1. Clinical Overview
Doxorubicin (Liposomal) is a pegylated, liposomal formulation of the anthracycline antibiotic doxorubicin. It is designed to encapsulate doxorubicin within liposomes, which are microscopic vesicles composed of a phospholipid bilayer. This encapsulation significantly alters the pharmacokinetics and biodistribution compared to conventional doxorubicin. The pegylated (stealth) coating helps evade detection by the mononuclear phagocyte system, leading to prolonged circulation time and preferential accumulation in tumor tissues with leaky vasculature, a phenomenon known as the Enhanced Permeability and Retention (EPR) effect. This results in higher intratumoral concentrations and reduced exposure to healthy tissues, particularly the heart, thereby mitigating the risk of cardiotoxicity. It is a cytotoxic, non-cell-cycle specific antineoplastic agent.
| Onset | Duration | Bioavailability |
|---|---|---|
| The onset of cytotoxic action begins immediately upon cellular uptake and intercalation into DNA. However, clinical therapeutic effects (e.g., tumor shrinkage) are typically observed over several weeks to months of treatment cycles. | The pharmacological effect persists for the duration of the cell cycle disruption and DNA damage. The liposomal formulation has a significantly prolonged plasma half-life (approx. 55 hours) compared to conventional doxorubicin (approx. 20 minutes), allowing sustained exposure. | Not applicable. Administered exclusively via intravenous infusion; systemic bioavailability is considered 100% post-IV administration. |
2. Mechanism of Action
The liposomal formulation delivers doxorubicin to tumor sites. Once internalized by tumor cells, doxorubicin exerts multiple cytotoxic effects: 1) **Intercalation into DNA:** It inserts itself between base pairs of the DNA double helix, disrupting DNA and RNA synthesis. 2) **Topoisomerase II Inhibition:** It stabilizes the topoisomerase II-DNA complex, preventing religation of DNA strands and causing double-strand breaks. 3) **Generation of Reactive Oxygen Species (ROS):** Through redox cycling, it generates semiquinone free radicals and superoxide anions, leading to oxidative damage of cellular membranes, proteins, and DNA. 4) **Disruption of Cellular Membranes:** It binds to cell membrane lipids, altering fluidity and function.
3. Indications & Uses
- AIDS-related Kaposi's sarcoma (in patients with low CD4 counts and extensive mucocutaneous disease)
- Ovarian Cancer (platinum-refractory)
- Multiple Myeloma (in combination with bortezomib, for patients who have not previously received bortezomib and have received at least one prior therapy)
4. Dosage & Administration
Adult Dosage: Dose is based on Body Surface Area (BSA). **Kaposi's Sarcoma:** 20 mg/m² IV over 30 minutes, every 2-3 weeks. **Ovarian Cancer:** 50 mg/m² IV over 60 minutes, every 4 weeks. **Multiple Myeloma:** 30 mg/m² IV over 60 minutes on day 4 following bortezomib (which is given on days 1, 4, 8, & 11 of a 21-day cycle). Dose adjustments are based on hematological and non-hematological toxicity.
Administration: **FOR IV INFUSION ONLY. NOT FOR INTRAMUSCULAR, SUBCUTANEOUS, OR INTRATHECAL USE. FATAL IF GIVEN INTRATHECALLY.** 1. Handle with cytotoxic precautions (gloves, gown, eye protection). 2. Dilute prescribed dose in 250 mL of 5% Dextrose Injection (D5W). **DO NOT USE SALINE or any other diluent.** 3. Do not mix with other drugs or heparin. Use a separate line. 4. Administer using a controlled infusion device over 30-60 minutes as per indication. 5. Use an IV line with a free-flowing IV solution (D5W) to prevent extravasation. Avoid veins over joints or in limbs with compromised circulation. 6. Observe for infusion reactions (flushing, shortness of breath, back pain). Pre-medication with antihistamines and corticosteroids is common.
5. Side Effects
Common side effects may include:
- Myelosuppression: Anemia, Leukopenia (Neutropenia), Thrombocytopenia
- Nausea and Vomiting (less severe than conventional doxorubicin)
- Stomatitis/Mucositis
- Alopecia (reversible, less frequent than conventional)
- Fatigue/Asthenia
- Palmar-Plantar Erythrodysesthesia (PPE) or Hand-Foot Syndrome - a characteristic toxicity of this formulation
- Constipation or Diarrhea
- Anorexia
- Skin rash/itching
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Other Cardiotoxic Agents (e.g., Trastuzumab, Cyclophosphamide, Daunorubicin) | Markedly increased risk of cardiomyopathy and congestive heart failure. Avoid concurrent use or monitor LVEF very closely. | Major |
| Cyclosporine, Verapamil | May increase intracellular doxorubicin concentrations, enhancing both efficacy and toxicity (especially hematological). | Moderate |
| Phenobarbital, Phenytoin | May increase hepatic metabolism of doxorubicin, reducing its plasma concentration and efficacy. | Moderate |
| Live Vaccines (e.g., MMR, Varicella, Yellow Fever) | Risk of disseminated infection due to immunosuppression. Contraindicated during treatment. | Major |
| Drugs metabolized by CYP2D6, CYP3A4 | Doxorubicin may inhibit these enzymes, increasing levels of substrates (e.g., some beta-blockers, antidepressants). | Moderate |
7. Patient Counselling
- DO report any signs of infection (fever, chills, sore throat) immediately.
- DO maintain good oral hygiene to reduce risk of mucositis.
- DO use sunscreen and protective clothing, as skin may be more sensitive to sun.
- DO drink plenty of fluids unless contraindicated.
- DO NOT receive any vaccinations without consulting your oncologist.
- DO NOT become pregnant or father a child during and for specified months after treatment. Use effective contraception.
- DO NOT handle the medication vials or infusion lines if you are a caregiver. Leave it to healthcare professionals.
8. Toxicology & Storage
Overdose: Exacerbation of acute toxicities: Severe myelosuppression (pancytopenia, infection, hemorrhage), severe mucositis, gastrointestinal bleeding, and acute cardiotoxicity (acute LV failure, arrhythmias).
Storage: Store unopened vials in a refrigerator at 2°C to 8°C. **DO NOT FREEZE.** Protect from light. Keep in original carton. The diluted solution in D5W is stable for up to 24 hours under refrigeration (2°C to 8°C). Do not store partially used vials. Discard any unused portion. Handle as cytotoxic waste. Must be dispensed and stored in a designated area for hazardous drugs.