Drugs Group 1

Calcium channel blocker

Diltiazem interferes with the entry influx of calcium intocardiac and vascular smooth muscle. In addition it slowsthe rate of the SA node and conduction velocity throughthe AV node. Diltiazem’s ability to relax coronaryarteries, as well as its negative inotropic and negativechronotropic qualities makes it a useful antianginal. It isalso used as an antihypertensive. However in theprehospital setting, we use it primarily as anantidysrhythmic so its ability to slow the conductionthrough the AV node is most pertinent.

To control rapid ventricular rates associated with atrial fibrillationand atrial flutter, and SVT refractory to adenosine

Should not be administered to any patient with severehypotension or cardiogenic shock, ventricular tachycardia(wide-complex tachycardia), atrial flutter or atrial fibrillation inpatients with WPW (may precipitate ventricular fibrillation)

Should not be administered to patients receiving intravenous β-blockers because of an increased risk of CHF, bradycardia, andasystole

0.25 mg/kg over 2 minRepeat 0.35 mg/kg if no response in 15 minMaximum single dose: 20-25 mg.Maintenance infusion of 5–15 mg/hr

Electrolyte, Antidysrhythmic

Increases the magnesium levels, correcting for possiblehypomagnesemia, which is associated with cardiacdysrhythmias. Magnesium interferes with neuromusculartransmission, reducing muscle contractions in seizuresand bronchoconstriction

Torsades de Pointes, v-fib / v-tach in patients felt to behypomagnesemic, refractory v-fib, preeclampsia and eclampsia,refractory bronchoconstriction, TCA OD (if QRS is wide)

Shock, heart block

Calcium chloride is antidote if respiratory depression ensues,caution in renal failure patients

May block effect of digitalis

1-2 g IV push

1-2 g IV, over 5-60 min

2-4 g IV, over 5-60 min

2 g IV, over 5-60 min

Beta-blocker (β1 predominance)

Selectively antagonizes beta-1 adrenergic receptors,causing a reduction in heart rate, systolic bloodpressure, and cardiac output. It is thought to beprotective of the heart and is used to reduce potentialcomplications in selected patients who have suffered anAMI. Metoprolol has proved effective in reducing theincidence of ventricular fibrillation and chest pain inthese patients, thus reducing overall patient mortality inthe post-MI period

Suspected or definite hemodynamically stable AMI

Heart rate less than 45 bpm, systolic BP less than 100,moderate to severe CHF, first-degree heart block with a PRinterval greater than 0.24 sec, second-degree heart block(Type I or II), third-degree heart block, any patient with earlyor late signs of shock

Bradycardia, hypotension, dyspnea, and wheezing

5 mg slow IV, q 5 min x 3 total doses if vitals remain stable