Benazepril

BRAND NAMES

Lotensin: This is the most common brand name for benazepril as a single-ingredient drug for human use.

Lotrel: This brand name is used for a combination of benazepril and the calcium channel blocker amlodipine.

Lotensin HCT: This is the brand name for a combination of benazepril and the diuretic hydrochlorothiazide (HCT). 

MECHANISM OF ACTION

Benazepril is a prodrug that is primarily converted into its active form, benazeprilat, in the liver. As an angiotensin-converting enzyme (ACE) inhibitor, benazeprilat works by blocking the enzyme responsible for converting angiotensin I into angiotensin II. This mechanism is key to its effectiveness in treating hypertension and heart failure.

PHARMACOKINETICS

Absorption

Benazepril is well absorbed from the gastrointestinal tract after oral administration, with an average bioavailability of about 37%. However, because it is a prodrug, benazepril itself is inactive until it is converted in the liver to its active form, benazeprilat. Food intake does not significantly affect the absorption of benazepril.

Distribution

The volume of distribution of benazepril’s active metabolite, benazeprilat, is approximately 0.3 L/kg in humans. This indicates that benazeprilat distributes moderately into body tissues beyond the bloodstream.

Metabolism

Benazepril is primarily metabolized in the liver, where it is converted into its active form, benazeprilat. This conversion occurs through enzymatic hydrolysis. Benazeprilat is the active metabolite responsible for the drug’s therapeutic effects as an ACE inhibitor. The parent drug, benazepril, itself is inactive until this metabolic activation takes place.

Excretion

Benazepril and its active metabolite, benazeprilat, are primarily excreted by the kidneys. About 95% of benazeprilat is eliminated in the urine, while a smaller portion is excreted via the feces. The drug has a half-life of approximately 10-11 hours, allowing for once-daily dosing in most cases.

PHARMACODYNAMICS

Benazepril’s pharmacodynamics are centered on its active metabolite, benazeprilat, which functions as an angiotensin-converting enzyme (ACE) inhibitor. By blocking ACE, benazeprilat prevents the conversion of angiotensin I to angiotensin II, a potent vasoconstrictor. This leads to vasodilation, reduced blood pressure, decreased aldosterone secretion, and lowered sodium and water retention. These effects make benazepril effective in managing hypertension and heart failure by reducing vascular resistance and decreasing the workload on the heart.

ADMINISTRATION

Benazepril is administered orally, usually in tablet form. It is typically taken once daily, with or without food, as food does not significantly affect its absorption. The dosage may be adjusted based on the patient’s response and medical condition. It’s important to follow the prescribing healthcare provider’s instructions and maintain consistent dosing times for optimal effectiveness.

DOSAGE AND STRENGTH

Benazepril is commonly available in tablet strengths of 5 mg, 10 mg, 20 mg, and 40 mg. For adults with hypertension, the usual starting dose is 10 mg once daily. Depending on the patient’s response, the dose can be adjusted, typically ranging from 20 mg to 40 mg once daily. Lower starting doses may be recommended for individuals with kidney impairment or those already taking diuretics. It is important to follow the healthcare provider’s instructions for dosing to ensure safe and effective treatment.

FOOD INTERACTIONS

Benazepril has minimal food interactions. It can be taken with or without food, as food does not significantly affect its absorption or effectiveness. However, patients should avoid excessive intake of potassium-rich foods or potassium supplements while taking benazepril, since the drug can increase potassium levels in the blood and raise the risk of hyperkalemia. As always, it’s best to follow your healthcare provider’s advice regarding diet and medication.

DRUG INTERACTIONS

Benazepril, an ACE inhibitor, can interact with various medications such as other antihypertensives, potassium supplements, NSAIDs, lithium, and antidiabetic drugs. These interactions may cause dangerously low blood pressure, elevated potassium levels, or kidney damage. It’s important to consult your doctor or pharmacist about all medications, supplements, or herbal products you are taking before beginning benazepril.

CONTRAINDICATIONS

Benazepril is contraindicated in people allergic to it or other ACE inhibitors, those with a history of angioedema from ACE inhibitors, pregnant women, and patients with severe kidney problems or bilateral renal artery stenosis. It should not be used with aliskiren in diabetic or kidney-impaired patients.

SIDE EFFECTS

Common side effects:

• Cough.

• Dizziness and lightheadedness.

• Headache.

• Fatigue and drowsiness.

• Nausea.

Serious side effects:

• Angioedema.

• Kidney problems.

• High potassium levels (hyperkalemia).

• Liver damage.

• Severe low blood pressure (hypotension).

OVERDOSE

The primary and most common sign of a benazepril overdose is severe low blood pressure, which can cause: 

• Dizziness.

• Fainting.

• Weakness.

• Blurred vision.

• Lethargy.

• Rapid or irregular heartbeat (in some cases). 

• Acute kidney failure.

• Electrolyte imbalances.

TOXICITY

Benazepril toxicity primarily occurs with overdose, leading to an exaggeration of its therapeutic effects, mainly severe low blood pressure (hypotension). Other toxic effects can arise from drug interactions, pre-existing health conditions, or severe adverse reactions such as angioedema.