Porphyria drug contraindications

Hydroxychloroquine is approved for the treatment of both systemic and cutaneous lupus erythematosus. Both chloroquine and quinacrine (Atabrine) are also effective in this skin disease. Low-dose chloroquine is used for the therapy of porphyria cutanea tarda in patients in whom phlebotomy has failed or is contraindicated. Other skin diseases in which the drugs are useful (after sunscreens and avoidance of sun exposure) include polymorphous light eruption and solar urticaria. 

Precautions As noted previously, barbiturates induce the P-450 system and therefore may decrease the effect of drugs that are metabolized by these hepatic enzymes. Barbiturates increase porphyrin synthesis, and are contraindicated in patients with acute intermittent porphyria. 

Only phenobarbital strongly induces the synthesis of the hepatic cytochrome P-450 drug metabolizing system. Phenobarbital is contraindicated in the treatment of acute intermittent porphyria. Buspirone lacks the anticonvulsant and muscle-relaxant properties of the benzodiazepines and causes only minimal sedation, v ... 

Most antiepUeptic drugs are contraindicated in acute intermittent porphyrias. 

Hepatic metabolism (some to active metabolites). Induction of cytochrome P450s is characteristic and may lead to drug interactions. Because of T heme synthesis, they are contraindicated in porphyrias. 

The barbiturates induce drug-metabolizing enzymes, including the P450 system, leading to potential drug interactions. They also stimulate heme synthesis and are contraindicated in porphyrias. 

Pentobarbital is contraindicated in patients with bronchopneumonia, status asthmaticus, or severe respiratory distress because of the potential for respiratory depression. It should not be used in patients who are depressed or have suicidal ideation because the drug can worsen depression in patients with uncontrolled acute or chronic pain because exacerbation of pain and paradoxical excitement can occur or in patients with porphyria because the drug can trigger symptoms of this disease. Pentobarbital should be used cautiously in patients who must perform hazardous tasks requiring mental alertness because the drug causes drowsiness. 

Short-term administration of barbiturates has no clinically significant effect on the hepatic, renal, or endocrine systems. A single induction dose of thiopental does not alter tone of the gravid uterus, but may produce mild transient depression of newborn activity. Drug-induced histamine release is occasionally seen. Barbiturates can induce fatal attacks of porphyria in patients with acute intermittent or variegate porphyria and are contraindicated in such patients. Unlike inhala-tional anesthetics and succinylcholine, barbiturates and all other parenteral anesthetics apparently do not trigger malignant hyperthermia. 

Sulfasalazine is used for the treatment of mild to moderate ulcerative colitis as adjunct therapy in the treatment of severe ulcerative colitis, for the treatment of Crohn s disease, and for the treatment of rheumatoid arthritis or ankylosing spondylitis. Contraindications include hypersensitivity to sulfa drugs, salicylates, intestinal or urinary obstruction, and porphyria. 

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