Antihypertensive drugs - adverse effects in the elderly

Antihypertensive therapy in the elderly is more complex than in younger patients because increasing age is associated with degeneration of organ systems, existence of multiple disease states and consequently multiple drug therapy. These considerations may lead to altered pharmacokinetic and pharmacodynamic profi les of drugs and may make the choice of antihypertensive regimen difficult. No antihypertensive is risk-free or universally effective, therefore therapy should be individualised , taking into consideration the associated risks and benefits.

Diuretics have been commonly associated with adverse effects in the elderly , including hyponatraemia and hyper- or hypocalaemia. Asymptomatic electrolyte disturbances can occur. Diuretics have the potential to interact with many other drugs.

Beta blockers reduce cardiac output , heart rate and renal blood flow and increase peripheral resistance, possibly predisposing the elderly patient to congestive heart failure . Beta blockers should be avoided in patients with reduced renal function and reduced cardiac output . However, drugs with intrinsic sympathomimetic activity do not decrease cardiac output and may be used. Beta blockers also mask symptoms of hypoglycaemia. Central nervous system adverse effects include insomnia, fatigue , cognitive loss, anorexia, feelings of sadness and helplessness, depression , nightmares and hallucinations.

Prazosin has been associated with an increasec incidence of orthostasis , occasional tachycardia and first dose syncope in the elderly . After the initial dose, prazosin can cause a marked postural fall in blood pressure , which adversely effects renal and cerebral perfusion , leading to dizziness ,d falls. To minimise this problem patients should ; advised to take a small initial dose at bedtime

and to remain supine for at least 3 hours. Patients with renal failure may experience confusion , visual hallucinations, paranoid ideas, drowsiness and inhibited behaviour. Prazosin therapy may cause diarrhoea. Tolerance to therapy may develop with long term use.

The centrally acting alpha agonists tend to preserve renal and cerebral blood flow . Methyldopa is associated with significant orthostatic hypotension, dry mouth , depression, drowsiness , lethargy and sedation . It may sometimes reduce cardiac output and , for this reason , is not used in patients with congestive heart failure . Clonidine may cause a severe rebound in blood pressure if the drug is discontinued abruptly , especially after high dose, long term therapy or with concomitant beta blockers ; therefore it is not the drug of choice in non-compliant patients .

The angiotensin-converting enzyme inhibitors ~,e particularly effective in elderly hypertensives, the most common adverse effect being cough , which usually resolves with time. ACE inhibitors have a large number of potential interactions with other drugs including digoxin , morphine, lithium, NSAIDs, diuretics, vasodilators and prazosin .

Calcium channel blockers tend to achieve greater blood pressure reduction in elderly patients than in younger patients, necessitating lower dosages. Variable actions on the myocardium, heart rate , ventricular filling pressure and cardiac index may lead to problems in some patients . There is no significant effect on plasma insulin , therefore these drugs may be preferred in patients with hypertension and diabetes.

In elderly patients " , , antihypertensive therapy should proceed according to an individualized risk : benefit approach',

Lamy PP Potential adverse effects of antlhypenenSlve drugs In the elderly Journal of Hypertension 6 (Suppl 1) 81 -85. Nov 1988 [39 re ferences 1 ....