1. A. Although many drugs can evoke a reaction such as a rash, a rash and a dry cough are well-recognized side effects of angiotensin converting enzyme
(ACE) inhibitors, such as captopril. Up to 20% of these patients may develop a cough with ACE inhibitors. The cause is not known for certain, but it may be related to the accumulation in the lungs of bradykinin or other inflammatory mediators. Inhibiting ACE leads to an increase in bradykinin, which is normally broken down by this enzyme. The rash was originally attributed to a sulfhydryl group in captopril but is known to occur with other non-sulfhydryl-containing ACE-inhibitors.
2. C. The vasodilation caused by bradykinin, hista-mine, hydralazine, and acetylcholine depends in part upon nitric oxide release from the endothelium. Minoxidil activates K+ channels, which results in vascular smooth muscle hyperpolarization and thereby relaxation.
3. E. Guanethidine does not normally cause release of catecholamines from the adrenal medulla. However, it may provoke the release of cate-cholamines from pheochromocytoma. This action plus its ability to antagonize neuronal uptake of cat-echolamines could trigger a hypertensive crisis. The other drugs are good choices to lower blood pressure in a patient with pheochromocytoma: metyro-sine, by decreasing synthesis; labetalol, by blocking both the a- and p-effects of the catecholamines; prazosin and especially phenoxybenzamine, by introducing a fairly long a-blockade.
4. B. Clonidine is an antihypertensive because it decreases sympathetic outflow from the CNS to the periphery and therefore reduces the sympathetically induced stimulation of renin release. The sympathetic effect on renin release is mediated by preceptors, so prazosin, an a-blocker would not decrease release. Captopril is an ACE inhibitor and is likely to enhance renin release, although it would prevent the effects of renin by reducing the formation of angiotensin II. Nitroprusside and diazoxide are directly acting vasodilators and will promote renin release reflexively.
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