Terazosin Alpha blockers

The client receiving the alpha blocker terazosin (Hytrin) who is complaining of a headache. 

The answer is b. (tlardman, p 229. Katzung, p 168.) Terazosin blocks a receptors in arterioles and venules It is 0 -selective. Perhaps this selectivity permits NE to exert unopposed negative feedback on its own release because of little or no effect on presynaptic a.2 receptors. Alpha blockers reduce arterial pressure in both resistance and capacitance vessels andT thereforet are quite effective in reducing blood pressure when a patient is in the upright position... 

Terazosin is an alpha-adrenoreceptor blocker that causes vasodilation and is used in the management of hypertension and benign prostatic hypertrophy. Beta-blockers and alpha-blockers can interact to induce hypotension since both act to reduce the blood pressure. Patients already on beta-blockers and who are started on alpha-blockers such as terazosin should be advised to take the terazosin dose at night to reduce the implications (falls) of first-dose hypotension. 

Geriatric Considerations - Summary Alpha-adrenergic blockers are modestly effective alone, and in combination with 5-alpha reductase inhibitors (e,g, finasteride) in the treatment of urinary obstructive symptoms related to benign prostatic hyperplasia. Alfuzosin is a "uroselective" alpha-blockerwhich appears to cause less orthostatic hypotension than nonselective alpha-blockers such as terazosin, prazosin, and doxazosin. 

Sotalol (Betapace) Timolol (Blocadren) Alpha blockers Doxazosin (Cardura) Phenoxybenzamine (Dibenzyline) Prazosin (Minipress) Terazosin (Hytrin) Trimethaphan (Arfonad)... 

The characteristics of individual alpha blockers are discussed in Chapter 20. Basically, these drugs can be differentiated according to their relative alpha-1 selectivity, their duration of action, and other pharmacokinetic properties. Prazosin (Minipress) has been the primary alpha blocker used in the past, but newer agents such as doxazosin and terazosin (Hytrin) are gaining acceptance in treating hypertension. Prazosin and other alpha blockers approved as antihypertensives are listed in Table 21-4. 

ALPHA-BLOCKERS BETA-BLOCKERS t efficacy of alpha-blockers t risk of first-dose 1 BP when alfuzosin, prazosin or terazosin is started in patients already taking beta-blockers Additive hypotensive effect may be used therapeutically Monitor BP at least weekly until stable. Warn patients to report symptoms of hypotension (lightheadedness, dizziness on standing, etc.). Watch for first-dose 1 BP... 

Indoramin is a postsynaptic selective alphai-adrenoceptor antagonist that is chemically distinct from the quinazo-lines. Unlike some other alpha-blockers, indoramin lowers blood pressure without a resulting reflex tachycardia or postural hypotension (1). However, it has largely been supplanted by more modern drugs, such as doxazosin, prazosin, and terazosin. 

Clinically important, potentially hazardous interactions with alpha blockers (alfuzosin), doxazosin, erythromycin, fosamprenavir, indinavir, itraconazole, ketoconazole, nitrates, ritonavir, tamsulosin, terazosin... 

The newer selective alphaj-adrenoreceptor-blocking agents, such as trimazosin, doxasozin, and terazosin, display a pharmacologic profile virtually identical to that of prazosin, but pharmacokinetic differences between the various alpha,-blockers exist. 

CALCIUM CHANNEL BLOCKERS ALPHA-BLOCKERS t efficacy of alpha-blockers t risk of first-dose 4. BP with alfuzosin, prazosin and terazosin Additive hypotensive effect may be used therapeutically Watch for first-dose i BP when starting either drug when the patient is already established on the other consider reducing the dose of the established drug and starting the new agent at the lowest dose and titrating up... 

Severe first-dose hypotension, and synergistic hypotensive effects that occurred when a patient taking enalapril was given bnna-zosin have been replicated in healthy subjects. The first-dose effect seen with other alpha blockers (particularly alfuzosin, prazosin and terazosin) is also likely to be potentiated by ACE inhibitors. In one small study tamsulosin did not have any clinically relevant effects on blood pressure that was already well controlled by enalapril. 

Direct information is limited. Acute hypotension (dizziness, fainting) sometimes occurs unpredictably with the first dose of some alpha blockers (particularly, alfuzosin, prazosin and terazosin but see Alpha blockers , (p.83)), and this can be exaggerated if the patient takes or is already taking a beta blocker or a calcium-channel blocker (see Alpha blockers + Beta blockers , below, and Alpha blockers + Calcium-channel blockers , p.85). It would therefore seem prudent to apply the same precautions to ACE inhibitors, namely reducing the dose of the ACE inhibitor to a maintenance level if possible, then starting the alpha blocker at the lowest dose, with the first dose given at bedtime. Note that the acute hypotensive reaction appears to be short-lived. There is limited evidence that terazosin and tamsulosin may not cause an additional hypotensive effect in the longer term in patients with BPH who have hypertension already well-controlled with ACE inhibitors. Nevertheless, caution should be exercised in this situation, and a dose reduction of the ACE inhibitor may be required. 

Blood pressure may fall sharply when calcium-channel blockers are first given to patients already taking alpha blockers (particularly prazosin and terazosin), and vice versa. In a small study, tamsulosin did not have any clinically relevant effects on blood pressure well controlled by nifedipine. Verapamil may increase the AUC of prazosin and terazosin. Alpha blockers and calcium-channel blockers may be combined for additional blood pressure lowering in patients with hypertension. 

A study in 24 subjects given dutasteride 500 micrograms daily for 14 days found that when tamsuiosin 400 micrograms or terazosin (titrated to 10 mg) were also given once daily for 14 days, the pharmacokinetics of the alpha blockers remained unchanged. Furthermore, a clinical study in 327 men demonstrated that the combination of tamsuiosin and dutasteride was well-tolerated over a period of 6 months. ... 

Alpha-adrenoceptor antagonists. Prazosin, afluzosin, indoramin, terazosin and doxazosin are all a-adrenoceptor blockers, with selectivity for the a -subtype. They cause significant increases (compared to placebo) in objective measures such as maximal... 

Alpha-Adrenergic Blockers Phentolamine (Regitine) selective Doxazosin mesylate (Cardura), terazosin HC1 (Hytrin)... 

A recent study by Bach, Schmitt, and Ebeling compared three prescriptive medications with a standardized saw palmetto extract. The drugs worked by two different mechanisms. Finasteride is a synthetic 5-alpha-reductase inhibitor, and the other two drugs, terazosin and alfuzosin, are alpha-1 blockers. In all important parameters, the saw palmetto was a comparable treatment with far fewer side effects. It decreased residual urine volume, reduced irritation, and increased urinary flow 80 percent of patients rated their improved quality of life as good to very good. 

Alpha -selective blocker prototype used in HTN and benign prostatic hyperplasia. Tox first-dose orthostatic hypotension. Other osins terazosin, doxazosin. 

Alpha-adrenergic blockers phentolamine (Regitine) doxazosin mesylate (Cardura), terazosin HCl (H) n). 

---