Other systemic blood vessels will also be constricted which causes side effects. Oral decongestant products are safe to use in recommended doses in healthy individuals but may have adverse effects in persons with heart disease, hypertension, diabetes, hyperthyroidism, urinary retention or an enlarged prostate. They are contraindicated in persons receiving or having received MAO inhibitors in the past 2 weeks. The therapeutic effectiveness of phenylephrine as a nasal decongestant has been questioned, especially at the usual oral dose.
Tricyclic antidepressants have an additive sympathomimetic effect with phenylephrine.
The elderly are more likely to have adverse reactions to sympathomimetics. Overdose may cause hallucinations, convulsions, CNS depression and death. There is an abuse potential with pseudoephedrine using high doses for a stimulant effect. Patients with open angle glaucoma may have a slight increase in introcular pressure. Short term or occasional use is not contraindicated in patients with well-controlled open angle glaucoma.