Comprehensive medication guide to Diltiazem XR including estimated pricing, availability information, side effects, and how to find it in stock at your local pharmacy.
Estimated Insurance Pricing
$0-$15 copay for generic at Tier 1-2 on most commercial plans and Medicare Part D; prior authorization is rarely required for generic diltiazem ER.
Estimated Cash Pricing
$10-$60 retail for generic 30-day supply; as low as $5.91-$13 with GoodRx or SingleCare coupons. Brand-name Cardizem CD/LA runs $80-$350+ per month without insurance.
Medfinder Findability Score
60/100
Summarize with AI
On this page
Diltiazem XR is an extended-release formulation of diltiazem hydrochloride, a non-dihydropyridine calcium channel blocker in the benzothiazepine chemical class. First approved by the FDA in 1982, it is one of the most widely prescribed cardiovascular medications in the world. The "XR" designation indicates extended-release technology that allows once-daily dosing.
Brand names include Cardizem CD, Cardizem LA, Cartia XT, Dilacor XR, Dilt-XR, Tiazac, Taztia XT, and Matzim LA. Generic versions are widely available and significantly more affordable. These formulations are NOT interchangeable — each uses a different drug delivery mechanism and requires a separate prescription if switching.
Diltiazem XR is FDA-approved for hypertension (high blood pressure) and chronic stable angina (chest pain). It is also used off-label for rate control in atrial fibrillation, migraine prophylaxis, and selected cases of pulmonary hypertension.
We have a 99% success rate finding medications, even during nationwide shortages.
Need this medication?
Diltiazem XR works by selectively blocking L-type voltage-gated calcium channels in the walls of blood vessels and in cardiac muscle cells. Calcium is required for muscle cell contraction — by blocking its entry, diltiazem prevents the contraction of vascular smooth muscle and reduces the force and rate of cardiac contractions.
This produces three key cardiovascular effects: vasodilation (relaxation and widening of blood vessels, lowering blood pressure), negative chronotropy (slowing of heart rate via SA node suppression), and negative dromotropy (slowing of AV node conduction, useful for rate control in arrhythmias). The combined effect reduces cardiac oxygen demand — the mechanism behind its efficacy in angina.
Unlike dihydropyridine calcium channel blockers (amlodipine, nifedipine), which primarily affect blood vessel walls, diltiazem is a non-dihydropyridine that acts on both vascular smooth muscle AND cardiac muscle. This makes it uniquely suited for conditions requiring both blood pressure control and heart rate management.
120 mg — extended-release capsule
Starting dose option; used for hypertension and angina
180 mg — extended-release capsule
Common starting dose for hypertension
240 mg — extended-release capsule
Common maintenance dose for hypertension and angina
300 mg — extended-release capsule
Higher dose maintenance for hypertension
360 mg — extended-release capsule
High-dose option; also available as extended-release tablet
120 mg — extended-release tablet
Cardizem LA-type; starting dose for hypertension
180 mg — extended-release tablet
Cardizem LA-type; common starting dose
240 mg — extended-release tablet
Cardizem LA-type; common maintenance dose
300 mg — extended-release tablet
Cardizem LA-type; higher maintenance dose
360 mg — extended-release tablet
Cardizem LA-type; high-dose maintenance
420 mg — extended-release tablet
Cardizem LA-type; highest available tablet dose; 540mg/day max total
Diltiazem XR presents a unique findability challenge: there is no official FDA-declared shortage of oral extended-release forms as of 2026, yet many patients experience real difficulties filling their prescription at their local pharmacy. The core problem is formulation non-interchangeability.
The FDA has not granted AB-ratings across the different Diltiazem ER formulation types (Cardizem CD, Cardizem LA, Tiazac, Cartia XT, Dilacor XR, Matzim LA). Each uses a different drug delivery mechanism and different pharmacokinetics. Pharmacists cannot substitute one for another without a new prescription. This means a shortage of one formulation type cannot be offset by stock of another — creating what effectively are localized shortages even when the drug is nationally available.
Higher strengths (300 mg, 360 mg, 420 mg) are particularly prone to localized stock-outs at community pharmacies. If you're having trouble finding your specific formulation, medfinder can contact pharmacies near you to find which ones have your exact prescription in stock — saving hours of calls and avoiding unnecessary trips.
Diltiazem XR is not a DEA-scheduled controlled substance, so there are no special prescribing restrictions. Any licensed healthcare provider with prescription authority in your state can prescribe it. Common prescribers include:
Primary care physicians (PCPs) — most common prescribers for hypertension and angina
Cardiologists — for complex cardiac conditions including arrhythmias and refractory angina
Internal medicine physicians — frequently manage hypertension and cardiovascular comorbidities
Nurse practitioners (NPs) — can prescribe in all 50 states with varying supervision requirements
Physician assistants (PAs) — can prescribe in all 50 states
Geriatricians — frequently prescribe for older adults managing multiple cardiovascular conditions
Nephrologists — prescribe for hypertension management in chronic kidney disease
Telehealth prescribing is available for Diltiazem XR with no additional federal restrictions. Platforms such as Teladoc, MDLive, and Amazon Clinic can evaluate and prescribe for hypertension management in most states. Same-day appointments are commonly available.
