DiltiazemDiltiazem Hydrochloride

About Diltiazem

Diltiazem slows calcium entry into heart and blood vessel muscle, widening arteries and slowing conduction through the heart. Cardizem tablets are labeled for chronic stable angina and angina from coronary artery spasm, starting at 30 mg four times a day, before meals and at bedtime, and usually reaching 180 to 360 mg a day. Cardizem CD and its generics, including Cartia XT, are labeled for high blood pressure, chronic stable angina and angina from spasm; for blood pressure they start at 180 to 240 mg once a day, usually 240 to 360 mg, and for angina at 120 or 180 mg. Tiazac, Dilt-XR, Cardizem LA and their generics are labeled for high blood pressure and chronic stable angina. The injection, given into a vein with ECG monitoring, temporarily controls a fast heart rate in atrial fibrillation or flutter and converts PSVT to a normal rhythm; no oral form is labeled for atrial fibrillation.

There is no boxed warning. It must not be taken with sick sinus syndrome or second- or third-degree heart block unless a working ventricular pacemaker is in place, with systolic blood pressure under 90, after a heart attack with lung congestion on X-ray, or with an allergy to it. It can slow the heart too much or block conduction, especially with beta blockers or digoxin, worsen heart failure in people with a weak heart, lower blood pressure, and rarely injure the liver, usually within one to eight weeks of starting; a skin reaction that persists means stopping it. Swelling of the lower legs is among the most common side effects, with headache, dizziness, tiredness, a slow pulse and rash also reported.

The FDA rates generics of Cardizem CD as AB3 and generics of Tiazac as AB4; Dilt-XR is rated AB2; and Cardizem LA has AB-rated generics. The Tiazac label allows the capsule to be opened and sprinkled on a spoonful of applesauce that is not hot, swallowed at once without chewing; Dilt-XR is swallowed whole on an empty stomach in the morning; and the Cardizem CD label says to avoid alcohol, which sped the drug’s release in laboratory tests. The Cardizem CD interaction section, updated in April 2025, now also calls diltiazem a substrate and inhibitor of P-glycoprotein, a drug transporter. Animal studies showed harm to the fetus, and diltiazem passes into breast milk, so the labels call for choosing between breastfeeding and the medicine.

Taking Diltiazem

How to take it

Immediate-release tablets three or four times a day; extended-release forms once a day at about the same time, swallowed whole and not chewed or crushed unless your product’s label allows opening the capsule. Do not stop it without talking to the prescriber.

If you miss a dose

Take it as soon as you remember, unless it is almost time for the next dose; then skip the missed dose and carry on as usual. Do not take a double dose.

Storage

At room temperature, away from excess heat and humidity, in a tightly closed container out of reach of children.

Interactions to know about

Simvastatin is limited to 10 mg and diltiazem to 240 mg a day when taken together; lovastatin levels also rise, so a statin not cleared by CYP3A4 is preferred when possible. It raises midazolam, triazolam, buspirone, carbamazepine, cyclosporine, quinidine and digoxin levels; beta blockers, digoxin and clonidine add to slowing of the heart; ivabradine is avoided; rifampin and other CYP3A4 inducers are avoided when possible; and cimetidine raises its levels.

This summarizes the official prescribing information. Your prescriber’s and pharmacist’s instructions, and the leaflet that comes with your medicine, take priority.

Why the cash price for Diltiazem differs from pharmacy to pharmacy

Generic immediate-release tablets have several makers and Cardizem CD-type capsules many, and both cost pharmacies little, so a quote is mostly the dispensing fee and markup, which differ between pharmacies. Tiazac-type capsules, Dilt-XR and the extended-release tablets have fewer makers.

Because the families are not rated equivalent to one another, a prescription can be filled only with the named product or a generic in its family. A prescription that names a brand and blocks substitution is priced as a brand.

Ways to pay less for Diltiazem without insurance

• Check which product your prescription names, ask for a generic rated equivalent to it, and make sure the prescription does not block substitution.
• Ask whether your diltiazem is on the pharmacy’s flat-price generic list, and compare more than one pharmacy.
• If your product has few generic makers, ask the prescriber whether a Cardizem CD-type capsule would suit you.
• Once your dose is stable, ask for a ninety-day supply.
• Upload the prescription to Script Unlock so licensed pharmacies can quote their cash price. You pay the pharmacy directly.

Questions to ask your pharmacist about Diltiazem

1. 1.Is my generic rated equivalent to the product on my prescription?
2. 2.Do I need to change my simvastatin, lovastatin or other medicines while I take it?
3. 3.Which pulse, dizziness or swelling symptoms mean I should call?
4. 4.Can I open my capsule, or must I swallow it whole?

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