Endocrine Abstracts

Introduction: Interaction between diabetes mellitus (DM) and an infection usually results in hyperglycaemia. However, there is data describing hypoglycaemia events related with the association between certain antibiotics and oral anti-diabetic drugs or insulin.

Case report: Male, 73 years old, with history of hypertension, obesity and dyslipidaemia. DM type 2 was diagnosed 13 years ago with any macro or microvascular complications so far. Currently he’s treated with insulin detemir (40+28U) and vildagliptin+metformin 50/1000 2id, maintaining good metabolic control (HbA1c 6.9%) with rare episodes of hypoglycaemia. Owing to dental abscess he started a treatment with clarithromycin 500 mg bid. After 36 h of taking the drug, referred two episodes of night symptomatic hypoglycaemia, on consecutive days (42 and 37 mg/dl respectively), which reversed after sugar intake. In this context, he went to our clinic, and the antibiotic was changed to amoxicillin+clavulanic 850+125 mg, keeping the usual therapy for DM. There weren’t any more episodes of hypoglycaemia.

Conclusions: In the literature there are few reports of hypoglycaemia induced by clarithromycin in combination with insulin detemir. 40–70% of clarithromycin circulates bound to proteins, which can dissociate insulin detemir of protein binding sites (98% binds to albumin), increasing the free concentration and its pharmacological effects. This phenomenon can cause a faster beginning of action, simulating an insulin with intermediate or short-action, leading to hypoglycaemia. Clarithromycin is a potent inhibitor of CYP3A4. Vildagliptin isn’t a substract of this cytochrome. Metformin is a substract of this cytochrome’s family, but there isn’t any report of hypoglycaemia with this association.

Clinicians should be aware of this drug interaction, regarding the need of adjustments of insulin doses to avoid possible adverse effects and hospitalizations. Patients who start clarithromycin should be advised to have more frequent monitoring capillary blood glucose and re-educated about the signs, symptoms, and treatment of hypoglycaemia.