Generic name: Verapamil hydrochloride.

Other brand names: Calan SR, Isoptin, Isoptin SR, Verelan.

Calan is a calcium channel blocker. It increases the amount of oxygen that reaches the heart muscle. 

Quick Facts About Calan


Used to treat various types of chest pain (angina). Also used to treat irregular heartbeat and high blood pressure. Sustained release formula (SR.) used for high blood pressure only. Has been prescribed to treat manic depression and panic attacks.

Calan Dosage

May be taken with or without food. Sustained release formulas should be taken with food, and must be swallowed whole. Take exactly as prescribed, even if you are feeling well. Take regularly; otherwise, condition may worsen.

  • Usual adult dose: Calan and Isoptin: in general, no more than 480 milligrams per day is ever prescribed. For chest pain — 80 to 120 milligrams 3 times per day. For chest pain in seniors or those with decreased liver function — 40 milligrams 3 times per day. For irregular heartbeat — people on Digitalis — 240 to 320 milligrams per day, divided into 3 or 4 doses; people not on Digitalis — 240 to 480 milligrams per day, divided into 3 or 4 doses. For high blood pressure only — 80 milligrams 3 times per day, ranging from 360 to 480 milligrams total per day. For high blood pressure only in seniors and smaller individuals — 40 milligrams 3 times per day. Sustained Release and Verelan: for sustained release — 180 milligrams taken in the morning; smaller person may require 120 milligrams. For seniors — 120 milligrams taken in the morning.
  • Usual child dose: not generally prescribed for children.
  • Missed dose: take as soon as possible, unless almost time for next dose. In that case, do not take missed dose, go back to regular schedule. Do not double doses.

Calan Side Effects

Overdose symptoms:

no specific information available; however, if overdose is suspected, should be under observation for 48 hours. If you suspect an overdose, immediately seek medical attention.

More common side effects: congestive heart failure, constipation, dizziness, fatigue, fluid retention, headache, low blood pressure, nausea, rash, shortness of breath, slow heartbeat.

Less common Calan side effects: angina, blurred vision, breast development in males, bruising, chest pain, confusion, diarrhea, difficulty sleeping, drowsiness, dry mouth, excessive milk secretion, fainting, fever and rash, flushing, hair loss, heart attack, hives, impotence, increased urination, joint pain, limping, loss of balance, muscle cramps, pounding heartbeat, rash, shakiness, skin peeling, sleepiness, spotty menstruation, sweating, tingling or pins and needles, upset stomach.


Inform your doctor before combining Calan with:

Amiodarone (Cordarone); ace inhibitor-type blood pressure medications such as Capoten and Vasotec; beta-blocker-type blood pressure medications such as Inderal, Lopressor, and Tenormin; Carbamazepine (Tegretol); Chloroquine (Aralen); Cimetidine (Tagamet); Cydosporine (Sandimmune); Dantrolene (Dantrium); Digitalis (Lanoxin); Disopyramide (Norpace); diuretics such as Lasix and HydroDIURIL; Flecainide (Tambocor); Glipizide (Glucotrol); Imipramine (Tofranil); inhalation anesthetics; Lithium (Lithonate); nitrates such as Transderm Nitro and Isordil; Phenobarbital; Phenytoin (Dilantin); Quinidine (Quinidex); Rifampin (Rifadin); Theophylline (Theo-Dur); vasodilator-type blood pressure medications such as Loniten or other high blood pressure medications such as Minipress.

No known food/other substance interactions. 

Special Cautions

If pregnant or planning to become pregnant, inform ? your doctor immediately. Appears in breast milk; could affect a nursing baby.

Lower dose is generally prescribed for seniors.

Not generally prescribed for children.

  • Do not take if sensitive to or had an allergic reaction to this or other brands, or other calcium channel blockers. Should not take if you have: low blood pressure, certain types of heart disease, Duchenne’s dystrophy, heartbeat irregularities, kidney disease, or liver disease.
  • Check with your doctor before major exertion or exercise.
  • Inform your doctor if you experience light-headed-ness.

Note: provides accurate and independent information prescription pills, over-the-counter medicines and natural products. This material is provided for educational purposes only and is not intended for medical advice, diagnosis or treatment. If you have questions about  dosage, or Calan side effects, please contact your healthcare provider.