Benadryl and fosinopril belong to the same ACEI class of antihypertensive drugs, concomitant use may increase renal impairment and other adverse effects, concomitant use is not recommended. Benazepril and fosinopril are both ACEI antihypertensive drugs, which can lower blood pressure by inhibiting the production of angiotensin 2, preventing its further vasoconstriction and promoting the release of aldosterone; the two have the same mechanism of action and are not complementary. If the two drugs are used together, it may increase the risk of adverse reactions, such as cough, hypotension, hyperkalemia, renal impairment. Both drugs are contraindicated in people with a history of allergy to ACEIs, pregnant and breastfeeding women, and the combination with aliskiren is also prohibited in diabetic patients. In conclusion, Benadryl and Fosinopril are not recommended to be taken together. In the combination drug regimen for hypertension, ACEIs can be combined with dihydropyridine calcium channel antagonists such as amlodipine and diuretics such as hydrochlorothiazide. The above medications should be used under medical supervision.