ATC Group: S01F Mydriatics and cycloplegics

Atropine is an antimuscarinic agent which competitively antagonises acetylcholine at postganglionic nerve endings, thus affecting receptors if the exocrine glands, smooth muscle, cardiac muscle and the central nervous system.

Cyclopentolate is an antimuscarinic agent used topically in the eye as a mydriatic and cycloplegic. The effects are similar to those of atropine, but with a more rapid onset and a shorter duration of action.

Ephedrine is a sympathomimetic amine acting directly on the alpha and beta receptors and indirectly by increasing the release of noradrenaline by the sympathetic nerve endings. As with any sympathomimetic agent, ephedrine stimulates the central nervous system, the cardiovascular system, the respiratory system, and the sphincters of the digestive and urinary systems.

Methscopolamine is an anticholinergic. The mechanism of action of methscopolamine is as a cholinergic antagonist.

Phenylephrine is a sympathomimetic agent with mainly direct effects on adrenergic receptors. It has predominantly alpha adrenergic activity and is without stimulating effects on the central nervous system. The sympathomimetic effect of phenylephrine produces vasoconstriction which in turn relieves nasal congestion.

Scopolamine is a naturally occurring belladonna alkaloid and has anticholinergic properties. It acts as a competitive antagonist to acetylchloline and other parasympathomimetic agents. Its mechanism of action in the central nervous system in preventing motion sickness has yet to be elucidated. Scopolamine produces classical symptoms of parasympathetic blockade.

Tropicamide is an anticholinergic which blocks the responses of the sphincter muscle of the iris and the ciliary muscle to cholinergic stimulation thus dilating the pupil (mydriasis).