Calcium channel blockers are antianginal and antihypertensive. They inhibit the move ment of calcium ions across the membranes of cardiac and arterial muscle cells. This in hibition of transmembrane calcium flow re sults in the depression of impulse formation in specialized cardiac pacemaker cells, slow ing of the velocity of conduction of the car diac impulse, depression of myocardial con tractility, and dilation of coronary arteries and arterioles and peripheral arterioles. These effects lead to decreased cardiac work, de creased cardiac energy consumption, and increased delivery of oxygen to myocardial cells.

Indications

Treatment of angina pectoris caused by coro nary artery spasm (Prinzmetal’s variant angina), chronic stable angina (effort associated angina), hypertension, arrhyth mias (supraventricular, those related to digoxin [verapamil]), subarachnoid hem orrhage (nimodipine)

Orphan drug use in the treatment of inter stitial cystitis, hypertensive emergencies, mi graines, Raynaud’s syndrome

Unlabeled uses: Treatment of preterm labor, Raynaud’s phenomenon, acute ischemic stroke, vascular headaches, hypertensive emergencies

Contraindications and cautions

Contraindicated with heart block, allergy to calcium channel blockers, sick sinus syndrome, ventricular dysfunction, preg nancy.

Use cautiously during lactation.

Adverse effects

CNS: Dizziness, lightheadedness, head ache, asthenia,fatigue, nervousness,sleep disturbances, blurred vision

CV: Peripheral edema, angina,hypoten sion, arrhythmias, bradycardia, AV block, asystole

Dermatologic: Flushing, rash,dermati tis, pruritus, urticaria

GI: Nausea, diarrhea, constipation,flatu lence, cramps, hepatic injury

Other: Nasal congestion, cough, fever, chills, shortness of breath, muscle cramps, joint stiffness, sexual difficulties

Interactions

Drugdrug

Increased effects with cimet idine, ranitidine

Increased toxicity of cyclo sporine Drugfood

Increased serum levels when combined with grapefruit juice

Nursing considerations

Assessment

History: Allergy to calcium channel block ers, sick sinus syndrome, heart block, ven tricular dysfunction; pregnancy; lactation

Physical: Skin lesions, color, edema; ori entation, reflexes; P, BP, baseline ECG, peripheral perfusion, auscultation; R, Calcium Channel Blockers 38 ? Calcium Channel Blockers

Adverse effects

in italics are most common; those in bold are lifethreatening. U Do not crush. adventitious sounds; liver evaluation, nor mal GI output; LFTs

Interventions

Monitor patient carefully (BP, cardiac rhythm, and output) while drug is being titrated to therapeutic dose; the dosage may be increased more rapidly in hospitalized patients under close supervision.

Ensure that patients do not chew or divide sustainedrelease tablets.

Taper dosage of betaadrenergic blockers be fore beginning calcium channel blocker therapy.

Protect drug from light and moisture.

Ensure ready access to bathroom.

Provide comfort measures for skin rash, headache, nervousness.

Establish safety precautions if CNS changes occur.

Position patient to alleviate peripheral edema.

Provide frequent small meals if GI upset oc curs.

Teaching points

Do not chew or divide sustainedrelease tablets. Swallow whole.

Avoid grapefruit juice while taking this drug.

You may experience these side effects: Nau sea, vomiting (frequent small meals may help); dizziness, lightheadedness, vertigo (avoid driving, operating hazardous ma chinery; avoid falling); muscle cramps, joint stiffness, sweating, sexual difficulties (should stop when the drug therapy is stopped; dis cuss with your health care provider if these become too uncomfortable).

Report irregular heartbeat, shortness of breath, swelling of the hands or feet, pro nounced dizziness, constipation.

Representative drugs

amlodipine clevidipine diltiazem felodipine isradipine nicardipine nifedipine nimodipine nisoldipine verapamil