Antihypertensive Drugs

The aging vasculature undergoes progressive structural changes that reduce aortic compliance. Elastin fibers fragment and are replaced by stiffer collagen; advanced glycation end products cross-link collagen molecules; medial calcification adds further rigidity; and endothelial dysfunction reduces nitric oxide-mediated vasodilation. Under normal conditions, the compliant aorta expands during systole to absorb part of the stroke volume (the Windkessel effect) and recoils during diastole to maintain diastolic pressure and coronary perfusion. In the stiff aging aorta, this buffering is lost: systolic blood pressure rises markedly because the pressure wave is no longer damped, and diastolic blood pressure falls because elastic recoil is absent. The result is isolated systolic hypertension — systolic at or above 140 with diastolic below 90 millimeters of mercury — the dominant pattern in patients over 60 years.

Pulse pressure (systolic minus diastolic) exceeding 60 to 70 millimeters of mercury predicts particularly high cardiovascular event rates. Systolic blood pressure is a more powerful predictor of cardiovascular risk than diastolic blood pressure in patients over 50 to 55 years old. The therapeutic goal is to lower systolic blood pressure while avoiding a disproportionate fall in diastolic — reducing diastolic below 65 to 70 millimeters of mercury in patients with established coronary artery disease risks impairing coronary perfusion (the J-curve phenomenon).

The SHEP trial (Systolic Hypertension in the Elderly Program, 1991) enrolled 4,736 patients aged 60 or above with isolated systolic hypertension and randomized them to chlorthalidone-based therapy versus placebo. Active treatment produced a 36 percent reduction in stroke, 32 percent reduction in major cardiovascular events, 54 percent reduction in heart failure, and 27 percent reduction in coronary events — establishing that treating isolated systolic hypertension in the elderly provides substantial cardiovascular protection and confirming chlorthalidone as a cornerstone agent.

The Syst-Eur trial (1997) enrolled 4,695 patients aged 60 or above with isolated systolic hypertension and randomized them to nitrendipine (a dihydropyridine calcium channel blocker) versus placebo, producing a 42 percent reduction in stroke and 31 percent reduction in all cardiovascular events — establishing dihydropyridine calcium channel blockers as equally effective first-line agents for elderly isolated systolic hypertension.

The HYVET trial (Hypertension in the Very Elderly, 2008) enrolled 3,845 patients aged 80 or above (mean age 83.6 years) and randomized them to indapamide with or without perindopril versus placebo. Active treatment produced a 30 percent reduction in stroke, a 21 percent reduction in all-cause mortality, and a 64 percent reduction in heart failure — with the critical finding that the treatment group had fewer serious adverse events than placebo, demonstrating that antihypertensive treatment in the very elderly is safe. HYVET established the evidence base for treating patients aged 80 or above, with indapamide plus perindopril as the evidence-based regimen.

The SPRINT elderly subgroup (2,636 patients aged 75 or above) showed that intensive systolic blood pressure control below 120 millimeters of mercury by automated unattended measurement reduced composite cardiovascular events by 34 percent and all-cause mortality by 33 percent in non-frail elderly patients — at the cost of higher rates of acute kidney injury, syncope, and electrolyte disturbances. Note that SPRINT's automated unattended measurement yields readings approximately 5 to 10 millimeters of mercury lower than standard clinical measurement, so the 120 millimeters of mercury target corresponds to approximately 130 millimeters of mercury by standard measurement.

Orthostatic hypotension is defined as a fall in systolic blood pressure of at or above 20 millimeters of mercury or diastolic blood pressure of at or above 10 millimeters of mercury within 3 minutes of standing from a supine or seated position. Its prevalence is approximately 20 percent of community-dwelling elderly patients, rising above 50 percent in institutionalized elderly, and is associated with approximately twice the risk of falls, syncope, and cardiovascular events. All antihypertensives can worsen orthostatic hypotension — alpha-1 blockers, loop diuretics, and calcium channel blockers are most problematic.

Blood pressure must be checked in both sitting and standing positions at every visit in elderly hypertensive patients. Management includes review and simplification of the antihypertensive regimen, optimization of dose timing (avoid diuretics in the evening), ensuring adequate hydration, compression stockings, advice on slow positional changes, and avoidance of alcohol. Cognitively neutral agents with least orthostatic effect — amlodipine, chlorthalidone, angiotensin receptor blockers — should be preferred.

Glomerular filtration rate declines approximately 1 mL/min per year after age 40. Renally excreted drugs accumulate — atenolol, lisinopril, and low-molecular-weight heparins require dose reduction. Serum creatinine alone overestimates renal function in the elderly because reduced muscle mass lowers creatinine production — the CKD-EPI equation should be used. Reduced hepatic blood flow and first-pass metabolism increase the bioavailability of hepatically metabolized agents including labetalol, metoprolol, propranolol, and nifedipine. Lipophilic drugs have larger volumes of distribution and longer effective half-lives in the elderly due to increased body fat relative to lean mass. Reduced plasma albumin increases the free fraction of highly protein-bound drugs. Lipophilic drugs cross the blood-brain barrier more readily in aging, increasing central nervous system sensitivity to sedating effects of clonidine, methyldopa, and lipophilic beta-blockers.

In elderly patients — particularly those who are frail or have multiple comorbidities — a conservative initiation strategy is essential. Begin at half the standard starting dose when possible: chlorthalidone 6.25 mg, amlodipine 2.5 mg, perindopril 2 mg. Titrate slowly every 4 to 6 weeks rather than every 2 to 4 weeks, and add second agents only after confirming tolerance and stability of the first. The complete medication list should be reviewed at every visit — the average elderly hypertensive patient takes 5 to 7 prescription medications, and drug-drug interactions are a major source of adverse effects including additive hypotension, acute kidney injury, and hyperkalemia. Nonsteroidal anti-inflammatory drugs, frequently taken for musculoskeletal pain, antagonize both diuretics and renin-angiotensin-aldosterone system inhibitors and must be specifically identified at every medication review.

In frail elderly patients experiencing falls, orthostatic hypotension, or declining quality of life attributable to antihypertensive therapy, withdrawal or dose reduction (de-prescribing) should be actively considered rather than reflexively avoided. The benefit-risk calculation for intensive blood pressure lowering shifts unfavorably as frailty advances — quality of life and functional status become primary goals.