Myocardial damage in a 4-year old who ingested bisoprolol and hydrochlorothiazide - Incidental CK-BB highlighted other tissue toxicity.

Introduction: A 4-year-old girl accidentally ingested an unknown quantity of bisoprolol (2.5 mg)-hydrochlorothiazide (6.25 mg) pills. Initialy asymptomatic, laboratory testing revealed elevated concentrations of cardiac and skeletal muscle injury markers. This case provided insight into potential myocardial toxicity and bone remodeling effects of these antihypertensive medications following acute overdose ingestion.

Materials and methods: Upon admission, the patient underwent clinical and laboratory evaluations, which included electrocardiogram (ECG), echocardiography, blood gas analysis, and assessment of biochemical markers for cardiac injury (high sensitivity troponin [hs-TnI], N-terminal pro brain natriuretic peptide [NT-proBNP]) and bone turnover (parathyroid hormone [PTH], vitamin D, bone alkaline phosphatase [bALP], beta cross-laps [CTX]). Bisoprolol was measured in plasma and urine. Creatine kinase (CK) isoenzymes were performed on agarose gel electrophoresis. Activated charcoal was administered; fluids and electrolytes were closely monitored. Clinical and laboratory follow-up continued for two months.

Results: The child's vital signs were stable, but a reduced heart rate (75 bpm) developed within 24 h. Elevated hs-TnI and NT-proBNP levels indicated myocardial stress, despite normal ECG and echocardiography findings. The CK-BB isoenzyme increased to 8 % of total CK by day 3. An increase of CTX along with decreased PTH and bALP, suggested thiazide-induced osteoclastic activation. Bisoprolol concentrations quickly decreased over 12 h. The patient was discharged in good condition after 36 h. All biomarkers normalized progressively during follow-up.

Conclusions: This case highlights subclinical myocardial toxicity and an unexpected bone remodeling after a pediatric overdose of bisoprolol-hydrochlorothiazide. CK-BB elevation, likely due to osteoclast activity, underscores the importance of monitoring skeletal biomarkers in thiazide exposures. Clinical recovery can occur before biochemical normalization, emphasizing the need for extended follow-up even in asymptomatic cases.