INHIBITION OF DRUG METABOLISM BY CHLORAMPHENICOL

1397

between the end of normal and the beginning of abnormal is to understand the mechanisms of adaptation, and in particular by identifying those properties or characteristics which the body tries to maintain constant at the expense of others ". He has described an adaptation to low-protein intake by a diversion of metabolic pathways resulting in a greater proportion of available nitrogen being used for protein synthesis, and a lesser proportion being excreted than normally. Other workers have reported other adaptive mechaA Chilean group have nisms during marasmus. reported a reduction in the mitotic index of the jejunal mucosa in marasmic children.7 They feel that these changes may be mediated by a reduction in growth hormone and thyroid-stimulating hormone.8 We believe that our results indicate another physiological adaptation to chronic insufficient calorie and protein intake by a complete shift to the resting phase of hair-growth. This re-establishment of priorities reduces the amount of nitrogen loss that would other-

tinguish

wise

occur

if the

roots

remained in the

growing

phase. We do not mean to imply that the different results obtained for the two classical extreme conditions can be used diagnostically across the wide, unordered spectrum of infantile malnutrition, particularly when the vast majority of cases are intermediary in nature and classification. We do feel, however, that the different results found in the two clearly defined extremes of protein-calorie malnutrition are attributable to somewhat different types of stress on the hairfollicle. The differences are more probably due to comparative differences in chronicity than to specific differences in relative protein-calorie density. Classical marasmus is a severe chronic undernutrition in which the child adapts to the stress by failing to grow. The long-term effect on the hair-follicle is that it shifts to the resting phase and conserves nitrogen. In classical kwashiorkor there has been a period of more normal growth which has been interrupted by an acute condition. Linear growth may continue as the hair-follicle adapts to this stress by both atrophy of bulbs already in the growing phase and a partial shift to the resting phase. The fact that defensive physiological adaptations to the calorie and protein stress of marasmus also take place in hair-roots is of particular interest because hair is a readily accessible tissue which also has the unique advantage of reflecting not only present conditions but also the recent past through a combination of linear growth, toughness, and slow rate of destruction. This work was supported by grants from the Human Nutrition Research Unit, U.S. Dept. of Agriculture; the Rockefeller

defy tidy

Foundation; the Center for Latin American Studies of University of California; and by N.I.H. (AM09980).

the

REFERENCES 1.

Bradfield,

R. B. in Calorie Deficiencies and Protein Deficiencies by R. A. McCance and E. M. Widdowson); p. 213.

(edited London, 1968. 2. Bradfield, R. B., Bailey, M., Margen, S. Science, N.Y. 1968, 157, 438. 3. 4. 5. 6.

Bradfield, R. B., Bailey, M., Cordano, A. Lancet, 1968, ii, 1169. McLaren, D. S. ibid. 1966, i, 485. Maguire, H. C., Kligman, A. M. J. invest. Derm. 1964, 43, 77. Waterlow, J. C. Lancet, 1968, ii, 1091. 7. Brunser, O., Reid, A., Mönckeberg, F., Maccioni, A., Contreras, I. Pediatrics, Springfield, 1966, 38, 605. 8. Mönckeberg, F., Donoso, G., Oxman, S., Park, N., Meneghello, J. ibid. 1963, 31, 58.

INHIBITION OF DRUG METABOLISM BY

CHLORAMPHENICOL L. KORSGAARD CHRISTENSEN

L. SKOVSTED

Medical Department F, Gentofte Copenhagen, Denmark

Hospital,

Chloramphenicol has been shown to Summary retard the biotransformation of tolbutamide, diphenylhydantoin, and dicoumarol in man. Treatment with 2 g. of chloramphenicol for some days resulted in a rise in the concentration of tolbutamide and diphenylhydantoin in blood. The half-life values of tolbutamide, diphenylhydantoin, and dicoumarol in blood increased very considerably after chloramphenicol. A case of chloramphenicol-induced hypoglycæmic collapse in a tolbutamide-treated patient is

