This section is from the "A Handbook of Useful Drugs" book, by State Medical Examining and Licensing Boards.
An alkaloid obtained from opium, the chief therapeutic constituent of the drug.
Properties : Morphin occurs as colorless or white crystals or a crystalline powder, odorless and having a bitter taste. It is very slightly soluble in water (1:3,300), but slightly soluble in alcohol (1:168).
Incompatibilities: Morphin solutions are incompatible with alkalies, tannic acid, iodids and other precipitants of alkaloids.
Action and Uses: There are essentially three actions of morphin: a specific central analgetic action, a depressant action on the entire central nervous system, of a descending type, and a constipating effect resulting from a combination of central and local actions.
Morphin is practically devoid of local action, except on the gastro-intestinal tract. This local action is the subject of much debate, but it seems certain that it plays a part in the causation of the constipation which results from the administration of the drug. The drug has no local analgetic action and its use locally for the relief of pain is irrational.
The systemic actions of morphin are greatly dependent on the dose used. The smallest doses producing therapeutic effects result in the relief of pain; somewhat larger doses cause definite cerebral depression leading to more or less profound and prolonged sleep.
Some persons react peculiarly to morphin, showing one or more of the following symptoms: Cerebral excitation is, perhaps, more common in women than in men, but it is usually mild and of short duration, soon giving place to the depressant action of the drug. Nausea and even vomiting not infrequently result from the systemic administration of a small dose. In some persons nausea is a very pronounced after-effect of the drug, lasting, at times, for hours.
The drug probably exerts a decided effect on the heart, through the vagus mechanism, chiefly influencing the rhythm, which may become irregular. The rate may be slowed considerably after large doses, but morphin does not endanger life through its cardiac action.
Morphin causes a marked constriction of the pupil when given in moderate doses, and this phenomenon is often used as a gage for the cessation of its administration in cases in which large doses are necessary. It has no local miotic action when dropped into the eyes.
The respiratory center is depressed by relatively small doses of morphin—Such as are too small to be hypnotic. Use is made of this action in the treatment of persistent and troublesome cough, but it should be remembered that if the cough is "productive," the depression of the cough reflex may lead to a dangerous retention of the secretions of the inflamed mucosa.
Morphin is used chiefly as an analgetic in conditions of severe acute pain, and its use should be very guarded on account of the great danger of the formation of the morphin habit. In surgical conditions in which the alleviation of severe pain may obscure the course of the disease and lead to the unwarranted postponement of an operation, morphin should not be used, or only in very small doses and with circumspection. In chronic conditions associated with pain morphin should not be used, as the formation of the habit is almost certain to result from its prolonged administration. Exceptions to this generalization are to be found in such conditions as inoperable cancer, etc., in which the condition is hopeless and at the same time the cause of much suffering. Morphin should not be used for the relief of pain in persons of a neurotic or hysteric temperament, unless absolutely unavoidable. In general, it may be said that morphin should not be used for the relief of pain when any satisfactory relief can be obtained by the use of other drugs. Morphin, in moderate doses, is very useful in pain of cardiac origin. Morphin may be used to relieve the attacks of asthma and to lessen dyspnea from other causes, but caution should be exercised that the slowing of the respiration does not embarrass the heart. It should be used cautiously in the pain and dyspnea of uremia, as it interferes with elimination by the kidney and bowel.
Since the introduction of the coal-tar hypnotics and those of the chloral group, the use of morphin as a pure hypnotic has become exceptional.
Morphin, in the form of opium, is often given as a diaphoretic, the well-known Dover's powder being the preparation commonly used
Habituation to morphin is readily established, and this habit is one of the most difficult to break. The indiscriminate use of morphin and preparations containing it by physicians is a common cause of the habit, and too great discrimination in its use can hardly be urged.
Overdoses of morphin lead to intoxication which may result fatally. The symptoms begin with the usual depression which deepens into sleep. The pupils become extremely constricted. Respiration becomes slow; the sleep deepens into coma from which the patient can be aroused with difficulty at first; later he cannot be aroused at all, and the respiration sinks to as low as three or four per minute. The heart is somewhat weakened and its rate is slowed. Death results from respiratory failure.
The treatment of morphin poisoning is not germane to this work, but its proper execution will often save a patient who is deemed hopeless.
Morphin is excreted largely through the alimentary tract, including the stomach. Some of the morphin thus excreted may be reabsorbed into the circulation; hence, in cases of poisoning, the use of frequent gastric lavage with permanganate of potassium, to destroy the morphin, is an important measure. Even after the hypodermic administration of the drug it is excreted by way of the gastro-intestinal tract.
Morphin is also used to lessen secretion and check peristalsis in diarrhea. For this purpose opium appears to be more efficient than morphin.
In the administration of morphin the danger of forming a habit should never be forgotten.
Dosage: 0.01 gm. or 1/6 grain. Smaller doses from 0.005 to 0.008, 1/12 to 1/8 grain, are often sufficient. The minimum fatal dose is 0.06 gm. or 1 grain.
Properties : Morphin hydrochlorid occurs as white crystals or as a crystalline powder, odorless and having a bitter taste. It is soluble in water (1 :17) and in alcohol (1 :42).
Dosage: 0.01 gm. or 1/6 grain.
Properties : Morphin sulphate occurs as white, feathery crystals or in cubical masses, odorless, permanent in the air and having a bitter taste. It is soluble in water (1 :15.3), but only slightly soluble in alcohol (1:465).
Dosage: 0.01 gm. or 1/6 grain.