Scopolamine

SCOPOLAMINE. Scopolamine or hyoscine is a complex alkaloid closely related to atropine and having the chemical formula Ci7H.N04. It is laevorotary to polarised light but in its commercial form may be mixed with its dextrorotary isomer. Scopolamine occurs in varying proportions and is extracted from deadly nightshade, henbane, thornapple and a few other less known plants. Hyoscine hydrobromide, the official preparation of the British Pharmacopoeia, consists of transparent colourless bitter crystals, which are soluble in water and have the formula The therapeutic dose is to grain.

The chief action of scopolamine is hypnotic, a condition very similar to natural sleep being induced. This usually lasts for about six hours and the patient wakes up with an unclouded mind but may complain of thirst and dryness of the mouth and throat. In some cases a stage of excitement, giddiness and inco herent speech may precede that of sleep, and it is this uncer tainty of action which renders the drug somewhat unreliable. Some tolerance is produced of ter prolonged exhibition of scopola mine so that the dose has to be increased to have the same effect.

Administration.

Scopolamine by itself does not relieve pain, so that for anaesthetic purposes it is usually combined with morphia. Some such mixture as :—Morphine gr. mine gr. , is injected hypodermically, the scopolamine being repeated as necessary in doses of gr. 4 This "twilight sleep" method does not produce surgical anaesthesia, but has the double action of dulling pain and producing loss of memory. It is thus useful in labour, especially when the process is likely to be pro longed, as in primiparae. In these cases the initial dose should be given when the first stage is well established. The patient should then fall into a somnolent condition from which she is partially roused when each pain occurs. To obtain the best effect, the patient's ears should be plugged with cotton wool, her eyes bandaged, and the room kept perfectly quiet. The chief dis advantage in the "twilight sleep" method in labour is that the child may be born in an apnoeic condition and a considerable time may elapse before regular respiration is established. If

skilled attention is available, however, it is rare for the baby to suffer any ill effects. The action of the drug upon the f oetal heart appears to be negligible. If forceps have to be applied or any other form of instrumental delivery is necessary, an inhala tion anaesthesia will have to be administered in addition.

"Twilight sleep" can also be used as a preliminary to the various types of regional analgesia. For instance, a severe opera tion can be performed under preliminary morphine-scopolamine injection and subsequent spinal analgesia without the patient being aware that he has been moved out of bed.

Some anaesthetists also use the drugs as a preliminary to general anaesthesia, such as nitrous oxide-oxygen. This method undoubtedly lessens the apprehension of a nervous patient and has the advantage that less general anaesthetic is necessary, but it tends to depress respiration so that cyanosis and a difficult administration may ensue. The breathing may become so shal low that the requisite depth of anaesthesia is impossible to attain. The blood pressure also tends to fall, while the eye and other reflex signs which are useful in estimating the depth of anaesthesia can no longer be trusted.

Scopolamine-morphine is definitely contra-indicated in children, in severe abdominal operations and in cases of intestinal obstruc tion, as the drugs may increase the paralysis of the gut. Further more, it should not be given to patients who are known to have an idiosyncrasy for either of its constituents. For these reasons, scopolamine-morphine should not be used as a routine preliminary injection but should be reserved for selected cases.

Kerr and other

s, A Combined Textbook of Obstetrics and Gynaecology (1923) ; A. R. Cushny, Pharmacology and Therapeutics (1924) ; H. E. Boyle and C. L. Hewer, Practical Anaesthetics (1923). (C. L. H.)