D-penicillamine is an chelating agent derived as an α-amino acid metabolite of penicillin.
This drug chelates a variety of metals, including copper, lead, iron, and mercury, forming stable water soluble complexes that are excreted by the kidneys. It also combines chemically with cystine to form a stable, soluble complex that can be readily excreted.
Penicillamine has antirheumatic activity, the exact mechanisms of which is not understood, but the drug apparently improves lymphocyte function, decreases IgM rheumatoid factor and immune complexes in serum and synovial fluid.
Although penicillamine is a degradation product of penicillins, it has no antimicrobial activity.
It is primarily used in chronic hepatitis cases associated with copper toxicity, including
- Copper-associated hepatitis of Labrador Retrievers
- Acidophil hepatitis
- Chronic Hepatitis of Bedlington Terriers
- Chronic Hepatitis of West Highland White Terriers
- Idiopathic Chronic Hepatitis
- Chronic Hepatitis of Doberman Pinschers
The most prevalent adverse effect associated with penicillamine is nausea and vomiting.
Recommended dose rate in dogs is:
- For copper-associated hepatopathy:
- - a) 10 - 15 mg/kg PO bid on an empty stomach. Only effective for long-term use, not for acute copper toxicity.
- - b) For Bedlington Terriers: Initially at 125 mg q12h PO. If anorexia and vomiting are significant problems, start dose at 125 mg daily and increase to 125 mg bid over several days.
- - c) 125 - 250 mg PO 30 minutes prior to feeding. If vomiting occurs, divide daily dosage into bid - tid.
- For cystine urolithiasis:
- - a) 15 mg/kg PO twice daily. If nausea and vomiting occur, mix with food or give at mealtime. Some dogs may need to have the dosage slowly increased to full dose in order to tolerate the drug. (Osborne, Hoppe, and O'Brien 1989)
- - b) 15 mg/kg PO bid with food
- For lead poisoning:
- - a) After initial therapy regimen with CaEDTA and if continued therapy is desired at home, may give penicillamine at 110 mg/kg/day PO divided q6-8h for 1-2 weeks. If vomiting, depression, and anorexia occur, may reduce dose to 33 - 55 mg/kg/day divided q6-8h which should be better tolerated.
- - b) As an alternate or adjunct to CaEDTA: 30 - 110 mg/kg/day divided qid for 7 days; may repeat after 7 days off therapy. If vomiting occurs, may give dimenhydrinate at 2 - 4 mg/kg PO 1/2 hour before penicillamine dose.