ارتباط بين نسبت ليتيومي و بروز برخي عوارض كليدي آن در بيماران ايراني مبتلا به اختلالات خلقي دو قطبي

Relationship between lithium ratio and the incidence of some renal side-effects in Iranian patients with bipolar disorder

Introduction: There are several studies about the correlation between various clinical parameters (plasma lithium concentration, lithium treatment duration and frequency of lithium administration) with lithium nephrotoxicity. In some of these studies the results are conflicting or the selected methods are expensive. Our objective was to find an accurate, available and inexpensive parameter for predicting and preventing renal side-effects of lithium. Methodss: During a case-control inpatient study the correlations between the lithium ratio (LR) and the incidence of some renal side-effects and the type of comedications were studied in 70 Iranian bipolar patients admitted at Roozbeh Mental Health Hospital by using direct method of measuring of erythrocyte lithium concentration. Blood samples were drawn 12± 0.5 hours after the last dose of lithium. The cases were patients who had urine specific gravity of 1.006 or less after 8-10 hours water deprivation at night and the controls had specific gravity of 1.011 or more after this period. Blood urea nitrogen, serum creatinine, sodium and potassium and urine pH, sodium and potassium were measured in all patients at this time. Renal indices were compared by using independent sample t-test at a significance level of a Pvalue of 0.05 or less. Pearson rank correlation test was used to investigate the relationship between clinical variables and the indices of renal function. Results: Results revealed that in case group mean serum sodium concentrations were significantly higher (P=0.008) and mean urine sodium and potassium were significantly lower than that of controls (P-0.004, P=0.007 respectively). We found no statistically significant difference in LRs between two groups. However, erythrocyte lithium concentrations were significantly higher in cases (P=0.026). There were no significant correlation between concomitant use of neuroleptics or benzodiazepine and LR or lithium renal side effects. Conclusion: This study showed that erythrocyte lithium concentration may be a better predictor of lithium nephrotoxicity than its plasma concentration and LR.