An estimated 30% of adults in the United States have hypertension; thus, antihypertensives are medications commonly found in patient homes.1 Several classes of drugs used to treat hypertension are discussed in this chapter: diuretics, sympatholytic agents, angiotensin-converting enzyme inhibitors (ACEIs), angiotensin II receptor blockers (ARBs), and vasodilators (Table 196-1). Calcium channel blockers and β-blockers, also used in the treatment of hypertension, are discussed elsewhere (see chapters 195, "Calcium Channel Blockers," and 194, "Beta-Blockers").
TABLE 196-1Summary of Antihypertensive Drugs ||Download (.pdf) TABLE 196-1 Summary of Antihypertensive Drugs
|Class ||Drug ||Mechanism of Action ||Clinical Presentation with Toxicity ||Comments |
|Diuretics ||Acetazolamide ||Inhibition of proximal tubule sodium-hydrogen exchange || |
Non–anion gap metabolic acidosis
|Inhibition of distal tubule sodium chloride absorption || |
|Metabolic complications, such as hypokalemia, glucose intolerance, and hyperuricemia seen with increased therapeutic thiazide doses. |
|Inhibition of sodium-potassium-chloride symporter in renal loop of Henle || |
|Inhibition of sodium absorption and potassium elimination in renal distal collecting duct || |
|Mineralocorticoid antagonist || |
|Sympatholytics || |
|α1-Adrenergic receptor antagonist ||Hypotension ||Phenylephrine may be used for refractory hypotension. |
α2-Adrenergic receptor agonist
Imidazoline receptor agonist
μ-Receptor opioid agonist
Dopamine considered agent of choice for hypotension.
Phenylephrine may be used for refractory hypotension.
|Imidazoline receptor agonist ||Hypotension, Bradycardia, and Neurologic depression || |
|Decreased norepinephrine release || |
Hemolytic anemia (idiosyncratic reaction to methyldopa)
|ACE inhibitors || |
Inhibition of ACE
Inhibition of bradykininase
Epinephrine, corticosteroids, and antihistamines have no proven benefit in ACEI-induced angioedema.
Icatibant 30 milligrams SC or C1 esterase inhibitor [human] 1000 U IV are effective in ACEI-induced angioedema.
|Angiotensin receptor blockers || |
|Angiotensin II receptor antagonist || |
Angioedema (less common than with ACE inhibitors)
|Epinephrine, corticosteroids, or antihistamines have no proven benefit in ARB-induced angioedema. |
|Vasodilators ||Hydralazine ||Arteriolar vasodilation || |
Lupus-like syndrome (idiosyncratic reaction to hydralazine)
| ||Minoxidil ||Arteriolar vasodilation || |
Increased myocardial oxygen demand
| ||Sodium nitroprusside ||Arteriolar and venous vasodilation (via nitric oxide release) || |
Thiocyanate toxicity (after prolonged infusion)
Cyanide toxicity (very rare)
Thiosulfate should be administered if cyanide toxicity is considered.
Many pharmacies mix sodium nitroprusside and thiosulfate to avert cyanide toxicity.
For most of these agents, life-threatening toxicity is not expected in acute overdose.2 In nearly all cases, good supportive care is adequate. The initial approach to the patient with potential overdose of an antihypertensive drug is fairly uniform. Secure the airway as necessary, establish IV access, provide continuous cardiac monitoring, and obtain an ECG. A bolus of crystalloid solution is first-line treatment for hypotension. If a vasopressor is required, a direct-acting drug such ...