Catecholamine-depleting drugs, eg, reserpine, may have an additive effect when given with beta blocking agents. Patients treated concurrently with Esmolol HCl and a catecholamine depletor should therefore be closely observed for evidence of hypotension or marked bradycardia, which may result in vertigo, syncope, or postural hypotension.
A study of interaction between Esmolol HCl and warfarin does not alter warfarin plasma levels. Esmolol HCl concentrations were equivocally higher when given with warfarin but this is not likely to be clinically important.
When digoxin and Esmolol HCl were concomitantly administered intravenously to normal volunteers, there was a 10-20% increase in digoxin blood levels at some time points. Digoxin did not affect Esmolol HCl pharmacokinetics. When intravenous morphine and Esmolol HCl were concomitantly administered in normal subjects, no effect on morphine blood levels was seen, but Esmolol HCl steady-state blood levels were increased by 46% in the presence of morphine. No other pharmacokinetic parameters were changed.
The effect of Esmolol HCl on the duration of succinylcholine-induced neuromuscular blockade was studied in patients undergoing surgery. The onset of neuromuscular blockade by succinylcholine was unaffected by Esmolol HCl, but the duration of neuromuscular blockade was prolonged form 5 minutes to 8 minutes.
Although the interactions observed in these studies do not appear to be of major clinical importance, Esmolol HCl should be titrated with caution in patients being treated concurrently with digoxin, morphine, succinylcholine or warfarin.
While taking beta-blockers, patients with a history of severe anaphylactic reaction to a variety of allergens may be more reactive to repeated challenge, either accidental, diagnostic, or therapeutic. Such patients may be unresponsive to the usual doses of epinephrine used to treat allergic reaction.
Caution should be exercised when considering the use of Esmolol HCl and verapamil in patients with depressed myocardial function. Fatal cardiac arrests have occurred in patients receiving both drugs. Additionally, Esmolol HCl should not be used to control supraventricular tachycardia in the presence of agents which are vasoconstrictive and inotropic such as dopamine, epinephrine and norepinephrine because of the danger of blocking cardiac contractility when systemic vascular resistance is high.