It was withdrawn from market worldwide in 1988 because it caused QT interval prolongation and torsades de pointes, greatly increasing the risk of sudden death.[1][3] The cardiac side effects were not detected during clinical development, only becoming apparent after the drug was in wide use.[1]
Prenylamine has two primary molecular targets in humans: calmodulin and myosin light-chain kinase 2, found in skeletal and cardiac muscle.[4] Pharmacologically, it decreases sympathetic stimulation on cardiac muscle, predominantly through partial depletion of catecholamines via competitive inhibition of reuptake by storage granules,[clarification needed] leading to further depletion due to spontaneous leakage as a result of disturbance of equilibrium.[clarification needed][5] This depletion mechanism is similar to that of reserpine because both agents target the same site on the storage granule; however, prenylamine shows a high affinity for cardiac tissue, while reserpine is more selective toward brain tissue.[6]
Prenylamine slows cardiac metabolism via calcium transport delay by blockade of magnesium-dependent calcium transportATPase. It demonstrates beta blocker–like activity that results in reduction of heart rate but shows an opposing effect on tracheal tissue response.[clarification needed][5]
^Fung M, Thornton A, Mybeck K, Wu JH, Hornbuckle K, Muniz E (2001-01-01). "Evaluation of the Characteristics of Safety Withdrawal of Prescription Drugs from Worldwide Pharmaceutical Markets-1960 to 1999*". Drug Information Journal. 35 (1): 293–317. doi:10.1177/009286150103500134. ISSN2168-4790. S2CID73036562.
^Obianwu HO (1965-04-01). "The effect of prenylamine (segontin) on the amine levels of brain, heart and adrenal medulla in rats". Acta Pharmacologica et Toxicologica. 23 (4): 383–390. doi:10.1111/j.1600-0773.1965.tb00362.x. PMID5899695.