BENZOTHIAZEPINE: DILTIAZEM
GENERAL DESCRIPTION
Diltiazem is less potent calcium channel blockers than verapamil and dihydrpyridines. It belongs to the benzothiazepine group of calcium channel blockers. Diltiazem is extensively used as antianginal and antiarrhythmic drug. To control tachycardia, diltiazem is also given after antithyroid therapy in such patient where beta blockers are contraindicated.
GENERIC NAME: Diltiazem
BRAND NAME Cartia, Dilacor, Tiazac, Cardizem
MECHANISM OF ACTION
Cardiovascular response of diltiazem is shown in following steps
Firstly, diltiazem decrease myocardial contractile force which reduces myocardial oxygen requirements. Secondly, diltiazem 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 markedly effected by diltiazem thus decreases atrioventricular nodal conduction and is effective medicine in supraventricular tachycardia and also decreasing ventricular responses in atrial fibrillation or flutter.
Cardiovascular effects of Diltiazem
- Vasodilation: Moderate
- Suppression of cardiac contractility: Low
- Suppression of automaticity (SA node): High
- Suppression of conduction (AV node): High
PHARMACOKINETICS
Diltiazem is taken orally and have 40-65% bioavailability. It can also be given as intravenous route. The plasma half-life of diltiazem is 3-4 hours. Diltiazem is metabolized by a CYP3A4 enzyme or cytochrome P450 system.
INDICATIONS
- Decrease coronary vascular resistance
- Supraventricular tachyarrhythmia
- Decrease coronary vascular resistance
- Dysrhythmia
- Variant Angina
- Exertional Angina
- Unstable angina
- Myocardial Infarction
- Hypertension
- Raynaud’s phenomenon
CONTRAINDICATIONS
- Ventricular dysfunction
- SA and AV nodal conduction disturbance
- Systolic blood pressure below 90 mmHg
- Hypersensitivity
- Hepatic cirrhosis (can use with dose adjustment)
- Second or third degree heart block
- Bradycardia
SIDE EFFECTS & ADVERSE EFFECTS
- Ankle swelling (oedema)
- Dizziness
- Flushing
- Urinary retention (less)
- Headache
- Dizziness
- Nausea
- Vomiting
DRUG INTERACTION
- Grape fruit juice may increase the bioavailability of diltiazem.
- Diltiazem can cause digoxin toxicity when given concurrently.
- When use with Quinidine, diltiazem can cause hypotension.
- The concurrent use of aprepitant and diltiazem increases the plasma level of both drugs.
- NSAIDs may reduce the hypotensive effects of diltiazem. NSAIDs may cause internal bleeding and bruises when used with diltiazem.
- Drugs containing azole can increase the serum level of diltiazem, which further increase adverse effect of oedema in patients
- Chlorpromazine and other phenothiazine can cause severe hypotension when used with diltiazem.
- Dantrolene may cause acute hyperkalemia and cardiovascular collapse when given with diltiazem.
- Combination of diuretics and diltiazem case 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.