DIHYDROPYRIDINE 5%W/W PREMIX (Each kg contains: Dihydropyridine 500mg)

Indications

• Hypertension
• Angina pectoris
• Vasospastic angina
• Chronic stable angina

Dosage

Children: Refer to the BNF for Children for paediatric dosing information.

Adults: Refer to the BNF for specific adult dosing information based on the particular dihydropyridine agent being used.

Mechanism of action

Dihydropyridines selectively inhibit L-type calcium channels, reducing intracellular calcium levels in vascular smooth muscle cells. This results in smooth muscle relaxation, vasodilation, and ultimately lowers systemic vascular resistance and blood pressure. They do not significantly affect cardiac contractility or conduction due to their preferential action on vascular tissues.

Pharmacodynamics

Dihydropyridines exhibit dose-dependent vasodilatory effects. By reducing peripheral vascular resistance, they decrease the workload on the heart. Their pharmacodynamic profile includes a rapid onset of action with a prolonged duration of effect, making them suitable for once-daily dosing. They are generally well tolerated but can cause peripheral edema and reflex tachycardia as side effects.

Pharmacokinetics

Dihydropyridines are well absorbed from the gastrointestinal tract, with a variable first-pass metabolism affecting their bioavailability. Peak plasma concentrations are typically reached within 1 to 3 hours post-administration. They are extensively metabolized in the liver through cytochrome P450 enzymes, primarily CYP3A4. The elimination half-life varies among different dihydropyridines, influencing dosing frequency. Excretion occurs mainly via urine, with a small percentage excreted unchanged.

Contra-indications

• Hypersensitivity to dihydropyridine or any excipients
• Severe hypotension
• Cardiogenic shock
• Aortic stenosis

Adverse effects

• Headache
• Dizziness
• Flushing
• Peripheral edema
• Palpitations
• Gingival hyperplasia

Interactions

• CYP3A4 inhibitors and inducers may alter the metabolism of dihydropyridine
• Concomitant use with other antihypertensives may lead to additive hypotensive effects

Precautions

• Use with caution in patients with heart failure
• Monitor blood pressure regularly during treatment
• Caution in elderly patients due to potential for increased sensitivity

Pregnancy

Use during pregnancy only if clearly needed and the benefits outweigh the risks, as there are limited studies on safety.

Breast-feeding

Use with caution, as it is not known whether dihydropyridine is excreted in human milk.

Storage

Store in a cool, dry place, away from direct sunlight and out of reach of children.

Formulations

• Tablets
• Extended-release formulations