The inhibitory effect of aureomycin (chlortetracycline) pretreatment on some rat liver microsomal enzyme activities

[Effects of oxytetracycline on rat liver]

OBJECTIVES

This experimental project was designed to evaluate: a) the capacity of oxytetracycline to induce microvesicle steatosis in rat liver when administered over long time periods; b) whether female rats are more susceptible to this substance, and c) the possible ultrastructural alterations and their relation to the mechanisms of steatosis.

METHODS

Sixty-two Wistar rats (31 males and 31 females) were distributed into six groups, two control groups and four experimental groups. The experiment lasted three months. Blood and hepatic tissue samples were extracted under anesthesia for morphologic study (optical and electron microscopy).

RESULTS

Steatosis was of the microvesicular type with mainly periportal distribution. Steatosis developed in the treated groups and the degree was significantly greater in the females (p = 0.004). No relationship was found with dose. Ultrastructural study revealed microsome dilation in all experimental groups, with no differences according to sex. Despite the steatosis, no proliferation of peroxisomes or mitochondrial alterations were observed.

CONCLUSIONS

Oxytetracycline produced predominantly periportal microvesicular hepatic steatosis, appearing mostly in the females. As a possible mechanism for tetracycline-induced steatosis, we postulate a decrease in mitochondrial, peroxisome and microsome function as a result of protein synthesis inhibition in these cell compartments.

Enhanced anticoagulant effect of coumarin derivatives induced by doxycycline coadministration

OBJECTIVE

To report two cases of enhanced oral anticoagulant effect induced by doxycycline coadministration.

DESIGN

Case report.

SETTING

University teaching hospital.

PATIENTS

Two patients on chronic oral anticoagulation therapy who presented with severe bleeding and marked impairment in blood coagulation tests shortly after the initiation of doxycycline therapy.

DISCUSSION

The literature concerning the possible effects of tetracyclines on hemostasis with or without antecedent anticoagulation therapy is reviewed and the speculated mechanisms for such an interaction are discussed.

CONCLUSIONS

The administration of tetracyclines such as doxycycline to patients on chronic oral anticoagulation therapy may be associated with a marked enhancement in anticoagulant effect. In such patients the prothrombin ratio should be closely monitored and the anticoagulant dosage adjusted accordingly.