TRANQUILLIZING AND HYPOTENSIVE ACTIVITIES OF TWELVE PHENOTHIAZINES

Twelve phenothiazine derivatives have been compared in relation to their central sedative, tranquillizing and hypotensive activities. The ED50's of the compounds to suppress the conditioned response, unconditioned response and forced locomotor activity were determined. Suppressions of the conditioned and unconditioned responses were taken as criteria for tranquillizing and central sedative activities respectively. The "tranquillizing ratio" (ED50 for unconditioned response/ED50 for conditioned response) was used as the criterion of tranquillizing activity in relation to sedative activity and for purposes of comparison this ratio was assigned a value of unity for chlorpromazine. Perphenazine was the most potent drug in suppressing the conditioned and unconditioned responses whereas fluopromazine had the maximal "tranquillizing index" activity. Six compounds had great, three moderate and three mild hypotensive activity when doses of 1 mg/kg were injected intravenously into dogs. The relationship of the chemical structure to the central sedative activity is discussed.

THE EFFECT OF SOME PHENOTHIAZINE TRANQUILLIZERS ON THE OESTROUS CYCLE OF ALBINO MICE

The effects of reserpine and of nine phenothiazine compounds on the oestrous cycle of albino mice were tested. With the exception of promethazine (which is not a tranquillizer) all the phenothiazine compounds and reserpine prolonged the oestrous cycle. The mechanism by which these tranquillizers interfere with the oestrous cycle is discussed.

STUDIES ON THE HYPERGLYCAEMIA INDUCED BY CHLORPROMAZINE IN RATS

Chlorpromazine induces in rats a marked and long-lasting hyperglycaemia which (a) is more marked at low than high room temperatures, (b) is inhibited by phentolamine but not by dibenamine, and (c) is prevented by adrenalectomy, by removal of the adrenal medullae and by treatment of the rats with reserpine. Other experimental results suggest that there is a correlation between the hyperglycaemia and the hypothermia induced by chlorpromazine and by its congeners. The hyperglycaemia seems to be the result of at least two factors: an activation of the adrenergic mechanisms and an impaired peripheral utilization of glucose.

ANTI-EMETIC ACTIVITY OF PHENOTHIAZINES IN RELATION TO THEIR CHEMICAL STRUCTURE

Twelve phenothiazine derivatives have been studied for anti-emetic potency in dogs against emesis induced by apomorphine. The PD(50)s of all the compounds were determined and the activities compared with chlorpromazine hydrochloride as standard. Thioproperazine methanesulphonate was 300 times more active than chlorpromazine hydrochloride and twice as active as perphenazine sodium citrate. The anti-emetic activity of the compounds has been correlated with their chemical structure.

GASTROINTESTINAL DISTURBANCES ASSOCIATED WITH WITHDRAWAL OF ATARACTIC DRUGS

The psychological effects of abrupt withdrawal of ataractic drugs have been studied by others. Physical symptoms also occur under such circumstances and include abdominal pain, nausea and vomiting. Forty patients were divided into four groups of 10, each group receiving one of the following drugs: chlorpromazine, thioridazine, perphenazine or chlorprothixene. This medication was then suddenly withdrawn. In each of the chlorpromazine and thioridazine groups, three patients had gastrointestinal symptoms within 48 hours, lasting one to eight days. One patient on chlorprothixene, 450 mg. daily, experienced symptoms for six days. Perphenazine withdrawal produced no such symptoms. Thioridazine has little antiemetic action but perphenazine is prescribed for vomiting; hence it seems unlikely that the reported symptoms are due to a rebound action on the vomiting centre.These findings are relevant to the situation of withdrawal of ataractics prior to administration of anesthetics and to drug studies involving cross-over from an active compound to a placebo. The increasing use of ataractics suggests that this additional diagnostic possibility should be considered in the presence of obscure gastrointestinal symptoms.

THE EFFECT OF PHENOTHIAZINES ON THE ELECTROCARDIOGRAM

Thioridazine, chlorpromazine and trifluoperazine were administered to six psychiatric patients. Each was used in four dosage levels (thioridazine and chlorpromazine: 200, 400, 800 and 1200 mg. daily; trifluoperazine: 8, 16, 32, 64 mg. daily); and each increase in dosage was effected after four days of drug administration.Before the trial, twice during each drug period and before commencement of the next dose regimen, an electrocardiogram (ECG) was recorded. The findings indicated that thioridazine modifies the terminal portion (S-T segment, T and U waves) of the human ECG. A similar change occurred in three of six subjects while taking chlorpromazine and in one of six while taking trifluoperazine. Thioridazine induced changes in all six subjects studied, viz., blunting and notching of T waves with or without prolongation of QT interval. In some the notching produced a doublehump appearance in which a T wave of reduced voltage formed the proximal hump and a positive U wave of increased voltage formed the distal hump.Thioridazine-induced alterations in the ECG have been described as resembling those caused by quinidine; they also resemble changes associated with hypokalemia.

SLEEP DISTURBANCE IN DEPRESSED PATIENTS: OBJECTIVE AND SUBJECTIVE MEASURES

Complaints about lack of sleep are frequently made by patients diagnosed as depressed, and various recent studies have examined this symptom by attempting to measure sleep either objectively or subjectively. In the former approach bed movements have been recorded by Cox and Marley (1959), Hinton and Marley (1959), and Hinton (1961, 1962), while Oswald et al. (1963) have based their work on EEG changes during sleep. Since lack of sleep is essentially a personal experience, most of the objective data have been combined with subjective records, such as patients' descriptions of sleep, patients' and nurses' ratings of sleep, patients' estimates of length of sleep and nurses' observations of length of sleep. Isaacs (1957) comments that no one method used alone provides a satisfactory estimate of the hypnotic properties of drugs.