Melphalan: Uses, Dosage, Side Effects, and Warnings

Introduction

Melphalan is a potent chemotherapeutic agent used in the treatment of various cancers, including multiple myeloma, malignant lymphoma, and ovarian carcinoma. As an alkylating agent, melphalan interferes with cancer cell growth by damaging DNA and preventing cell division. This article provides a comprehensive overview of melphalan, its uses, dosage, side effects, and warnings.

Chemical Composition and Properties

Melphalan, also known as L-phenylalanine mustard or L-PAM, is a phenylalanine derivative of nitrogen mustard. Its chemical formula is C ₁₃H ₁₈Cl ₂N ₂O ₂, and it has a molecular weight of 305.2 g/mol. Melphalan is a white to off-white crystalline powder that is soluble in water and alcohol.

The mechanism of action of melphalan involves the formation of interstrand DNA crosslinks, which prevent DNA replication and lead to cell death. This action is particularly effective against rapidly dividing cells, such as cancer cells [1].

Pharmacology

Pharmacokinetics

After oral administration, melphalan is rapidly absorbed from the gastrointestinal tract, with peak plasma concentrations occurring within 1-2 hours. The drug undergoes extensive first-pass metabolism in the liver, resulting in a bioavailability of approximately 30-50%. Melphalan is distributed throughout the body and has a volume of distribution of 0.5 L/kg [2].

Pharmacodynamics

Melphalan exerts its cytotoxic effects by forming interstrand DNA crosslinks, which prevent DNA replication and lead to cell death. The drug is cell cycle non-specific but is most active against rapidly dividing cells, such as those found in tumors. Melphalan also has immunosuppressive properties, which may contribute to its therapeutic effects [1].

Medical Uses

Melphalan is indicated for the treatment of several cancers, including:

• Multiple myeloma
• Malignant lymphoma
• Lymphoblastic lymphoma
• Ovarian carcinoma
• Uveal melanoma with unresectable hepatic metastases

In multiple myeloma, melphalan is often used in combination with prednisone or as part of a high-dose regimen followed by autologous stem cell transplantation [1].

Administration Routes

Melphalan can be administered via several routes, including:

• Intra-arterial route
• Intravenous (IV) route
• Oral administration

The choice of administration route depends on the specific indication and patient factors.

Dosage and Administration Guidelines

The dosage of melphalan varies depending on the indication, administration route, and individual patient factors. Standard dosages for oral administration range from 0.18-0.25 mg/kg daily for 4-7 days, repeated every 4-6 weeks. High-dose regimens, used in the context of autologous stem cell transplantation, may involve doses of 140-200 mg/m ² administered intravenously [2].

Brand Names and Formulations

Melphalan is available under the brand name Alkeran and as a generic drug. It is supplied as tablets for oral administration and as a powder for injection for intravenous or intra-arterial use.

Side Effects

Common side effects of melphalan include:

• Nausea
• Vomiting
• Loss of appetite
• Diarrhea
• Mouth sores
• Hair loss
• Fatigue
• Increased risk of infections

Severe side effects may include bone marrow suppression, leading to anemia, thrombocytopenia, and neutropenia. Long-term use of melphalan may increase the risk of secondary malignancies, such as acute leukemia [2].

Interactions

Melphalan may interact with several drugs, including:

• Live vaccines
• Nalidixic acid
• Cimetidine
• Cyclosporine

Patients should inform their healthcare provider about all medications, supplements, and herbal products they are taking before starting melphalan therapy.

Contraindications and Precautions

Melphalan is contraindicated in patients with a history of hypersensitivity to the drug or any of its components. It should be used with caution in patients with bone marrow suppression, renal impairment, or a history of allergic reactions to other alkylating agents.

Women who are pregnant or breastfeeding should not use melphalan due to the potential for fetal harm and the presence of the drug in breast milk. Patients undergoing melphalan therapy should use effective contraception to avoid pregnancy [2].