- Lithium inhibits inositol monophosphatase and thereby lowers inositol levels and raises inositol-1-phosphate levels. Many of lithium's biological effects are reversible by inositol replacement. However, lethality caused by high dose lithium was not found to be reversible by intracerebroventricular inositol in various dosages or schedules. Moreover, inositol-1-phosphate, given alone or in the presence of sublethal Li doses to inhibit its degradation, did not show toxic or lethal effects. Therefore inositol depletion or inositol-1-phosphate accumulation are probably not related to lithium lethality.