Penicillamine (D-Penicillamine)

Mechanism

Pharmacological Group and Molecular Target

Heavy metal chelating agent for exclusive oral administration.

Detailed Mechanism of Action

Penicillamine is a hydrophilic amino acid metabolite derived from the hydrolytic degradation of penicillin that lacks intrinsic antibacterial properties. It has a free reactive sulfhydryl group on its linear dithiol molecule that acts as a high coordination affinity binding site for divalent and trivalent metals, especially copper (Cu²⁺), mercury (Hg²⁺) and lead (Pb²⁺). The resulting inert and highly soluble metal-penicillamine complex is rapidly captured in the bloodstream and cleared from the body at the renal level through passive glomerular filtration, increasing urinary excretion of the metal.

Indicators and dose

Specific Clinical Indications

• Treatment of Wilson's disease (hepatolenticular degeneration) characterized by a massive toxic accumulation of copper in the liver and in the nuclei of the brain base.
• Adjuvant treatment of mild chronic lead or mercury poisoning when parenteral therapy with edetate or dimercaprol is not indicated or has been terminated.

Dosage Scheme and Infusion Protocols

• Wilson's Disease (Adults): 250 mg to 500 mg orally four times a day (1 g to 1.5 g daily) given strictly on an empty stomach (1 hour before or 2 hours after meals), as food and iron or calcium supplements dramatically interfere with its absorption.
• Mandatory Supplementation: Systematic co-administration of 25 mg daily of Pyridoxine (Vitamin B6) orally is required, given that penicillamine directly inactivates and accelerates renal elimination of the pyridoxine cofactor, with the consequent risk of inducing severe peripheral neuropathy.

Security

Contraindications and Precautions

• Crossed Clinical Allergies: Patients with a history of anaphylaxis or severe immediate IgE-mediated allergy to penicillin. There is a theoretical risk of immunological cross-reactivity due to its biosynthetic structural origin.
• Hematological Bone Marrow Suppression: It is associated with severe neutropenia, severe thrombocytopenia or reversible aplastic anemia. Weekly complete blood counts are required during the initiation of therapy.