Conium

Hemlock. The full-grown fruit of Conium maculatum Linné (Nat. Ord. Umbelliferae), gathered while yet green. Ciguë, Fr.; Schierling, Ger.

Extractum Conii Alcoholicum

Alcoholic extract of conium. Dose, gr. j—gr. v.

Extractum Conii Fluidum

Fluid extract of conium. Dose, τη ij--τη v—τη Xl.

Tinctura Conii

Tincture of conium. Dose, τη x— 3 j. (Not official.)

The preparations of conium are very uncertain in strength. It is pretty well established that the extracts are nearly, if not quite, inert. The best preparations are the fluid extract and. alkaloid.

Composition

The special powers of hemlock are due to a peculiar alkaloid (conine). This is an oily, limpid liquid, having a strong alkaline reaction, a peculiar odor resembling the urine of mice, and a specific gravity of 0·88. It probably exists in the plant in the form of the malate; but, by some authorities, the acid with which it is combined is supposed to be an acid peculiar to conium, the coneic acid. Conine is associated with ammonia, and another crystallizable alkaloid, conhydrine.

Conine is quickly decomposed by heat. Exposed to the air, it is soon converted into a brownish resin, and becomes inert. Hence it is that the preparations of conium possess but little activity, and are so frequently, indeed entirely, wanting in physiological and therapeutical effects. It is better, therefore, to administer the alkaloid, which, being soluble in alcohol, may be administered in that menstruum, or it may be converted into an acetate and dissolved in a mixture of alcohol and water. It is to be noted, also, that different specimens of conine differ remarkably in activity; hence, whenever a new preparation is begun, the minimum dose should be first administered until its real power is ascertained (Burman).

Conine

Dose, gr. -1/60—gr. 1/20—gr. 1/10, or in minim-doses from τη1/10 —τη ij. Half a minim of conine (pure) is about equivalent in activity to oz j of the best succus conii. The chlorhydrate and especially bromhydrate of conine are greatly to be preferred, not only to the pure alkaloid, but to any of the preparations of conium. The bromhydrate crystallizes in the form of colorless, prismatic needles, which are freely soluble in water and also in alcohol, have but little taste, and no odor (Mourrut). The dose of this salt ranges from 1/12 of a grain to ¼, ½, even 1 grain. It is not actively toxic. By reason of this fact, its freedom from a disagreeable taste or odor, and its solubility, the bromhydrate is a most desirable preparation for administration, either by the stomach or hypodermatically.

Antagonists and Incompatibles

The caustic alkalies and tannic acid are chemically incompatible. Physiologically considered, the actions of conium are antagonized by nux-vomica and its alkaloids strychnine and brucine, by picrotoxin, and the tetanizing agents in general.

Synergists

Gelsemium, tobacco, veratrum viride, aconite, me-thyl-strychnium, hydrocyanic acid, and curara, increase the action of conium.

Physiological Actions

The preparations of conium possess a considerable degree of acridity, and are therefore apt to produce gastric irritation, nausea, and vomiting. These results sometimes follow the subcutaneous injection of conine. The active principles readily diffuse into the blood. What changes, if any, they induce in the blood are quite unknown. It is probable that they limit the power of the red blood-globules to convey oxygen to the tissues on which they have a selective action—the motor nerves.

When an active dose of conine is administered, weakness of the legs and a sense of weight and fatigue of these members are first experienced. The eyelids become heavy and droop somewhat, and double vision, or confused vision, a feeling of torpor of the mind, and giddiness, follow. Speech is also affected as respects vocal utterance, but the memory for words and the faculties of mind generally are unimpaired. When the dose is a lethal one, paralysis of the voluntary muscles—first of the inferior extremities—ensues; there is considerable vertigo, the mind is torpid and indifferent but not perverted, speech and vision are lost, the respiration becomes labored and slow from paralysis of the respiratory muscles, and death occurs from asphyxia, the action of the heart continuing until after respiration has ceased. The mind remains unclouded to the last, except when delirium ensues from carbonic-acid poisoning. Convulsive movements generally occur in animals from retention of carbonic acid in the blood, and in man sometimes local convulsive movements. Sensation is unaffected until near the close, but a subjective sense of numbness is experienced in the feet and legs, without actual impairment of the functions of the sensory nerves. The body temperature is decidedly lowered, and in a direct ratio to the amount of the paralysis.

The physiological effects of conine, even when produced by decidedly large medicinal doses, are hindered if not entirely prevented by active exercise. When the muscular weakness, the heaviness and sense of fatigue in the legs are first experienced, if resisted and muscular movements are carried on, these sensations disappear, and the whole duration of the physiological effects is much shortened.