Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0024523 (malabsorption)
 7,319 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Penicillamine exists as 2 stereoisomers, but only the D-isomer is used therapeutically. Its chemical reactivity derives from its functional groups, of which the thiol group seems the most important. It is difficult to determine penicillamine in biological fluids because of its instability, the presence of endogenous compounds with a thiol function, and the various chemical forms in which it occurs, namely reduced free penicillamine, penicillamine bound to proteins, and internal (P-S-S-P) and mixed (P-S-S-C) disulphides. The earliest assay methods (colourimetry, isotopic methods, gas-phase chromatography) were neither sensitive nor specific. High performance liquid chromatography with electrochemical detection has led to a more specific assay for D-penicillamine, with detection based on either derivatisation reactions or on electro-oxidisation of the thiol function. With dual-electrode detectors (Au/Hg) disulphides can be assayed directly. D-penicillamine is absorbed rapidly but incompletely (40 to 70%) in the intestine, with wide interindividual variations. Food, antacids and, in particular, iron reduce absorption of the drug. Its bioavailability is also dramatically decreased in patients with malabsorption states. The peak plasma concentration occurs at 1 to 3 hours after ingestion, regardless of dose, and is of the order of 1 to 2 mg/L after an oral dose of 250 mg; some investigators have reported a double peak in plasma, which is probably not due to an enterohepatic cycle. The concentration in plasma then decreases rapidly, generally following a biphasic curve. When long term treatment is discontinued, there is a slow elimination phase lasting 4 to 6 days, which suggests that there is a 'deep compartment' or 'slow pool of the drug reversibly bound to tissues', particularly the skin. This may explain the persistence of its therapeutic effect and the occurrence of undesirable side effects after treatment has been stopped. During long term treatment plasma concentrations are highly variable between individuals. They do not seem to be correlated with the activity or the toxicity of D-penicillamine in patients with rheumatoid arthritis. More than 80% of plasma D-penicillamine is bound to proteins, particularly albumin. The rest is mainly in the free reduced form or as disulphides. Only a small portion of the dose is metabolised in the liver to S-methyl-D-penicillamine. The route of elimination is mainly renal; disulphides represent the main compounds found in the urine. Faecal excretion corresponds mainly to the non-absorbed fraction of the drug.
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PMID:Clinical pharmacokinetics of D-penicillamine. 331 47

Systemic sclerosis is an extremely variable disease in its manifestations and consequently, treatment needs to be individualized depending on the specific problems that each patient has. Limited scleroderma patients have a prolonged duration of Raynaud's phenomenon and puffy fingers before they develop any skin thickening, digital ulcers or gastrointestinal symptoms. They are likely to present with all the classic manifestations of scleroderma. Diffuse scleroderma patients have a much more acute systemic onset with marked whole hand swelling and may initially have only subtle skin thickening. A good understanding of the differences between the natural history of limited and diffuse scleroderma will enable the physician to treat present problems and anticipate future ones more effectively. One should determine which major subset and organ systems are involved before deciding on the appropriate therapy. Advances in organ-specific therapy, particularly calcium channel antagonists in Raynaud's phenomenon, proton pump inhibitors in esophageal reflux, intravenous iloprost and endothelin receptor antagonists in pulmonary hypertension, and ACE inhibitors in renal crisis, have decreased morbidity and mortality in patients with scleroderma. Studies of aggressive therapies to prevent or improve pulmonary fibrosis are in progress. Further clinical experience in wound healing, gastrointestinal malabsorption and physical therapy for loss of motion has helped patients to have a more comfortable life. In recent years, a significant number of controlled clinical trials have been performed and there has been improved understanding of the best way to perform studies and of which patients are most likely to respond to therapy. Penicillamine, methotrexate, photopheresis, relaxin, interferons, and cyclosporine have all been studied in controlled trials with variable outcomes. Although an overall remittive therapy has not yet been determined, new, potentially useful agents are being investigated.
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PMID:Treatment of systemic sclerosis. 1172 50