Drug Interactions between pseudoephedrine / terfenadine and sevoflurane

Before receiving anesthesia with sevoflurane, let your doctor know if you are currently using terfenadine. Combining these medications can increase the risk of an irregular heart rhythm that may be serious and potentially life-threatening, although it is a rare side effect. You may be more susceptible if you have a heart condition called congenital long QT syndrome, other cardiac diseases, conduction abnormalities, or electrolyte disturbances (for example, magnesium or potassium loss due to severe or prolonged diarrhea or vomiting). Talk to your doctor if you have any questions or concerns. Your doctor may already be aware of the risks, but has determined that this is the best course of treatment for you and has taken appropriate precautions and is monitoring you closely for any potential complications. You should also be closely monitored by the surgical staff while you are under anesthesia. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

Consumer information for this interaction is not currently available.

GENERALLY AVOID: The administration of volatile general anesthetics during therapy with indirect-acting sympathomimetics (e.g. methylphenidate, ephedrine) or their derivatives may increase the risk of hypertension and/or cardiac arrhythmias. The proposed mechanism is anesthetic-induced myocardial sensitization to the stimulation caused by sympathomimetics.

MANAGEMENT: Until more information is available, caution is advisable if volatile general anesthetics are administered concomitantly with indirect-acting sympathomimetics or any of their derivatives. If the combination is required, dosage adjustments are recommended, and the patient's hemodynamic status should be closely monitored. When surgery is planned, it is recommended that indirect-acting sympathomimetics or their derivatives be discontinued prior to the day of surgery. Prescribing information for individual products should be consulted.