A girl on sulphonamides developed abdominal pain and presented to emergency with seizure. What is the probable diagnosis?
Correct Answer: Acute intermittent porphyria
Description: Abdominal pain is the most common symptom in Acute intermittent porphyria and is usually steady and poorly localized but may be cramping. Seizures can be due to neurologic effects or to hyponatremia. Treatment of seizures is difficult because most anti seizure drugs can exacerbate AIP (clonazepam may be safer than phenytoin or barbiturates). The drugs which precipitate attacks of acute intermittent porphyria are microsomal enzyme inducers. They are metabolized by p450 enzyme. In response to these drugs the synthesis of cytochrome p450 proteins increases, leading to an enhanced consumption of heme, a component of p450 proteins. This in turn causes a decrease in the concentration of heme in the liver. Since the patient is deficient in enzymes synthesizing porphyrins it cannot makeup for the increase in demand of porphyrins. This leads to increased accumulation of porphyrin precursors precipitating attacks of porphyria. Some impoant drugs causing acute intermittent porphyria :- Barbiturate Chloramphenicol Sulfonamides Thiopental Na Oral contraceptives Phenylbutazone Rifampicin Ref: Desnick R.J., Balwani M. (2012). Chapter 358. The Porphyrias. In D.L. Longo, A.S. Fauci, D.L. Kasper, S.L. Hauser, J.L. Jameson, J. Loscalzo (Eds), Harrison's Principles of Internal Medicine, 18e.
Category:
Pharmacology
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