Letters to the EditorPeripheral, Pruritic, and Purpuric Eruptions Due to Prazosin Kader N. MohammedMD Kader N. Mohammed Search for more papers by this author Published Online:1 Jan 1995https://doi.org/10.5144/0256-4947.1995.81SectionsPDF ToolsAdd to favoritesDownload citationTrack citations ShareShare onFacebookTwitterLinked InRedditEmail AboutIntroductionTo the Editor: Prazosin is a selective α1 receptor blocker frequently used in the treatment of hypertension. The major side effect of this drug is the “first dose phenomenon” characterized by severe postural hypotension and reflex tachycardia which occur following the initial dose. Although urticaria and angioedema have been described,1 allergic reactions to prazosin are rare. We describe a patient who developed intense pruritis followed by purpuric rash over the legs which spread upwards to involve the lower limbs up to the waist. To the best of our knowledge, purpuric rashes due to prazosin have not been reported.A 70-year-old male presented with extensive erythematous rash of the lower limbs for the past 10 days. He was on prazosin 0.5 mg b.i.d. and experienced itchiness of both legs on the seventh day of treatment followed by a rash. He had no fever or bleeding disorder. Previous treatment included metoprolol, nifedipine and indapamide without any adverse effects. On examination, his blood pressure was 180/100 mm/Hg standing, 170/100 mg/Hg recumbent and almost equal in both arms. The erythematous rash was maculopapular, not blanching on pressure, scattered and extending to the gluteal region. There were excoriations all over the limbs but were most prominent over the buttocks. The other parts of the body were relatively free. Full blood picture including platelet count was within normal limits. The patient was advised to stop taking prazosin and after three weeks the rash disappeared, leaving mild hyper-pigmentation.The minor adverse effects of prazosin include dizziness, headache, nausea and lethargy.2 These are common due to the pharmacologic action of the drug and usually diminish with the continuation of therapy or reduction in dosage. Drugs which cause purpura are arsenic, bismuth, barbiturates, carbromal, ethyl stilbesterol, phenacetin, sulphonamide, food additives such as tartarazine and tolbutamide, etc.3 Carbromal, a sedative, produces a well-recognized and unique pattern of purpura. Drugs can cause vascular or non-thrombocytopenic purpura. The vessel damage may be due to either the direct toxic effect of the drug or the hypersensitivity reaction occurring at the surface of endothelial cells, adjacent tissues or mediated through immune complexes.3 A good history is often helpful in the diagnosis of drug-induced purpura, which usually resolves upon withdrawal of the offending drug. Nonspecific rashes due to prazosin are seen but purpuric eruptions are rare. Since prazosin is commonly administered, it is useful to look for purpura when patients present with drug rash, especially when it involves the lower limbs.ARTICLE REFERENCES:1. Ruzicka T, Ring J. "Hypersensitivity to prazosin" . Lancet. 1983; 1:473-4. Google Scholar2. Hoffman BB, Lefkowitz RJ. "Adrenergic receptor antagonists" . Goodman and Gillman’s ‘The Pharmacological Basis of Therapeutics’. In: Gilman AG, Rall TW, Nies AS, Taylor P. 8th ed.McGraw-Hill Inc, New York, 1991;221-43. Google Scholar3. Millikan LE. "Drug eruptions" . Dermatology. In: Moschella SL, Hurley HJ. 3rd ed.W. B. Saunders Company, Philadelphia, PA, USA, 1992;535-73. Google Scholar Previous article Next article FiguresReferencesRelatedDetails Volume 15, Issue 1January-February 1995 Metrics History Published online1 January 1995 InformationCopyright © 1995, Annals of Saudi MedicineThis work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.PDF download