Diltiazem

Calcium channel blocker (non-dihydropyridine), Antianginal, Antiarrhythmic (class IV), Antihypertensive

Diltiazem

Cardizem, Tiazac, Cartia XT, Dilacor XR, Taztia XT, Matzim LA

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Titration strategies

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Effects

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Pharmacy

Starting dose

ER 180-240 mg PO once daily; IR 30 mg PO QID; IV 0.25 mg/kg over 2 min for acute rate control, then 5-15 mg/h infusion

Preparations

IR 30, 60, 90, 120 mg tablets; multiple ER capsules and tablets 60-420 mg; IV 5 mg/mL

US FDA Max

~480 mg/d (oral); IV per protocol

Common uses

Classification(s)

Classes

Calcium channel blocker (non-dihydropyridine), Antianginal, Antiarrhythmic (class IV), Antihypertensive

Pharmacology

Routes

Oral (IR, multiple ER formulations), IV

Onset

IV: 3-7 minutes (rate control); PO IR: 30-60 minutes; ER: hours

Duration

IR: 4-8 hours; ER: 24 hours

Half-life

3-4.5 hours (IR); 5-7 hours (ER; effective duration 24 hours via formulation)

Bioavailability

~40% (oral; extensive first-pass via CYP3A4)

Pregnancy

Limited data; labetalol/nifedipine generally preferred. Crosses placenta.^{[citation needed]}

Legal status

Rx-only in US

Purported mechanism

Diltiazem is a benzothiazepine non-dihydropyridine calcium channel blocker; unlike amlodipine and nifedipine, it has substantial AV nodal and cardiac myocyte L-type channel blockade in addition to vascular smooth muscle effects, producing rate control plus modest vasodilation.▲0▼ Avoid in HFrEF (negative inotropy). CYP3A4 substrate AND moderate inhibitor — interacts substantially with statins (especially simvastatin), tacrolimus, cyclosporine, and many other CYP3A4 substrates.