Lithium and neuroleptic drugs in combination - effect on lithium RBC/plasma ratio

The lithium RBC/plasma ratio was determined in 59 patients during prophylactic lithium therapy. No relationship was found between the lithium RBC/plasma ratio and sex, age, type of illness, weight, lithium dosage, duration of treatment or lithium plasma level. However, patients taking a combination of lithium and neuroleptic drugs had significantly higher lithium RBC/plasma ratios than patients taking lithium without neuroleptic drugs. The results are in line with earlier in vitro studies and are discussed in relation to the high frequency of neurotoxic and nephrotoxic adverse effects noted in patients taking a combination of lithium and neuroleptic drugs.