The active principle of belladonna, the juice of the deadly nightshade plant. It acts by antagonising the action of the PARASYMPATHETIC NERVOUS SYSTEM, temporarily impairing vision by paralysing ACCOMMODATION and inhibiting the action of some of the nerves in the AUTONOMIC NERVOUS SYSTEM. The drug relaxes smooth muscle. It has an effect on the activity of almost all the exocrine glands of the body, including the SWEAT GLANDS of the skin and the SALIVARY GLANDS in the mouth. Atropine relieves spasm by paralysing nerves in the muscle of the intestine, bile ducts, bladder, stomach, etc. It has the power, in moderate doses, of markedly increasing the rate of the heartbeat, though by very large doses the heart, along with all other muscles, is paralysed and stopped.
Atropine drops are used to dilate the pupil for more thorough examination of the interior of the eye, or to draw the iris away from wounds and ulcers on the centre of the eye. They also soothe the pain caused by light falling on an inflamed eye, and are further used to paralyse the ciliary muscle and so prevent accommodative changes in the eye while the eye is being examined with the OPHTHALMOSCOPE. Given by injection, atropine is used before general ANAESTHESIA to reduce secretions in the bronchial tree. The drug can also be used to accelerate the heart rate in BRADYCARDIA resulting from coronary thrombosis.