[The attack of acute porphyria]. / Genetik och metabola förlopp bakom den akuta porfyriattacken - Mer än hundra läkemedel är potentiellt livshotande vid akut porfyri.

The attack of acute porphyria Based on in silico evidence of pharmacokinetic, pharmacodynamic, and physiologic properties, have approximately 1 300 medicinal drugs been assessed with regard to the specific risk to carriers of acute porphyria. The classifications have been published in booklet form, together with prophylactic advice to the carriers and suggestions for doctors in charge of their care. The risk-classifications rest on the behavior of the drug in an extended molecular model of the attack of acute porphyria. In this, symptoms are effects of 5-aminolevulinate (ALA) produced in surplus after acceleration of enzyme-deficient heme biosynthesis, taking place during induction of drug-metabolizing cytochromes P450 and triggered by hepatocellular nuclear receptors, activated by the drug. The process is enhanced by glucagon- and sirtuin-dependent molecular processes activated in stress and cellular energy deficit, and enhanced and prolonged by auto-generating ALA.

Drugs in porphyria: From observation to a modern algorithm-based system for the prediction of porphyrogenicity.

The acute porphyrias are a group of disorders which result from inherited defects in the enzymes of the heme biosynthetic pathway. Affected patients are prone to potentially fatal acute attacks. These attacks are frequently precipitated by exposure to commonly used drugs. Correctly identifying the safety or otherwise of drugs in porphyria is therefore important. In this review we describe how clinical experience and the findings of experimental systems using whole animal or cell culture models have been interpreted to determine porphyrogenicity, that is the potential of a drug to induce an acute attack in a patient carrying a gene for acute porphyria. It is now well established that induction of delta-aminolevulinic acid synthase, the rate controlling enzyme of the heme biosynthetic pathway, is fundamental to porphyrogenicity, and that drug-induced hepatic heme depletion via induction or suicidal inactivation of cytochrome P450 is central to this process. The process is now sufficiently well understood that prediction of porphyrogenicity from structural and functional information alone would appear to be justified.

Guide to drug porphyrogenicity prediction and drug prescription in the acute porphyrias.

AIMS: This paper addresses two common problems in the care of carriers of acute porphyria: the choice of safe drugs for pharmacotherapy and the strategy to apply when potentially unsafe drugs cannot be avoided. METHODS AND RESULTS: A technique is presented for prediction of risk that a certain drug may activate the disease in a gene carrier for acute porphyria. It is based on a model explaining the clinical manifestations as a result of the acute overloading of a deficient enzyme within the hepatic heme biosynthetic chain. The capacity of the drug for induction of the rate-limiting enzyme in heme biosynthesis, e.g. housekeeping 5-aminolevulinate synthase (ALAS1), is assessed by critical appraisal of reports of the outcomes of clinical use of the drug, and by theoretical criteria. The assessment occurs within the frame of a flow-scheme employing variables of increasing specificity, i.e. endocrine properties of the drug, structure and metabolism pointing to affinity to cytochrome P450, hepatic load in therapeutic use, recognized affinity to major CYP species, capacity for CYP-induction or irreversible inhibition, and capacity to activate or modulate the transduction mechanisms of nuclear receptors affecting ALAS1-gene transcription. It is proposed that in the absence of a safer alternative, an urgently needed drug not should be withheld on the grounds of potential porphyrogenicity. After risk-benefit analysis it should be prescribed, but individualized preventive measures adapted to patient vulnerability may be needed. CONCLUSIONS: About 1000 therapeutic drugs categorized with regard to porphyrogenicity by the technique proposed are presented on the internet (http://www.drugs-porphyria.org).