IV. ANGIOTENSIN CONVERTING ENZYME INHIBITORS
The angiotensin converting enzyme (ACE) inhibitors are effective
antihypertensive agents and have other indications as well. The 2 avail-
able drugs in this group are very similar in their effects and may be
discussed together. The major difference between them is that captopril
is an active drug with a shorter duration of action 8-12 hours) while
enalapril is a prodrug that must be metabolized to the active form,
enalaprilat, which has a longer duration of action (12-24 hours).
* Inhibition of angiotensin converting enzyme results in decreased cir-
culating levels of angiotensin II as well as increased levels of
bradykinin, a vasodilator polypeptide.
* Chronic hypertension.
* Captopril is also labeled for the treatment of congestive heart fail-
ure that is unresponsive to digitalis and diuretics (see Chapter 4).
(PgDn for more text)
Contraindications and Warnings:
* Blood dyscrasias (Warning) have resulted from the use of ACE in-
hibitors, see adverse reactions.
* Renal impairment (Warning): These drugs interfere with the action of
the renin-angiotensin-aldosterone system and may contribute to a hyper-
kalemic state. These drugs should not be given to patients taking potas-
sium supplements or potassium-sparing diuretics.
* Hematologic: Reversible neutropenia or thrombocytopenia. The effect is
more common in patients with elevated BUN or other evidence of impaired
renal function (for captopril, 1 case in 500 patients with creatinine
above 1.6 mg/dL versus 1 in 8600 patients with normal serum creatinine).
* Renal: increased levels of serum creatinine and BUN and, rarely, acute
renal failure may occur, especially in patients with bilateral renal
* Electrolyte: elevated serum potassium occurs in about 1% of patients,
probably as a result of reduced aldosterone levels.
* Dysgeusia, an aberration of taste, has been reported in about 2-4% of
patients, a higher rate than for most drugs.
* Rash, with or without pruritis, has been reported in 4-7% of patients
taking captopril and somewhat less commonly in patients on enalapril.
(PgDn for more text)
* Nonspecific neurologic and gastrointestinal symptoms occur in 1-3% of
patients on either drug.
Hypotension is the major manifestation of serious
overdosage. Symptomatic management is usually sufficient (see Chapter
24) but both captopril and enalapril may be removed by hemodialysis if
* Other hypotensive agents: predictable additive hypotensive interac-
tions, especially in diuretic-induced hypovolemia.
* Potassium-sparing diuretics: predictable hyperkalemia occurs.
* Aspirin and NSAIDs may interfere with the hypotensive action of these
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