Large Doses.—Arrest digestion, cause nausea and vomiting, greatly increase perspiration, prevents the conductivity of nerves, depresses the heart and circulation, impairing oxidation and lowering temperature; it contracts the pupil by stimulating the motor nerve of the eye (in horses it dilates the pupil) and causes intense puritis (itching), especially of the nose, often retention of the urine and soon profound sleep; in some cases coma or delirium, leaving as after-effects nausea, depression, constipation, vertigo, anorexia, nasal puritis and fetid pathological secretions.
Morphine and codeine compared with the action of opium. Morphine is more anodyne and hypnotic; it causes more intense puritis (itching) is less stimulant, less convulsant, less constipating and diaphoretic.
Codeine is a motor paralyzant; it exalts the spinal cord more than morphine and affects the cerebrum less, producing muscular tremors in excess of sedation; it reduces the urinary sugar in diabetes and has a selective sedative influence on the pneumogastric nerve, thus a better sedative in cough.
Indications for the use of Opium:
1. To relieve pain and spasm.
2. To produce sleep.
3. To abort inflammation.
4. To check excessive secretions.
5. To act as a stimulant and supporting agent.
6. As a sudorific (not so active in animals as in man).