Isradipine (tradenames DynaCirc, Prescal) is a calcium channel blocker of the dihydropyridine class. It is usually prescribed for the treatment of high blood pressure in order to reduce the risk of stroke and heart attack. It was patented in 1978 and approved for medical use in 1989.

Medical uses

Isradipine is given as either a 2.5 mg or 5 mg capsule.

Side effects

Common side effects include: Serious side effects include:

Drug interactions

It is advised that those using isradipine not take dolasetron (Anzemet), as both agents can cause a dose-dependent PR interval and QRS complex prolongation. Itraconazole (Onmel/Sporanox) exhibits a negative inotropic effect on the heart and thus could spur an additive effect when used concomitantly with isradipine. Itraconazole also inhibits an important cytochrome liver enzyme (CYP 450 3A4) which is needed to metabolize isradipine and other calcium channel blockers. This will increase plasma levels of isradipine and could cause an unintentional overdose of the medication. Caution is advised when administering both agents together. Tizanidine demonstrates anti-hypertensive effects and should be avoided in patients taking isradipine due to the possibility of synergism between both medications. The antibiotic rifampin lowered plasma concentrations of isradipine to below detectable limits. Cimetidine increased isradipine mean peak plasma levels. A downward dose adjustment may be necessary with this particular instance of polypharmacy. Severe hypotension was reported with fentanyl anesthesia when it was combined with other calcium channel blockers. Even though isradipine, another calcium channel blocker, has not been used in conjunction with fentanyl anesthesia in any studies, caution is advised.

Overdose

Symptoms of an isradipine overdose include:

Stereochemistry

Isradipine contains a stereocenter and consists of two enantiomers, more precisely atropisomers. This is a racemate, i.e. a 1: 1 mixture of (R)- and the (S)-forms: