Pilot Experiments on the Actions of Drugs Injectedinto
Br. J. Pharmac. (1986), 87, 495-500 Pilot experiments on the actions ofdrugs injected into the human corpus cavernosum penis G.S. Brindley Department ofPhysiology, Institute of Psychiatry De Crespigny Park, London SE5 8AF 1 Seven drugs that are known to relax smooth muscle (phenoxybenzamine, phentolamine, thymoxamine, imipramine, verapamil, papaverine, naftidrofuryl) caused erection when injected intracavernosally. 2 Salbutamol, hydralazine, lignocaine and bupivacaine caused tumidity but not erection. 3 Metaraminol and guanethidine caused shrinkage followed by tumidity. 4 Neostigmine, atropine, propranolol and idazoxan had no effect in the doses tried. 5 It is argued that the seven drugs that cause erection do so by relaxing vascular and trabecular smooth muscle within the cavernosal space, and that the two that cause shrinkage ofthe penis do so by constricting vascular and trabecular smooth muscle within the cavernosal space. 6 It is argued that muscarinic and P-adrenergic transmission play no important part in erectile mechanisms within the corpora cavernosa. 7 Papaverine, phenoxybenzamine and metaraminol, given intracavernosally, are already used therapeutically. Uses are suggested for thymoxamine, phentolamine, verapamil and guanethidine. Introduction Papaverine (Virag, 1982) and phenoxybenzamine and the left corpus cavernosum was squeezed in the same phentolamine (Brindley, 1983a; 1983b) cause erection way; then the penis was firmly pinched transversely at when given by intracavernosal injection. least six different places along it length in succession. Metaraminol, given by the same route, shrinks the These three actions were then repeated. penis (Brindley, 1984a). These drugs are now in The drugs were injected in a volume of 2 ml or less, therapeutic use (Virag, 1982; Virag et al., 1984; except for phenoxybenzamine, hydralazine and naf- Brindley, 1983b; 1984a,b; 1986; Zorgniotti & Lefleur, tidrofuryl, which were diluted with 10 ml of 0.9% 1985).
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