Dihyropyridine: Amlodipine
GENERAL DESCRIPTION
Amlodipine is a good choice of drug for elderly patients. Amlodipine has no effects on heart rate like other calcium channel blockers. Amlodipine is more potent than verapamil and diltiazem.
GENERIC NAME: Amlodipine
BRAND NAME: Norvasc, Acord, Amlibon
MECHANISM OF ACTION
Amlodipine produce both peripheral arterial vasodilation and coronary dilation. Cardiovascular response of amlodipine is shown in following steps
Firstly, Amlodipine decrease myocardial contractile force which reduces myocardial oxygen requirements. Secondly, amlodipine inhibits calcium influx into arterial smooth muscles resulted in decreased arteriolar tone and systemic vascular resistance. This process decreased the arterial and intraventricular pressure. As a result of all these steps, left ventricular wall stress decline and which reduces myocardial oxygen requirements. SA nodes and AV nodes, which are mainly composed of calcium channels are less marked by amlodipine. Therefore it is not effected medicine in arrhythmias or atrial fibrillation.
Cardiovascular effects of Amlodipine
- Vasodilation: High
- Suppression of cardiac contractility: Low
- Suppression of automaticity (SA node): Low
- Suppression of conduction (AV node): No
PHARMACOKINETICS
Amlodipine is taken once daily. Amlodipine has a slow absorption and a prolonged effect. Oral bioavailability is 65-90%. Plasma half-life is 35-50 hours which is longer hence there is less chance of tachycardia than other calcium channel blockers. Amlodipine is metabolized by CYP3A4 enzyme or cytochrome P450 system.
INDICATIONS
- Hypertension
- Decrease coronary vascular resistance
- Dysrhythmia
- Variant Angina
- Exertional Angina
- Unstable angina
- SR preparation for hypertension
- Myocardial Infarction
- Heart Failure
CONTRAINDICATIONS
- Hypersensitivity
- Hepatic cirrhosis (can use with dose adjustment)
- Second or third degree heart block
- Bradycardia
- Ventricular dysfunction
- SA and AV nodal conduction disturbance
- Systolic blood pressure below 90 mmHg
SIDE EFFECTS & ADVERSE EFFECTS
- Ankle swelling
- Dizziness
- Flushing
- Urinary retention (less)
- Headache
- Dizziness
- Nausea
- Vomiting
DRUG INTERACTION
- Grape fruit juice may increase the bioavailability of amlodipine.
- Amlodipine can cause digoxin toxicity when given concurrently.
- When use with Quinidine, amlodipine can cause hypotension.
- The concurrent use of aprepitant and diltiazem increases the plasma level of both drugs.
- NSAIDs may reduce the hypotensive effects of amlodipine. NSAIDs may cause internal bleeding and bruises when used with amlodipine.
- Drugs containing azole can increase the serum level of amlodipine, which further increase adverse effect of oedema in patients
- Chlorpromazine and other phenothiazine can cause severe hypotension when used with amlodipine.
- Combination of diuretics and amlodipine can increase antihypertensive effects.
NURSING INTERVENTION
- Inquire complete health history of patient.
- Monitor blood pressure and pulse before and during therapy
- Check fluid intake and output.
- Check peripheral oedema, rashes and other s/s related to the medicine
- Monitor BUN, serum potassium, creatinine, AST, ALT, serum bilirubin level
PATIENT EDUCATION
- Counsel the right time and dosage of medicine.
- Instruct patient how to count pulse and if pulse is less than 55 inform health practitioner.
- Avoid the use of alcohol while taking medicine.
- Don’t adjust the missed dose.
- Avoid OTC and NSAIDs concurrently with medicine.
- Consult doctor prior to the use of herbal or other multivitamins supplements
- Instruct patient to take caution while changing the posture.
- Counsel patient with the possible side effects of the medicine and inform if feel any.