SIDE EFFECTS
Possible adverse reactions include nervousness, insomnia, restlessness, headache, nausea, or gastric irritation. These reactions seldom, if ever, require discontinuation of therapy. Urinary retention may occur in patients with prostatic hypertrophy.
Side effects may include:
Anxiety, convulsions, depression, difficulty breathing, difficulty urinating (in men with an enlarged prostate), hallucinations, headache, inability to sleep or difficulty sleeping, increased heart beat, irritability, irritated stomach, nausea, nervousness, paleness, palpitations, restlessness, tremor, weakness, vomiting
DRUG INTERACTIONS
Phenyephrine HCl w/guaifenesin long acting tablets should not be used in patients taking monoamine oxidase inhibitors or other sympathomimetics.
Do not take Entex LA (guaifenesin and phenylephrine) if you are taking a medication classified as an MAO inhibitor, including the antidepressants Nardil and Parnate. Avoid other stimulating drugs such as Proventil, Ventolin, and many decongestants. Interactions can also occur with the following:
Bromocriptine (Parlodel)
Mecamylamine (Inversine)
Methyldopa (Aldomet)
Reserpine (Diupres, Hydropres)