[Digoxin-Josamycin: a dangerous drug interaction in children]. / Digoxine-Josamycine: une interaction dangereuse chez l'enfant.

Digitalis intoxication is usually accidental in children. We report the case of a young infant with congenital heart disease in whom the coadministration of digoxin and josamycin led to a 50% increase in the digoxin concentration, generating sinoatrial block and cardiac failure. Clinical and electrocardiographic symptoms very quickly resolved following immunotherapy with antidigitalis Fab fragments. Digoxin concentrations must be carefully monitored in patients concomitantly receiving macrolides to ensure that the digoxin dose can be readjusted if necessary.

A chronic toxicity study of josamycin in F344 rats.

The chronic toxicity of josamycin was examined in Fischer 344 (F344) rats. Groups of 10 males and 10 females were given the test compound in the diet at concentrations of 0 (control), 0.02, 0.1, 0.5 or 2.5% for 52 weeks. Daily intake of josamycin was 0, 10, 50, 260 and 1310 mg/kg body weight in males and 0, 10, 60, 290 and 1460 mg/kg body weight in females, respectively. Body weight gain was significantly (P<0.05) reduced in the male 2.5% group but no noticeable changes were found in food intake. In hematological examination, the platelet count was significantly (P<0.01) lower in the male groups given 0.02% or more of josamycin and in the 2.5% female group as compared with the control group values in a dose-dependent manner. In serum biochemical examination, blood urea nitrogen was significantly (P<0.05 and P<0.01, respectively) higher in males given 0.5 and 2.5% and total bilirubin was significantly (P<0.05) higher in females receiving 2.5% as compared with those of the control group. No death occurred at any dose levels during the dosing period. At necropsy, with the exception of cecal enlargement in the groups given more than 0.1% josamysin and a significant (P<0.01) increase in the relative liver weight of females in the 2.5% group, no particular findings related to the administration were observed. Histopathologically, the incidence and severity of liver bile duct proliferation in female 2.5% group were significantly (P<0.01) greater than those of the control group. Other histological changes found in the treated and control groups were similar to the spontaneous lesions in this strain of rats in terms of the incidence and severity. Interestingly, the josamycin treatment reduced the development of altered liver cell foci in females in a dose-dependent manner. Thus, it is concluded that, under the present experimental conditions, josamycin induces bile duct proliferation in female F344 rats at a high dose of 1460 mg/kg body weight. Based on the decrease of platelet count found in males given 10 mg/kg body weight or more, the no-observed-adverse-effect level (NOAEL) was estimated to be less than 10 mg/kg body weight.

Suppressive effects of josamycin on the development of altered liver cell foci and chronic nephropathy in a carcinogenicity study.

The carcinogenicity of josamycin was examined in Fischer 344 (F344) rats. Groups of 50 males and 50 females were given the compound in their diet at concentrations of 0 (control), 1.25 or 2.5% for 104-weeks; these dose levels were selected on the basis of the results of a subchronic study, in which animals rather rejected 5% josamycin. All surviving rats were killed at wk 106. A variety of tumours developed in all groups, including the control group, but all the neoplastic lesions were histologically similar to those known to occur spontaneously in this strain of rats, and no statistically significant increase in the incidence of any tumour was found in the treated groups of either sex. Interestingly, the josamycin treatment significantly reduced the development of altered liver cell foci and chronic nephropathy in a dose-dependent manner. Thus, it was concluded that, under the present experimental conditions, josamycin is not carcinogenic in F344 rats.

[A 13-week subchronic toxicity study of josamycin in F344 rats].

A 13-week subchronic toxicity study of josamycin was performed in male and female F344 rats to determine the maximum tolerable dose (MTD) for subsequent investigation of the carcinogenicity. As animals refused to take diet containing 5.0% josamycin in our preliminary study, dose levels in the present study were determined as 0, 0.16, 0.32, 0.63, 125 and 2.5% in diet. Rats were randomly allocated to 6 groups, each consisting of 10 males and 10 females. No animal died during the administration period and no group showed significant changes in body weight gain. Definite toxicity of josamycin was not noted in hematological and serum biochemical examinations. Histopathological examinations revealed no particular findings related to josamycin administration except cecal enlargement in the 1.25 and 2.5% groups. based on the results of the present study, it was concluded that the MTD of josamycin in 2.5% in diet, because the dietary dose level of 2.5% proved to exert no significant toxicological signs.