Nursing care
ACE Inhibitors: what to check before you give it
Written and reviewed by Dana Whitfield, RN, MSN · 4 min read · Updated September 2026
Short answer
ACE inhibitors block the conversion of angiotensin I to angiotensin II, lowering blood pressure and reducing cardiac afterload. Check baseline potassium, renal function, and blood pressure before the first dose. The dry cough is harmless and usually prompts a switch to an ARB; angioedema is the reaction that stops the drug for good.
Why this drug and not another
ACE inhibitors such as lisinopril and enalapril are first-line for hypertension, heart failure with reduced ejection fraction, and diabetic nephropathy because they reduce afterload and slow the progression of proteinuria. They are often chosen over other antihypertensives when a patient has coexisting diabetes or chronic kidney disease, since the renoprotective effect is part of the drug class itself, not a side benefit.
Prescribers also reach for an ACE inhibitor post-myocardial infarction, where reducing ventricular remodelling improves long-term outcomes. Knowing the indication matters because it changes your monitoring priorities: a diabetic patient on lisinopril needs closer renal and potassium surveillance than someone taking it for uncomplicated hypertension.
Administration and timing
Give the first dose with the patient supine or seated, and check blood pressure before and roughly one hour after, since first-dose hypotension is well documented, particularly in patients who are volume-depleted or already on a diuretic. Lisinopril is dosed once daily and does not require food. Enalapril may be given once or twice daily depending on the formulation and indication.
Hold the dose and notify the prescriber if systolic blood pressure is below the parameters set for that patient, commonly under 90-100 mmHg, or if potassium is already elevated. Do not double a missed dose. If the patient is due for surgery, ACE inhibitors are frequently held the morning of the procedure because of the same hypotension risk under anaesthesia — confirm the facility's protocol rather than assuming.
Monitoring parameters
Check serum creatinine and potassium before starting and again within one to two weeks of initiation or any dose increase. A small rise in creatinine, up to about 30 percent above baseline, is expected and not usually a reason to stop the drug; a larger rise suggests renal artery stenosis and needs prescriber review.
Monitor blood pressure at each visit and watch potassium closely if the patient is also on a potassium-sparing diuretic, a potassium supplement, or an NSAID. Track for a persistent dry cough, which is common and not dangerous, but distinguish it clearly from facial or laryngeal swelling, which is an emergency, not a nuisance.
Adverse effects to report
The dry, non-productive cough affects a meaningful minority of patients and is caused by bradykinin accumulation rather than an allergic process. It is uncomfortable but not harmful, and it is the standard reason prescribers switch the patient to an angiotensin receptor blocker, which does not carry the same cough risk.
Angioedema is different in kind, not just degree. Swelling of the lips, tongue, throat, or face can obstruct the airway and constitutes a medical emergency requiring immediate discontinuation of the drug and, if the airway is threatened, emergency management. Once a patient has had angioedema on an ACE inhibitor, that patient should never receive an ACE inhibitor again, and ARBs are used with caution given a small cross-reactivity risk.
Contraindications and cautions
ACE inhibitors are contraindicated in pregnancy at any stage, since they are associated with fetal renal damage, oligohydramnios, and skull ossification defects; confirm pregnancy status before starting therapy in anyone of childbearing potential. They are also contraindicated in patients with a history of ACE-inhibitor-induced angioedema and in bilateral renal artery stenosis.
Use caution in patients with hyperkalaemia, significant renal impairment, or hypovolaemia, and in those taking potassium-sparing diuretics, potassium supplements, or NSAIDs, all of which raise the risk of hyperkalaemia or reduced renal perfusion when combined with an ACE inhibitor.
Teaching points the exam tests
NCLEX questions on this class typically test whether you can distinguish the harmless cough from the dangerous angioedema, so be precise in your own head about which symptom triggers a switch and which triggers a permanent stop. Teach patients to report facial or throat swelling immediately and to seek emergency care rather than waiting for the next dose.
Teach patients to rise slowly from sitting or lying to avoid orthostatic hypotension, particularly after the first dose or a dose increase, and to avoid salt substitutes containing potassium chloride. Reinforce that missing doses does not require doubling up, and that this drug is not stopped abruptly without medical guidance, since abrupt withdrawal can cause rebound hypertension.
The next step on this is the same as on everything else here: answer questions and read the rationales. Our cardiovascular practice questions are the closest set to what this page covers.
Common questions
Is the ACE inhibitor cough dangerous?
No. It is a dry, persistent cough caused by bradykinin buildup, not an allergic reaction, and it resolves once the drug is stopped. It is uncomfortable enough that prescribers usually switch the patient to an ARB, but it is not an emergency.
What is the difference between the cough and angioedema?
The cough is a nuisance side effect of the drug's mechanism. Angioedema is swelling of the lips, tongue, throat, or face that can obstruct breathing, is a medical emergency, and means the patient can never take an ACE inhibitor again.
Why do ACE inhibitors cause a rise in creatinine?
They reduce efferent arteriolar constriction in the glomerulus, which lowers filtration pressure. A rise of up to about 30 percent from baseline is expected and monitored, not usually a reason to discontinue the drug.
Can ACE inhibitors be given in pregnancy?
No. They are contraindicated at every stage of pregnancy due to the risk of fetal renal damage and other malformations. Confirm pregnancy status before starting and switch to a pregnancy-safe alternative if pregnancy is suspected or confirmed.
Why is potassium checked so often on this drug?
ACE inhibitors reduce aldosterone secretion, which decreases potassium excretion and can lead to hyperkalaemia, especially when combined with potassium-sparing diuretics, potassium supplements, or NSAIDs.
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