Atropine (C17H23NO3 = 287.04) is an alkaloid derived from the leaves and root of Atropa Belladonna, the Deadly Nightshade.

Pharmacodynamics.

Central Nervous System. - Atropine primarily stimulates the motor divisions of the brain, thence the medulla and cord; this is followed by marked depression tending towards paralysis.

Unstriped muscle is made less responsive, probably because of a paralysis at the myoneural junction.

Respiration. - Centric stimulation quickens and deepens respiration; secondary depression produces slow, shallow breathing.

Heart. - Atropine paralyzes the inhibitory terminations of the vagus in the heart, thereby quickening heart action, and making it less efficient.

Blood-pressure usually rises owing to stimulation of splanchnic constrictors. Large doses may lower B. P. through heart action.

Eye. - Pupil is dilated through paralysis of myoneurals of circularis muscle; muscle of accommodation also paralyzed.

Alimentary Tract. - Secretions lessened, and activity diminished, because of depression of terminal filaments of vagus.

Secretory Glands. - Depressed through paralysis of terminations of secretory fibers.

Metabolism markedly increased (Edsall).

Temperature is often elevated; means unknown; possibly centric.

Absorption is rapid from mucosa and subcutaneous tissues.

Excretion. - Atropine is largely oxidized in the tissues. Small amounts may escape in the urine.

Local Action. - Atropine depresses the sensory endings in the skin.

Tolerance. - Rapidly acquired by rabbits; very little by man.

Symptoms.

Therapeutic Doses. Oral and faucial dryness. Dilatation of pupil. Increased pulse. Quickened respiration. Flushing of face and neck. Restlessness. Garrulity. Depression. Lassitude.

Toxic Doses. Symptoms of small doses plus thirst and dysphagia; nausea, headache and vertigo; widely dilated pupil, hoarseness and dysphonia; weak, rapid, thready pulse; exaggerated movements, hysteria and delirium, tremors (convulsions), depression, stupor, coma; death from asphyxia.

Therapeutics.

Atropine may be used to lessen secretions; to relax spasm of the involuntary muscles, especially of the intestines; to counteract depressions of the brain and medulla; and as a diagnostic aid to ophthalmologists. Dosage.

Extractum Belladonnae Foliorum, 0.005 to 0.03 Gm. Tinctura Belladonnae Foliorum, 0.3 to 1 mil. Atropina, 0.0003 to 0.0008 Gm. Atropinae Sulphas, same dose as for Atropina. Scopolamine, or Hyoscine, resembles closely the action of Atropine, except that it depresses the central nervous system from the start. Hence, it is used in some cases as a hypnotic.

Dosage: Scopolamine Hydrobromide, 0.0003 to 0.0008 Gm.

Atropine 67

Crimson = stimulation. Violet = depression.