Pseudoephedrine / terfenadine Side Effects
Applies to pseudoephedrine/terfenadine: oral tablet extended release
Terfenadine use has been shown to cause prolongation of the QT interval. Most cardiovascular events related to terfenadine occur in patients taking higher than the recommended dose of 60 mg twice daily, those with higher than normal terfenadine serum concentrations, or in patients at risk for cardiac events. Patients with liver disease are at risk due to accumulation of the drug. Other predisposing factors for cardiovascular toxicity include congenital forms of QT interval prolongation, coronary artery disease, and electrolyte disorders including hypokalemia and hypomagnesemia. Although rare, arrhythmias have been reported in patients receiving recommended doses without apparent risk factors.
Pseudoephedrine causes vasoconstriction which generally does not produce hypertension, but may be problematic for patients with preexisting hypertension. Arrhythmias may be produced in predisposed patients. Rarely, pseudoephedrine has been reported to cause coronary artery spasm and chest pain.[Ref]
Cardiovascular system adverse effects have been associated with the use of terfenadine. Reported effects include dizziness, syncopal episodes, palpitations, ventricular arrhythmias, including torsades de pointes, cardiac arrest, and cardiac death. Pseudoephedrine generally causes a significant rise in heart rate. Hypertension and arrhythmias due to pseudoephedrine may be problematic in susceptible patients.[Ref]
The nervous system is rarely affected by terfenadine, however headaches are reported in approximately 6% of treated patients. Terfenadine has not been shown to cause significant drowsiness, sedation, or impair psychomotor skills.
Pseudoephedrine produces nervous system stimulation, resulting in tremor, anxiety, and nervousness. Insomnia is reported in up to 30% of pseudoephedrine-treated patients. Headache may also occur in patients receiving pseudoephedrine.[Ref]
Gastrointestinal effects of terfenadine are rare and include nausea and dry mouth. Pseudoephedrine may cause anorexia and gastric irritation in approximately 5% of patients. Dry mouth, nose, or throat may also be caused by pseudoephedrine.[Ref]
A study of the effects of terfenadine on the urination of 8 healthy male volunteers and 11 males with benign prostatic hypertrophy was not able to confirm a consistent effect on voiding characteristics.[Ref]
Hypersensitivity reactions to pseudoephedrine may occur. Fixed drug eruptions secondary to pseudoephedrine have been reported.[Ref]
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Some side effects may not be reported. You may report them to the FDA.