Calan SR (Verapamil)
Medication information written by Dr. Larisa Roybal, PharmD
Updated - January 25, 2021
Calan SR (verapamil) Medication Information
Uses
Calan SR is a calcium ion influx inhibitor (slow-channel blocker or calcium ion antagonist) that exerts its pharmacologic effects by modulating the influx of ionic calcium across the cell membrane of the arterial smooth muscle as well as in conductive and contractile myocardial cells.
Calan SR is indicated for the treatment of hypertension, to lower blood pressure. Lowering blood pressure reduces the risk of fatal and nonfatal cardiovascular events, primarily strokes and myocardial infarctions.
Dosage
There are oral capsules available in several different strengths:
- 120 mg
- 180 mg
- 240 mg
Side Effects
The most common side effects of Calan SR include:
- Constipation
- Dizziness
- Nausea
- Hypotension
- Headache
- Edema
- CHF
- Pulmonary edema
- Fatigue
- Elevated liver enzymes
Speak with your doctor or pharmacist for a full list of side effects that applies to you.
Precautions
Since verapamil is highly metabolized by the liver, it should be administered cautiously to patients with impaired hepatic function. Severe liver dysfunction prolongs the elimination half-life of verapamil to about 14 to 16 hours.
It has been reported that verapamil decreases neuromuscular transmission in patients with Duchenne's muscular dystrophy, and that verapamil prolongs recovery from the neuromuscular blocking agent vecuronium. It may be necessary to decrease the dosage of verapamil when it is administered to patients with attenuated neuromuscular transmission.
About 70% of an administered dose of verapamil is excreted as metabolites in the urine. Verapamil is not removed by hemodialysis. Until further data are available, verapamil should be administered cautiously to patients with impaired renal function.
Interactions
Some of the common drug interactions with Calan SR:
- Alcohol
- Beta-blocker
- Digoxin
- Disopyramide
- Flecainide
- Quinidine
- Lithium
- Rifampin
- Phenobarbital
Speak with your doctor or pharmacist for more information.
Storage
Store at controlled room temperature (59-77ºF). Protect from light and moisture.
Pharmacist Tips
- Since the half-life of verapamil increases during chronic dosing, maximum response may be delayed.
- Upward titration should be based on therapeutic efficacy and safety evaluated approximately eight hours after dosing.
- Safety and effectiveness in pediatric patients have not been established.
Calan SR FAQs
Can I take this with food?
Calan SR should be taken with food.
Can I take this if I am pregnant?
There are no adequate and well-controlled studies in pregnant women. Because animal reproduction studies are not always predictive of human response, this drug should be used during pregnancy only if clearly needed. Verapamil crosses the placental barrier and can be detected in umbilical vein blood at delivery.
Can I take this while breastfeeding?
Verapamil is excreted in human milk. Because of the potential for adverse reactions in nursing infants from verapamil, nursing should be discontinued while verapamil is administered.
Can this medication be titrated?
Upward titration should be based on therapeutic efficacy and safety evaluated weekly and approximately 24 hours after the previous dose.
Related Drugs
Reference:
Calan SR {package insert}. New York, NY: Pfizer; 2017.
https://www.accessdata.fda.gov/drugsatfda_docs/label/2017/019152s041lbl.pdf
Author: Dr. Larisa Roybal, PharmD
Dr. Roybal is a board-certified pharmacotherapy specialist who has practiced in both ambulatory and acute care settings. Her pharmacy interests include oncology and general inpatient pharmacy.
The above information is an educational aid only. It is not intended as medical advice for individual conditions or treatments. Talk to your doctor, nurse or pharmacist before following any medical regimen to see if it is safe and effective for you.
