His elderly wife reports that he often seems very confused at night and on a couple of occasions he has had episodes of nocturnal wandering and getting lost in the house. He says that each morning he finds he has urinated on the floor during the night, although he has no recollection of this. Tiller, Department of Psychiatry, University of Melbourne, Royal Melbourne Hospital, MelbourneĪ 78 year old man who has had a longstanding sleep disorder presents for a review. If postural hypotension (a blood pressure fall of >20 mm Hg systolic, >10 mm Hg diastolic) is detected, alternative drug treatment may be indicated, especially in the elderly and in patients with cerebrovascular disease. terazosin) may be an advantage.Īll patients taking prazosin should have lying and standing blood pressures checked regularly. The once daily dose regimen of the newer alpha 1 blockers (e.g. Tolerance (loss of antihypertensive effect with prolonged use) does not occur with prazosin, although many patients need a dose of 20 mg/day in divided doses for maximal effect. As with most antihypertensive drugs, there are marked variations in blood pressure response between patients. It is therefore safe to stop prazosin abruptly in mild hypertension. There is no evidence that rebound hypertension occurs after sudden withdrawal of prazosin (unlike methyldopa and clonidine). Prazosin should be used with care in this patient group, although it may be preferred for men with symptoms of benign prostatic hypertrophy (improving hesitancy). Normal elderly people have impaired baroreceptor reflexes and have an increased tendency to orthostatic hypotension which is exacerbated by alpha blocking drugs, even with repeated use. Postural hypotension can be incapacitating, but is usually self limiting: patients with cerebrovascular disease may be at increased risk. Postural hypotension is particularly likely to occur when the dose is increased, or when additional drugs (especially beta blockers) are added to the regimen. The normal reflex tachycardia and small rise in diastolic blood pressure on standing is suppressed with these drugs, possibly because alpha2 (presynaptic) inhibition of catecholamine release is not blocked. With chronic use, postural hypotension may persist. With prazosin and other alpha1 (postsynaptic) adrenergic blockers, first dose hypotension due to arterial and venous dilatation is well recognised and is minimised by using a low starting dose. Be prepared to consider the diagnosis on the basis of history alone. Remember that postural hypotension may not be present when you examine the patient. Symptomatic postural hypotension may occur at levels of blood pressure considered normal in young adults, if hypertensive vascular damage is present. Postural hypotension is usually defined as a blood pressure fall on standing (which may need to be prolonged) of >20 mm Hg systolic, >10 mm Hg diastolic. Blood pressure was 150/90 lying and standing on no therapy. The prazosin was stopped and one week later her symptoms had improved and the bruising had resolved. Standing reproduced her light-headedness, which was relieved by sitting down. The heart rate was 76/minute both lying and standing. On examination, sitting blood pressure was 140/78, falling to 115/65 on standing. She had been taking prazosin, 2 mg 3 times daily, for the previous 7 months and no other medication. Her last episode had been severe enough to cause her to fall, striking her head and arm. She told us that for some time she had been suffering from intermittent light-headedness while standing, which she had not reported. We noticed that she had severe bruising on the right side of her face and right forearm. Marley, Senior Lecturer, Department of Community Medicine, University of Adelaide, AdelaideĪ 76 year old lady with hypertension attended for a regular review of her blood pressure which had been well controlled. Taverner, Senior Lecturer, Department of Clinical and Experimental Pharmacology, and J.
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