Hyper-reactive individuals may display ephedrine-like reactions such as tachycardia, palpitations, headache, dizziness, or nausea. Sympathomimetics have been associated with certain untoward reactions including fear, anxiety, nervousness, restlessness, tremor, weakness, pallor, respiratory difficulty, dysuria, insomnia, hallucinations, convulsions, CNS depression, arrhythmias, and cardiovascular collapse with hypotension. No serious side effects have been reported with the use of guaifenesin.

Read the Guaifenex PSE 60 (guaifenesin pseudoephedrine extended-release tablets) Side Effects Center for a complete guide to possible side effects »

Do not prescribe this product for use in patients that are now taking a prescription MAOI (certain drugs for depression, psychiatric or emotional conditions, or Parkinson's disease), or for 14 days after stopping the MAOI drug therapy. Beta-adrenergic blockers and MAOI inhibitors may potentiate the pressor effect of pseudoephedrine. Concurrent use of digitalis glycosides may increase the possibility of cardiac arrhythmias. Sympathomimetics may reduce the hypotensive effects of guanethidine, mecamylamine, methyldopa, reserpine and veratrum alkaloids. Concurrent use of tricyclic antidepressants may antagonize the effects of pseudoephedrine.

Drug/Laboratory Test Interactions: Guaifenesin may increase renal clearance for urate and thereby lower serum uric acid levels. Guaifenesin may produce an increase in urinary 5-hydroxy-indoleacetic acid and may therefore interfere with the interpretation of this test for the diagnosis of carcinoid syndrome. It may also falsely elevate the VMA test for catechols. Administration of this drug should be discontinued 48 hours prior to the collection of urine specimens for such tests.

Last reviewed on RxList: 8/5/2008
This monograph has been modified to include the generic and brand name in many instances.