(3) Cautions and warnings. Metaraminol may induce arrhythmias in large
doses. Furthermore, the drug should be used with caution with patients who have heart
disease, thyroid disease, hypertension, or diabetes.
(1) Pharmacological effects. Phenylephrine is a powerful alpha stimulator
with little or no effect on beta-receptors.
Indications. Phenylephrine has a variety of uses. These include:
(b) Vasopressor. The drug is used as a vasopressor for hypotension
associated with spinal anesthesia and neurogenic shock.
Mydriatic. The drug is used to produce mydriasis (dilatation of the
(3) Cautions and warnings. The drug is contraindicated in hypertension and
existing ventricular tachycardia. Phenylephrine can induce cardiac irregularities.
Indications. This drug is used as a nasal decongestant.
(2) Caution and warning. Prolonged use of this agent as a nasal
decongestant may produce chemical rhinitis.
(3) Side effects. Tetrahydrozoline may cause sneezing, stinging or burning
of the mucous membranes, insomnia, or tachycardia.
Agents listed in m and n, below, are referred to as incomplete
sympathomimetics. They produce topical vasoconstriction of the nasal
mucosa or conjunctiva. They have no direct effect on the myocardium or
on the smooth muscle of the bronchioles. However, they do relax the
intestine. Remember, although both the intestine and the bronchi are
smooth muscles, they are affected by different receptors. Intestinal relaxation
is moderated by alpha2 receptors and bronchi relaxation by beta2 receptors.
m. Xylometazoline (Otrivin).
Indications. Xylometazoline is used as a nasal decongestant.
(2) Caution and warning. No significant caution and warning is associated
with the drug.