reported. Introduction

THE stimulatory effect of some drugs on liver microsomal enzyme activity has long been recognised. This effect may accelerate the biotransformation of other drugs and shorten the intensity and duration of their action.1 However, the opposite effect-retardation of the metabolism of one drug by another-may also have important clinical implications. Sulphaphenazole, phenylbutazone, and dicoumarol inhibit the metabolism of tolbutamide and diphenylhydantoin (phenytoin) and may cause intoxication by these drugs.2-4 The increase in serum-diphenylhydantoin induced by disulfiram5 or sulthiame6 are other

examples of this type of drug interaction. Clinical observation suggested to us that some of the broad-spectrum antibiotics might also be inhibitors of drug metabolism; and we have tested this idea by looking at the metabolic transformation of tolbutamide, diphenylhydantoin, and dicoumarol in patients given chloramphenicol. Methods Serum-tolbutamide was estimated by the method of Spingler.The serum half-life of tolbutamide was determined after giving tolbutamide 0.75 g. intravenously. Blood-samples were drawn at 11/2 hours intervals for the next 12 hours. Thin-layer chromatography was used to ascertain that the compound measured by the Spingler procedure was tolbutamide and not its hydroxymethyl or carboxy derivative. Serum-diphenylhydantoin was measured by the method described by Dill et al. 8 The half-life of diphenylhydantoin in blood was determined by giving an intravenous injection of 100 mg. of diphenylhydantoin to which 20 µCi 4-[14C]diphenylhydantoin had been added. Radioactivity was measured in extracts of serum from blood-samples taken at 3-hour intervals for the next 12 hours. We used thinlayer chromatography to confirm that all the radioactivity was in the diphenylhydantoin spot. The half-life of dicoumarol in plasma was determined by giving an intravenous dose of 50 mg. dicoumarol containing 20 µCi dicoumarol labelled with 14C at the methylene bridge and measuring radioactivity in extracts of plasma from blood-samples taken over a period of 5-60 hours after the injection. Thin-layer chromatography was again used to confirm that all the radioactivity was in the dicoumarol spot.

All

the

figures given

determinations.

are

the

means

of

two

1398 Results Chloramphenicol-tolbutamide Interaction

Three patients were given tolbutamide 500 mg. three times a day at equidistant intervals. After 4 days, serum-tolbutamide determinations were started, blood-samples being taken 2 hours after the morning dose. After adding chloramphenicol (2 g. daily) to the regimen, the serum-tolbutamide rose to about double the pre-chloramphenicol level in all three patients. One of the cases is shown in fig. 1. Tolbutamide half-lives were prolonged in another three patients (see table) after they had had chloramphenicol (2 g. daily) for about 10 days. An intravenous dose of 3 g. of chloramphenicol (administered as succinate) resulted in a rapid change of the slope of the serumtolbutamide curve corresponding to a change in halflife from 5 to 83/4 hours (fig. 2). In another patient an intravenous dose of 1-5 g. chloramphenicol caused a change in half-life from 43/4 to 7 hours.

Fig. 2-Change in blood half-lives of tolbutamide and

diphenylhydantoin after chloramphenicol.

sugar values around 50-60 mg. per 100 ml.

(Hagedorn’s

found despite repeated glucose injections. After 24 hours he had recovered completely. Besides chloramphenicol and tolbutamide he had been given chlorhexadol 800 mg. every evening for about a month. The concentration of tolbutamide in serum from a bloodsample drawn 10 hours after the last dose of tolbutamide was 9-6 mg. per 100 ml. Normally a value of about 2-3 mg. per 100 ml. would have been expected. The blood-level was found to decrease corresponding to a half-life of tolbutamide of about 10 hours. Since the patient participated in a special study (see above), the tolbutamide halflife had been measured before any chloramphenicol or tolbutamide medication. It was about 4 hours. At this time the patient got no other drug than the chlorhexadol mentioned above. With the above experiments in mind, it seems

method)

were

reasonable to consider this hypoglycaemic episode to be due to a chloramphenicol-tolbutamide interaction. The chlorhexadol is not likely to have been important because the tolbutamide half-life was only 4 hours when this sedative was given as the only drug.

