Metalcaptase (Penicillamine)

Metalcaptase (penicillamine) is used in disorders where copper overload or abnormal amino‑acid metabolism requires chelation, as well as in autoimmune inflammation.

• Wilson's disease: reduces hepatic and extra‑hepatic copper stores, helping to prevent organ damage.
• Rheumatoid arthritis: decreases disease activity by modulating immune response and reducing joint inflammation.
• Cystinuria: binds cystine in urine, forming soluble complexes that lower the risk of stone formation.

• Penicillamine is a low‑molecular‑weight thiol that chelates copper and other heavy metals by forming stable, water‑soluble complexes that are excreted in urine. In rheumatoid arthritis, the drug interferes with T‑cell activation and cytokine production, leading to immunomodulation and reduced inflammatory joint damage.

Penicillamine may cause a range of adverse reactions, from mild to severe.

Common Side Effects

• Taste alteration: metallic or sour taste in the mouth.
• Gastrointestinal upset: nausea, vomiting, abdominal pain or diarrhoea.
• Skin rash: mild erythema or pruritus.
• Mild leukopenia: slight reduction in white‑blood‑cell count.
• Joint stiffness: transient increase in arthralgia.

Serious or Rare Side Effects

• Agranulocytosis: severe drop in neutrophils, increasing infection risk.
• Hepatotoxicity: significant elevation of liver enzymes or liver failure.
• Nephrotic syndrome: proteinuria with edema and hypoalbuminaemia.
• Stevens‑Johnson syndrome: severe mucocutaneous reactions.
• Aplastic anemia: pancytopenia requiring immediate medical attention.

Before initiating therapy, clinicians should assess baseline parameters and monitor patients regularly.

• Monitor copper levels: periodic measurement to guide dosage adjustments.
• Liver function tests: check baseline and repeat during treatment.
• Complete blood count: regular monitoring for leukopenia or agranulocytosis.
• Renal function: assess creatinine clearance in patients with kidney impairment.
• Hypersensitivity: discontinue if signs of allergic reaction appear.
• Store at ambient temperature: keep in the original container, protect from moisture and direct sunlight.

Penicillamine can affect the absorption or activity of several concomitant medicines.

Major Interactions (Avoid)

• Zinc supplements: compete for intestinal absorption, reducing penicillamine efficacy.
• Iron preparations: form insoluble complexes, markedly decreasing bioavailability.
• Tetracycline antibiotics: chelation reduces antibiotic absorption.
• Anticoagulants (e.g., warfarin): may enhance anticoagulant effect, increasing bleeding risk.
• Sulfonamides: increased risk of severe skin reactions.

Moderate Interactions (Monitor Closely)

• ACE inhibitors: potential additive effect on renal function.
• NSAIDs: may increase risk of nephrotoxicity.
• Diuretics: monitor electrolyte balance, especially potassium.
• Oral contraceptives: possible reduction in contraceptive effectiveness.
• Immunosuppressants: watch for additive bone‑marrow suppression.