Pathophysiology
Clinical meaning
The clinician must recognize and manage additive hypotension resulting from concurrent use of multiple blood pressure-lowering agents, including intentional antihypertensives and medications with hypotensive side effects. Drug classes with hypotensive potential include: antihypertensives (ACEIs, ARBs, beta-blockers, calcium channel blockers, diuretics, alpha-blockers), psychiatric medications (antipsychotics -- particularly quetiapine and chlorpromazine via alpha-1 blockade; TCAs via alpha-1 blockade and direct myocardial depression; MAOIs via sympatholytic effects), opioids (histamine release and central sympatholytic effects), PDE5 inhibitors (sildenafil, tadalafil -- absolutely contraindicated with nitrates due to profound vasodilation), nitrates, and parkinsonism medications (levodopa/carbidopa, dopamine agonists). The clinician performs medication reconciliation identifying all potential contributors, assesses orthostatic vital signs (positive if systolic drop greater than or equal to 20 mmHg or diastolic drop greater than or equal to 10 mmHg within 3 minutes of standing), evaluates for end-organ hypoperfusion (syncope, dizziness, falls, acute kidney injury, myocardial ischemia), and implements risk mitigation strategies (staggering medication timing, dose reduction of least essential agents, avoiding concurrent prescribing of multiple hypotensive agents when possible).