BRAND NAME: NORVASC
AVAILABLE IN
2.5 mg. 5 mg and
10 mg TABLETS
BACKGROUND:
Muscle is ultimately composed of protein filaments. These filaments
are arranged in parallel in an overlapping fashion. When muscles
contract, the fibers are able to slide across one another shortening
the over all length to up to one third of the original length.
Muscle contraction is made possible by the release of calcium from
storage within the muscle cell (in a structure called the “sarcoplasmic
reticulum.”) Nerve stimulation causes the release of calcium which
allows muscle contraction to happen. No calcium, no muscle contraction.
There are three types of muscle within the body: skeletal muscle
(the muscles under voluntary control which we use to move), smooth
muscle (the involuntary muscle which provides muscle tone in our
intestines, blood vessels, and other structures we do not consciously
control), and heart muscle (which has some characteristics of both
the other two types). In the control of hypertension, the goal is
the reduction of blood pressure. We would like to relax the muscle
tone in the arteries that carry blood to our tissues. The heart must
pump against the muscle tone of the arteries and must work harder
if there is high pressure in the arteries.
Amlodipine besylate is what is called a “calcium channel blocker.”
These drugs work by blocking the calcium needed for muscle contraction
in either primarily heart muscle or primarily arterial muscle. Amlodipine
besylate is one of the calcium channel blockers that works primarily
on arterial muscle. Its overall effect is to relax the arterial muscles
so that they dilate and the blood pressure within them drops.
Hypertension is an important problem in both people and pets. Amlodipine
besylate has become the most popular blood pressure medication for
hypertensive cats. It has not worked well in dogs.
HOW THIS MEDICATION IS USED:
Amlodipine besylate is used to treat high blood pressure in the
cat. High blood pressure is a common consequence of numerous conditions
including kidney failure, hyperthyroidism, hypertrophic cardiomyopathy,
and more. For more information on hypertension in pets click here.
Treatment for hypertension should be considered when a cat’s systolic
blood pressure exceeds 160 mmHg.
Amlodipine besylate may be given with or without food. Its peak
activity occurs approximately 6-9 hours after oral administration
in humans (feline data not available). Amlodipine besylate is generally
given once a day in the cat. Expect your veterinarian to recommend
periodic rechecks to measure blood pressure and evaluate the retinas
of signs of bleeding.
SIDE EFFECTS:
In humans, 7.3% of people taking this drug report headache which
makes headache the most common side effect of amlodipine besylate.
Of course, we do not have a good way of detecting headache in our
pets.
Infrequent side effects reported in cats include elevations in renal
blood parameters, drop in blood potassium levels, lethargy, increase
in heart rate, and weight loss.
INTERACTIONS WITH OTHER DRUGS:
Hypotension (blood pressure dropping too low) generally does not
occur with amlodipine besylate unless it is combined with another
drug that drops blood pressure. Other drugs of this type might include:
fentanyl, diuretics such as furosemide, ACE inhibitors such as enalapril,
or beta-blockers such as propranolol.
CONCERNS AND CAUTIONS:
Missing even one dose can lead to a significant rise in blood pressure
and a return of clinical symptoms of high blood pressure.
Patients with liver disease remove this drug from their systems
very slowly thus necessitating modification of the dosing regimen.
Amlodipine besylate should not be used in pregnancy.
Amlodipine besylate has some (usually insignificant) effects on
the heart. It will slightly reduce the strength of contraction. This
could be significant in patients with a history of heart failure
and the drug should be used with caution in this situation.
Amlodipine Besylate Medical Center Amlodipine Besylate
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