-Inhibition of L-type calcium channels leads to decreases myometrial SM → decreased SM contraction

available in sustained and immediate release oral formulations, 10-60mg

Selectively dilates arterial resistance vessels. The ↓in arterial BP elicits sympathetic reflexes, with resulting tachycardia and positive inotropy.

Thus, arteriolar resistance and blood pressure are lowered, contractility and segmental ventricular function are improved, and heart rate and cardiac output are modestly increased.

lipid solubility moderately low, minimal BBB

~90%

0.62-1.12 L/kg

Hepatic via CYP3A4 to inactive metabolites

Urine (60% to 80% as inactive metabolites); faeces

2-5 hours (↑ in liver failure)

PO 10-20mg BD.

(CCB) Ca channel blocker – Class II

Level 3

prototypical dihydropyridine calcium channel blocker

primarily arterial vasodilatory e¬ffects with little effect on electrical conduction in the heart. Used primarily for HTN, angina and in preterm labour

should not be used for acute blood pressure reduction in hypertensive emergencies. Peripheral oedema is a common side e¬ffect, 2-3 weeks post initiation of therapy.
Other side e¬ffects are related to its vasodilating properties: flushing, vertigo, headaches, hypotension and parathesias. Risk of coronary vasospasm with acute withdrawal.

PO.
BA 60% Well absorbed moderate first pass metabolism
on/dur ~20 minutes / not stated

TOCOLYTIC

Level 3 for Tocolysis

Level 3 for anti-hypertensive (see in relevant table)

dihydropyridine derivative

Suppression of threatened or established preterm labour before 34 weeks gestation where not contraindicated.

(Angina, HTN, PIH, Raynaud’s, Coronary spasm during angio)

Inhibition of hypoxic pulmonary vasoconstriction, Impaired platlet aggregation, Headache,
flushing and dizziness, Peripheral oedema

PO
Loading – 20mg, further 2 doses 30minly if contractions persist
Maintenance 20-40mg QID for up to 48hrs

Should not be used together with Salbutamol