Meropenem-induced hypokalemia and metabolic alkalosis.

Sir,

A 6-year-old girl born of a non-consanguineous marriage was referred to our hospital for hypokalemia. She had cough, cold, fever and myalgia for 3 days. There was no history of loose motions, abdominal pain, dysuria, vomiting or altered sensorium. Her past, development and family history was normal. She was admitted in a private hospital and started on intravenous fluids, intravenous meropenem (60 mg/kg/day divided 8 hrly) and antipyretics. Reports of the investigations carried out in private hospital are shown in Table 1. Her fever subsided in 2 days. However, she developed hypokalemia on the fourth day and was referred to us for further management. On admission, she was afebrile and hemodynamically stable. Her general and. systemic examination was normal. She was advised admission but refused due to personal reasons. Hence she was investigated and followed up on OPD basis. Arterial blood gas analysis revealed metabolic alkalosis, serum potassium was 2.9 mEq/L and urinary chloride was 28 mEq/L. Serum calcium, magnesium, hemogram, electrocardiogram and renal function tests were normal. She was advised normal diet, meropenem was omitted and oral potassium supplements were started. Her serial investigations are shown in Table 1. After 3 days of stopping meropenem, the metabolic alkalosis and hypokalemia resolved. The Naranjo algorithm for adverse drug reaction causality assessment yielded a score of 6, suggesting that the adverse drug reaction was probably related to meropenem.[1] On follow-up after 6 months she was asymptomatic.

Table 1

Serial laboratory parameters of the patient receiving intravenous meropenem

Meropenem is a new ‘carbapenem’ antibacterial agent with a broad spectrum activity against Gram-negative, Gram-positive and anerobic organisms. It is stable against β-lactamases, human renal dehydropeptidase-I, has less epileptogenic activity than imipenam and a good cerebrospinal fluid penetrability.[2] With easy availability and broad spectrum coverage, its use has increased tremendously and hence it is essential for pediatricians to be aware of various side effects of the drug. Common adverse events include diarrhea, rash, nausea, headache, abdominal pain, vomiting and inflammation at injection site. Other reported adverse events include oral thrush, prutitus, mild elevations in hepatic enzymes, cholestasis, renal derangement and thrombocytopenia.[2] Hypokalemia and metabolic alkalosis are rare side effects reported.[3-5] β-lactam group of drugs (penicillin, carbacellin) cause hypokalemia and metabolic alkalosis by distal delivery of non-reabsorbable anion which increases K+ and H+ excretion. Meropenem causes metabolic alkalosis by the same mechanism due to structural similarities.[34] The alkalosis and hypokalemia usually resolves after 2-3 days of stopping the meropenem and is usually not associated with hemodynamic instability or any other apparent symptoms.[3] Rarely, hypokalemia may persist resulting in chronic muscle weakness.[45] This can lead to diagnostic difficulties especially in intensive care where patients are on mechanical ventilation. Persistent hypokalemia can cause difficulty in weaning the patients.[4] This case aims to highlight this rare adverse effect of meropenem. Paediatricians should be aware of and keep a vigil for hypokalemia and metabolic alkalosis in patients on meropenem therapy.