Prevalence of disturbance in calcium metabolism among paediatric patients on longterm anticonvulsants at Moi Teaching and Referral Hospital Eldoret, Kenya

Abstract

Background: Epilepsy is the most prevalent neurological disorder in children. Treatment of epilepsy involves the use of anticonvulsant drugs over a long duration with the aim of remission or when not possible, a reduction in the frequency of seizures. Anticonvulsant medications are associated with undesirable side effects that may be life-threatening or interfere with function. Disturbance in calcium metabolism leading to hypocalcaemia is one of the side effects of anticonvulsants, especially cytochrome p450 inducers which may eventually lead to break-through seizures or predispose to fractures. There is no local data on the prevalence of hypocalcaemia or consensus on the need for testing of calcium levels among children on anticonvulsant drugs. This study aims to describe the magnitude of hypocalcaemia among children on anticonvulsants drugs in our local population. Objective: To determine the prevalence and factors associated with derangement in calcium metabolism among children on chronic anticonvulsant drugs attending the neurology clinic at Moi Teaching and Referral Hospital. Methods: This was a cross-sectional study conducted over nine months at MTRH paediatric neurology clinic. Consecutive sampling was done and children aged six months to 14 years who had been on anticonvulsants for at least six months were recruited. Data on the socio-demographic and clinical characteristics of the participants was collected using an interviewer guided questionnaire. Venous blood was analysed for calcium, phosphate, and alkaline phosphatase levels, which were considered markers for calcium metabolism. The prevalence of derangements in calcium metabolism was presented using frequency distribution. Chi-square and Fischer's test were used to test for associations, and all analysis was at 95% CI. Results: A total of 98 patients were recruited with a male: female ratio of 1.2:1 and a median age of 8yrs (IQR 4, 11). The most common type of epilepsy was generalized tonic-clonic seizures at 38.8 %. Length of anticonvulsive therapy ranged from 6-96 months, mean 17.6 months (SD 16.9) with 56% of the patients being on monotherapy. Hypocalcaemia, hypophosphataemia, and raised alkaline phosphatase were found in 13.3%, 12%, and 35% respectively. However, none of the patients had combined derangements in all three parameters. There was no significant association between demographic and clinical factors with hypocalcaemia; gender (P=0.306), duration of anticonvulsants use (P=0.64) and use of enzyme-inducing anticonvulsant drugs (P=0.533). There was no significant association of hypophosphatemia with; gender (P=0.65), duration of AED use (P=0.507) or use of enzyme-inducing anticonvulsant drugs (P=0.055). Conclusion: The study found a tenth of children with hypocalcemia and hypophosphatemia while 1/3 had raised alkaline phospatase. Calcium metabolism disturbance was not significantly associated with the clinical factors of the epileptic children enrolled in the study. Recommendations: Future studies that are larger with more drug representation to establish their influence on calcium and any associated factors