia: (neutrophil count <0.5 x 109/1 for a minimum of 7 days) or severe peripheral neuropathy, should receive a dose reduction of 20% for subsequent courses (25% for KS patients).

Patients with hepatic impairment: Inadequate data are available to recommend dosage alterations in patients with mild to moderate hepatic impairments. Patients with severe hepatic impairment must not be treated with paclitaxel.

Pediatric use: Paclitaxel is not recommended for use in children below 18 years due to lack of data on safety and efficacy

Pregnancy & Lactation

Pregnancy Category D. There is no adequate data from the use of paclitaxel in pregnant women, however as with other cytotoxic medicinal products, paclitaxel may cause foetal harm when administered to pregnant women. Paclitaxel is contraindicated during lactation.