Fig. 1—Chlorampheniecol-induced rise in serum-tolbutamide and serum-diphenylhydantoin (single cases).

Colleagues drew our attention to the following of hypoglycxmic coma in a patient participating

case

in a controlled trial of tolbutamide in Parkinson’s disease in 1964.9 A 76-year-old man was admitted to hospital on July 25, 1964, for treatment of Parkinson’s disease. He had had intermittent pyuria for several years, and this had been treated with chemotherapeutic agents and antibiotics. Because urinary infection with fever recurred, chlor-

amphenicol (0-5 g. four times a day) was given from Aug. 21. the effect of tolbutamide on Parkinson’s disease, he was started on tolbutamide (0-5 g. four times 22 Aug. a day). On the morning of Aug. 25, he had a typical hypoglycaemic collapse, which responded to the intravenous injection of 30 ml. of 50% glucose in water. The blood-sugar was not determined before the injection of glucose. During the next 20 hours, however, several blood-

To

on

test

Chloramphenicol-diphenylhydantoin Interaction Diphenylhydantoin (250 mg. a day) was administered to two patients. After the drug had been given for 4 days, blood for determination of serum-diphenylhydantoin was drawn every day (3 hours- after the morning dose). When chloramphenicol (2 g. a day) HALF-LIVES OF

TOLBUTAMIDE, DIPHENYLHYDANTOIN, AND DICOUMAROL IN BLOOD

1399

considerable rise in the serumlevels was observed in both patients. diphenylhydantoin One of the cases is illustrated in fig. 1. The half-life of diphenylhydantoin was determined in three other patients before and after administration of chloramphenicol (2 g. a day) and a considerable increase was found (see table). A single i.v. dose of 3 g. chloramphenicol caused a change of the slope of the blood radioactivity curve corresponding to a change in halflife from 10-5 to 22 hours (fig. 2). In another patient an i.v. dose of 1-5 g. caused a change from 9 to 121/2 hours.

phenicol,13 but since the retarding effect develops shortly after a single intravenous dose of chloramphenicol (fig. 2) the effect is not likely to be caused by interference with the synthesis of drug-metabolising enzyme proteins. Chloramphenicol may well inhibit the biotransformation in man of drugs other than those investigated by us. Consequently, this antibiotic should be given with a great deal of caution to patients who are treated with other medicaments, and its use should be restricted as much as possible.

Chloramphenicol-dicoumarol Interaction

This work was supported by a grant from the Arvid Nilsson Foundation, Copenhagen. Requests for reprints should be addressed to L. K. C.

was

also given,

a

The half-life of dicoumarol in blood was estimated in four patients before and after administration of chloramphenicol (2 g. a day). In all four cases the

half-life increased strikingly (see table). Discussion

We have found that chloramphenicol retards the metabolic transformation of tolbutamide, diphenylhydantoin, and dicoumarol in man. In one case hypoglycaemic coma can be explained by the simultaneous administration of tolbutamide and chloramphenicol. Other reported cases of hypoglycaemic coma may possibly also be explained by this combination of drugs. For example, Soeldner and Steinke 10 reported hypoglycaemic coma in two patients, and suggested that this might have been the result of tolbutamide-sulfisoxazole interaction; however, one of their patients was also receiving,chloramphenicol. To our knowledge no case of chloramphenicolinduced diphenylhydantoin intoxication has been recognised. The interference of chloramphenicol with diphenylhydantoin metabolism is, however, so pronounced that such intoxication might easily develop in patients getting this combination of drugs. The risk of giving broad-spectrum antibiotics to patients treated with dicoumarol is well known. The main cause of this is supposed to be a suppression of the vitamin-K1- producing bacterial flora in the gut. As far as treatment with chloramphenicol is concerned, an additional effect seems possible-namely, bleeding caused by the inhibition of dicoumarol metabolism. Dixon and Fouts 11 have shown that chloramphenicol decreases the rate of metabolic transformation of hexobarbitone, acetanilide, codeine, and aminopyrine in mice. In-vitro experiments demonstrated an inhibitory effect of non-competitive nature on the microsomal drug-metabolising enzyme system from the livers of mice. The mechanism of action was not elucidated in detail. Peters and Fouts 12 have shown that chlortetracycline inhibits liver microsomal enzyme activity. They suggest that this effect may be due to an inhibition of microsomal protein synthesis. Our experiments have shown that chloramphenicol causes an accumulation of unchanged tolbutamide and diphenylhydantoin in blood. Similarly chloramcauses an increase in the half-life values of phenicol and tolbutamide, diphenylhydantoin, dicoumarol, in blood. This effect cannot be due to a change of the renal excretion of these three drugs since none of them are excreted in the unmetabolised form to any considerable extent. The most reasonable explanation is that chloramphenicol inhibits microsomal enzyme activity in man. Protein synthesis can be inhibited by chloram-

