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Generic Name: Verapamil (slow release)
Brand Name(s):
Information updated: April 1, 2000
Overview
Calan belongs to a class of medicines called calcium channel blockers.
Because of their safety and effectiveness, these drugs have helped
revolutionize the treatment of high blood pressure.
Other uses of
calcium channel blockers include treatment of irregular heart rhythms and
angina.
There is even some preliminary research that suggests some of
these compounds may be able to prevent migraine headaches, ease nighttime leg
cramps, asthma and Raynaud's disease, and perhaps reduce atherosclerosis.
Despite these future possibilities, Calan SR has been approved only for
the treatment of hypertension.
Side Effects and Interactions
One of the most common side effects of Calan is
constipation. Although bothersome, this can often be controlled with fluid and
fiber or a bulk-forming laxative such as psyllium.
Another reaction to
be alert for is low blood pressure, which may show up as lightheadedness and
dizziness.
Although uncommon, other adverse reactions include headache,
fluid retention leading to swelling of arm and legs, nausea, tiredness, rash and
slowed heart rate. Report any symptoms or suspected side effects to your
physician promptly.
Calan can interact with a number of other drugs,
including several that are used to treat high blood pressure or heart
conditions, the asthma medicine theophylline, the anticonvulsant Tegretol, the
transplant medication Sandimmune and the anti-tuberculosis agent rifampin.
The popular antidepressant Prozac may increase the likelihood of side
effects from Calan.
Over-the-counter calcium supplements can reduce the
effectiveness of Calan. Check with your doctor and pharmacist to make sure Calan
is safe in combination with any other drugs you take.
Special Precautions
Although Calan may be prescribed for a variety of cardiac indications, there are some serious heart conditions that may be worsened by this drug.
Your doctor should be fully informed about any heart problem, kidney disease, liver disease, low blood pressure and muscular dystrophy.
Careful monitoring is called for in any of these cases due to an increased risk of toxicity.
In addition, older people may be more sensitive to the blood-pressure-lowering effects of Calan SR.
Taking the Medicine
The manufacturer recommends that this sustained-release formulation should be taken with food,
preferably in the morning with breakfast.
If a second dose is needed it should be swallowed
approximately 12 hours later.
Do not stop taking Calan SR suddenly, as this could lead to
complications.
Your doctor will tell you how to taper off gradually if you no longer need this medication.
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Joe Graedon is a pharmacologist. Teresa Graedon holds a doctorate in medical anthropology and is a nutrition expert. Their syndicated radio show can be heard on public radio.
© 2000