BRAND NAME: CARDIZEM
Muscle contraction is governed by the flow of calcium through what are called "voltage-gated calcium channels." When these channels are blocked by drugs, less calcium can flow through the channels. This results in a weaker muscle contraction. Blood calcium levels are not altered by this blockade.
The voltage-gated calcium channels that one might wish to block are located in heart muscle and in blood vessels. The use of calcium channel blockers would lead to a more relaxed and therefore dilated blood vessel which, in turn, translates to lower blood pressure. The heart ends up with less resistance to pump against, meaning that the heart does not have to work as hard. In situations where the heart muscle might be overworked, this might lead to a more efficient and healthier heart.
Diltiazem also affects the electrical conduction of the heart such that electrical conduction is slowed. This means that the heart rate also slows, allowing for a longer filling time for the heart between pumps.
HOW THIS MEDICATION IS USED:
Diltiazem is most commonly used in the treatment of hypertrophic cardiomyopathy in the cat. In this condition, the heart muscle becomes stiff and inflexible plus the filling chambers of the heart become smaller. The muscle-bound heart cannot fill normally for these reasons and since it cannot fill normally, it sends forth less blood with each pump. To meet the oxygen demands of the body, the heart pumps faster since it is pumping out less blood per pump.
By using a calcium channel blocker such as diltiazem, the heart may fill more efficiently.
Diltiazem might also be used in the treatment of hypertension.
The most commonly reported side effect in the cat is vomiting. Other side effects include: low blood pressure and consequent listlessness, slow heart rate, heart arrythmias, weight loss and reduced appetite
INTERACTIONS WITH OTHER DRUGS:
Diltiazem should not be used with beta-blockers (heart medications which might compound the low blood pressure side effect) such as atenolol or propranolol. Even beta-blocker eyedrops as might be used in glaucoma treatment could create adverse blood pressure reactions.
Cimetidine (an antacid) may increase the blood levels of diltiazem (making the effects of diltiazem stronger). Ranitidine, another antacid, also has this effect but not as strongly.
Medications that are stronger when used with diltiazem include: benzodiazepine tranquilizers (such as diazepam and alprazolam) and cyclosporine (an immunomodulator used to treat immune-mediated disease as well as allergy)
Medications that are weaker when used with diltiazem include: buspirone (an anti-anxiety medication).
Concurrent use of diltiazem with cisapride (a bowel motility modifier most commonly used for the treatment of obstipation/severe constipation) could lead to cardiac arrhythmia (disturbances in the electrical conduction of the heart).
CONCERNS AND CAUTIONS:
Page posted: 12/22/10