REFERENCES

Conney, A. H. Pharmacl. Rev. 1967, 19, 317. Christensen, L. K., Hansen, J. M., Kristensen, M. Lancet, 1963, ii, 1298. 3. Hansen, J. M., Kristensen, M., Skovsted, L., Christensen, L. K. ibid. 1966, 265. 4. Kristensen, M., Hansen, J. M. Diabetes, 1967, 16, 211. 5. Olesen, O. V. Acta pharmac. Copenh. 1966, 24, 317. 6. Hansen, J. M., Kristensen, M., Skovsted, L. Epilepsia, 1968, 9, 17. 7. Spingler, H. Klin. Wschr. 1957, 35, 533. 8. Dill, W. A., Kazenko, A., Wolf, L. M., Glazko, A. J. J. Pharmac. exp. Ther. 1956, 118, 270. 9. Hansen, J. M., Kristensen, M. Dan. med. Bull. 1965, 12, 181. 10. Soeldner, J. S., Steinke, J. J. Am. med. Ass. 1965, 193, 398. 11. Dixon, L. D., Fouts, J. R. Biochem. Pharmac. 1962, 11, 715. 12. Peters, M. A., Fouts, J. R. ibid. 1969, 18, 1511. 13. Weisberger, A. S. in A Symposium on the Interaction of Drugs and Subcellular Components in Animal Cells (edited by P. N. Campbell); p. 133. London, 1968. 1. 2.

AMENORRHŒA AND GALACTORRHŒA ASSOCIATED WITH HYPOTHYROIDISM P. F. C. BAYLISS* Metabolic

W. VAN’T HOFF

Unit, North Staffordshire Royal Infirmary, Stoke-on-Trent, Staffs.

woman had persisting amenorrhœa and galacpost-partum with torrhœa associated primary hypothyroidism. The amenorrhœa and galactorrhœa both improved after treatment with thyroxine. A possible mechanism for the disorder is discussed.

Sum ary

A

26-year-old

Introduction

THE combination of amenorrhoea and galactorrhoea physiological during pregnancy and in the puerperium, but when they are prolonged beyond the normal limits of the puerperium they are considered pathological. Apart from their occasional occurrence together in acromegaly, and in a number of other situations, three more or less well-defined syndromes have been described. These are the Chiari-Frommel syndrome (persistent post-partum amenorrhoea and galactorrhoea, with atrophy of the ovaries and uterus); the del Castillo syndrome (amenorrhoea and galactorrhoea in nulliparous patients, with no evidence of a pituitary tumour and a low urinary gonadotrophin excretion); and the Forbes-Albright syndrome (amenorrhoea and galactorrhoea in non-acromegalic patients with a pituitary tumour). In 1960 a fourth syndrome of amenorrhoea and galactorrhoea associated with primary hypothyroidism was described by

is

*

Present address: Clinical Research Department, I.C.I. Pharmaceuticals Division, Alderley Park, Cheshire, SU10 4TG.