Rinfocan- Prescription Drug Information for Canadians
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BRAND NAMES
Adalat, 10 mg
Adalat 5 mg
Adalat PA 10 mg
Adalat PA 20 mg
Adalat XL 30 mg
Adalat XL 60 mg
(Also available in generic form)
TYPE OF DRUG
Calcium channel blocker.
PRESCRIBED FOR
Angina pectoris; Prinzmetal's angina; high blood pressure.
Nifedipine has also been prescribed to prevent migraine headaches and to treat
asthma, heart failure, Raynaud's disease, disorders of the esophagus, gall bladder and
kidney stone attacks, and severe high blood pressure associated with pregnancy
(preterm labor).
GENERAL INFORMATION
Nifedipine is one of a growing number of calcium channel blockers to be marketed in
the United States. Calcium channel blockers work by blocking the passage of calcium
into heart and smooth muscle. Since calcium is an essential factor in muscle
contraction, any drug that affects calcium in this way will interfere with the contraction
of these muscles. When this happens the amount of oxygen used by the muscles is
also reduced. Therefore, Nifedipine is used in the treatment of angina, a type of heart
pain related to poor oxygen supply to the heart muscles. Also, Nifedipine dilates
(opens) the vessels that supply blood to the heart muscles and prevents spasm of these
arteries. Nifedipine affects the movement of calcium only into muscle cells; it does not
have any affect on calcium in the blood.
Nifedipine capsules contain liquid medicine. In cases where the drug is needed in the
blood as rapidly as possible, the capsules may be punctured and their contents
squeezed under the tongue; medicine is rapidly absorbed into the blood in this manner.
Thus, Nifedipine capsules are useful in situations where extremely high blood
pressure must be rapidly lowered. Some researchers feel that biting the capsule in
your mouth and swallowing the contents gets the medicine into your blood even faster
than keeping it under the tongue.
CAUTIONS AND WARNINGS
Nifedipine may cause unwanted low blood pressure in some people taking it for
reasons other than hypertension.
Patients taking a beta-blocking drug who begin taking Nifedipine may develop heart
failure or increased angina pain. Angina pain may also increase when your Nifedipine
dosage is increased.
Do not take this drug if you have had an allergic reaction to it in the past.
Nifedipine may interfere with one of the mechanisms by which blood clots form,
especially if you are also taking Aspirin. Call your doctor if you develop unusual
bruises, bleeding, or black-and-blue marks.
People with severe liver disease break down Nifedipine much more slowly than
people with less severe disease or normal livers. Your doctor should take this into
account when determining your Nifedipine dosage.
PREGNANCY/BREAST-FEEDING
Nifedipine crosses into the blood circulation of a developing baby. It has been used to
treat severe high blood pressure associated with pregnancy and not caused any
unusual effect on the baby. Nevertheless, pregnant women, or those who might
become pregnant while taking this drug, should not take it without their doctors'
approval. When the drug is considered essential by your doctor, the potential risk of
taking the medicine must be carefully weighed against the benefit it might produce.
Small amounts of Nifedipine may pass into breast milk, but the drug has caused no
problems among breast-fed infants. You must consider the potential effect on the
nursing infant if breast-feeding while taking this medicine.
SENIORS
Older adults are more sensitive to the effects of this drug because it takes longer to
pass out of their bodies. Follow your doctor's directions and report any side effects at
once.
POSSIBLE SIDE EFFECTS
Common side effects are dizziness; light-headedness; flushing; a feeling of warmth;
headache; weakness; nausea; muscle cramps, inflammation, and pains; swelling of the
arms or legs; nervousness; mood changes; heart palpitations; heart failure; heart attack;
difficulty breathing; coughs; fluid in the lungs; wheezing; stuffy nose; and sore throat.
Less common side effects include low blood pressure, unusual heart rhythms, angina
pains, fainting, shortness of breath, diarrhea, cramps, constipation, stomach gas, dry
mouth, taste changes, frequent urination (especially at night), stiffness and
inflammation of the joints, arthritis, shakiness, jitteriness, psychotic reaction, anxiety,
memory loss, paranoia, hallucinations, tingling in the hands or feet, tiredness, muscle
weakness, liver inflammation, blurred vision, ringing or buzzing in the ears, difficulty
sleeping, unusual dreams, respiratory infections, anemia, bleeding, bruising,
nosebleeds, swollen gums, weight gain, reduced white-blood-cell counts, difficulty
maintaining balance, itching, rash, hair loss, painful breast inflammation, unusual
sensitivity to the sun, severe skin reactions, fever, sweating, chills, and sexual
difficulties. Nifedipine can cause increases in certain blood-sugar and some enzyme
tests.
DRUG INTERACTIONS
Nifedipine may interact with beta-blocking drugs to cause heart failure, very low blood
pressure, or an increased incidence of angina pain. However, in many cases these
drugs have been taken together with no problem.
Nifedipine may cause unexpected blood pressure reduction in patients already taking
medicine to control their high blood pressure through interaction with other
antihypertensive drugs.
Cimetidine and Ranitidine increase the amount of Nifedipine in the blood and may
account for a slight increase in Nifedipine's effect.
The combination of Quinidine (for abnormal heart rhythm) and Nifedipine must be
used with caution because it can produce low blood pressure, very slow heart rate,
abnormal heart rhythms, and swelling in the arms or legs.
Nifedipine can, rarely, increase the effects of oral anticoagulant (blood-thinning) drugs.
Nifedipine can increase the effects of Theophylline products (for asthma and other
respiratory problems).
FOOD INTERACTIONS
Nifedipine can be taken without regard to food or meals.
USUAL DOSE
30 to 120 milligrams per day of regular Nifedipine. No patient should take more than
180 milligrams per day.
The usual dose for the sustained-release version of Nifedipine (Adalat XL) is 30 to
60 milligrams taken once a day.
Do not stop taking Nifedipine abruptly. The dosage should be gradually reduced over
a period of time.
OVERDOSAGE
Overdose of Nifedipine can cause low blood pressure. If you think you have taken an
overdose of Nifedipine, call your doctor or go to a hospital emergency room.
ALWAYS bring the medicine bottle.
SPECIAL INFORMATION
Call your doctor if you develop constipation, nausea, very low blood pressure,
swelling in the hands or feet, difficulty breathing, increased heart pains, or dizziness or
light-headedness or if other side effects are particulary bothersome or persistent.
If you are taking Nifedipine for high blood pressure, be sure to continue taking your
medicine and follow any instructions for diet restriction or other treatments. High blood
pressure is a condition with few recognizable symptoms; it may seem to you that you
are taking medicine for no good reason. Call your doctor or pharmacist if you have any
questions.
If you take Adalat XL be sure not to break or crush the tablets. You may notice an
empty tablet in your stool. This is not cause for alarm, because the medicine is
normally released from the sustained-release tablet without actually destroying it.
It is important to maintain good dental hygiene while taking Nifedipine and to use
extra care when using your toothbrush or dental floss because of the chance that the
drug will make you more susceptible to some infections.
If you forget a dose of Nifedipine, take it as soon as you remember. If it is almost time
for your next regularly scheduled dose, skip the forgotten dose and continue with your
regular schedule. Do not take a double dose.
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