No. Diltiazem XR is not a DEA-scheduled controlled substance. It is classified as a standard prescription medication with no special federal prescribing restrictions related to scheduling. Any licensed prescriber with prescription authority — including primary care physicians, cardiologists, internists, nurse practitioners, and physician assistants — can prescribe it.
Because it is not a controlled substance, Diltiazem XR prescriptions can be refilled without special procedures, can be called in or sent electronically by any prescriber, and can be transferred between pharmacies with standard transfer protocols. Prescriptions can also be issued via telehealth visits without the additional restrictions that apply to controlled substances.
The following side effects occur in more than 2% of patients and are generally manageable:
Lower limb edema (ankle and leg swelling)
Headache
Dizziness
Fatigue
Bradycardia (slow heart rate)
Sinus congestion
First-degree AV block (visible on ECG, usually not clinically significant)
Rash
Second- or third-degree AV block (severe bradycardia, fainting, heart block)
Worsening heart failure (sudden shortness of breath, rapid weight gain)
Acute hepatic injury (jaundice, dark urine, upper right abdominal pain)
Stevens-Johnson Syndrome / toxic epidermal necrolysis (blistering or peeling skin)
Severe hypotension (sudden weakness, dizziness, fainting)
Know what you need? Skip the search.
Verapamil ER
Most pharmacologically similar — also a non-dihydropyridine CCB that lowers blood pressure AND slows heart rate. Higher constipation risk. Generic available for $4-$20/month.
Amlodipine
Dihydropyridine CCB — excellent for pure hypertension but does NOT slow heart rate. Widely available at virtually every pharmacy. Generic as low as $4/month.
Metoprolol Succinate ER
Beta-blocker — alternative for rate control plus blood pressure. Avoid in asthma/COPD. Very affordable generic ($4-$15/month).
Lisinopril
ACE inhibitor — excellent for hypertension, especially in patients with diabetes or CKD. No heart rate effect. Very inexpensive ($4-$10/month generic).
Prefer Diltiazem XR? We can find it.
Dantrolene
majorContraindicated. Combination can cause cardiovascular collapse and fatal hyperkalemia.
Ivabradine (Corlanor)
majorContraindicated. Diltiazem inhibits ivabradine metabolism, causing severe bradycardia.
Flibanserin (Addyi)
majorContraindicated. Diltiazem inhibits CYP3A4 metabolism of flibanserin, causing severe hypotension and syncope.
Beta-blockers (metoprolol, atenolol, carvedilol)
majorAdditive AV nodal depression; risk of severe bradycardia, heart block, or heart failure. Requires close monitoring.
Digoxin
majorDiltiazem increases digoxin levels 20-30% via P-glycoprotein inhibition. Risk of digoxin toxicity. Monitor digoxin levels and reduce dose if needed.
Amiodarone
majorAdditive AV conduction slowing. Risk of sinus arrest and severe bradycardia. Use with caution.
Cyclosporine / Tacrolimus
moderateDiltiazem inhibits CYP3A4 metabolism of these immunosuppressants, significantly raising their levels and nephrotoxicity risk.
Simvastatin / Lovastatin
moderateDiltiazem inhibits CYP3A4; simvastatin must be limited to 10 mg/day. Risk of myopathy and rhabdomyolysis. Prefer pravastatin or rosuvastatin.
Ranolazine (Ranexa)
moderateDiltiazem inhibits CYP3A4 metabolism of ranolazine. Limit ranolazine to 500 mg twice daily when used with diltiazem.
Grapefruit / Grapefruit Juice
moderateInhibits CYP3A4 in gut wall and liver, increasing diltiazem blood levels. Avoid grapefruit and Seville oranges while taking diltiazem XR.
St. John's Wort
moderateStrong CYP3A4 inducer that significantly reduces diltiazem blood levels, potentially making it less effective. Avoid concurrent use.
CYP3A4 inhibitors (azole antifungals, clarithromycin, erythromycin)
moderateCan increase diltiazem exposure, potentially causing excessive blood pressure lowering or bradycardia.
Diltiazem XR is a proven, effective, and affordable medication for managing hypertension and chronic stable angina. With generic versions widely available for as little as $6-$13/month with a discount card, cost is rarely the main barrier. The bigger challenge in 2026 is navigating the formulation fragmentation that causes localized pharmacy stock-outs even when the drug is nationally available.
Understanding that different Diltiazem XR formulations are not interchangeable — and working proactively with your prescriber and pharmacist to manage supply — is the key to uninterrupted therapy. Setting up 90-day mail-order fills, refilling early, and having a plan for temporary formulation switches can prevent the dangerous gaps in blood pressure control that result from running out.
If you're having trouble locating your Diltiazem XR prescription, medfinder can contact pharmacies near you to find which ones have your specific formulation and strength in stock — saving you hours of phone calls and frustration.
Medfinder Editorial Standards
Our medication guides are researched and written to help patients make informed decisions. All content is reviewed for accuracy and updated regularly. Learn more about our standards
ChatGPT
Claude
Perplexity
Grok
Gemini