The element lithium is used as its carbonate salt as the medication of choice for treatment of Bipolar Disorder.
Lithium carbonate has a low therapeutic ratio, that is to say, the standard effective dose is close to the toxic dose. Consequently, the dose must be tailored to the patient by monitoring blood levels of lithium every two to three days during initiation and stabilisation of the therapy, and every six to twelve weeks when stable.
However, onset or deterioration of other illnesses, major surgery, dehydration and various medications1 [], may destabilise therapy, and require a return to frequent monitoring of blood levels of lithium until stable once again.
PRACTICE POINT Drugs that may cause lithium toxicity: 1. ACE inhibitors 2. NonSteroidal Anti-Inflammatory Drugs (NSAIDs) 3. Antipsychotic drugs 4. Anti-epileptic drugs 5. Calcium antagonists 6. Selective Serotonin Reuptake Inhibitors (SSRI) |
Interaction with SSRI antidepressants2 such as Prozac (fluoxetin) is perhaps the least recognised hazard, and is particularly relevant when the drugs are used in combination to fine-tune control of Bipolar Disorder. Moreover, addition of SSRI to lithium therapy significantly increases3 the probability of polyuria, which has been shown to be more associated with high4, than with low, blood levels of lithium.
This wide range of drugs with which lithium may have an adverse interaction requires general and family physicians to maintain a degree of diagnostic and therapeutic sophistication and vigilance if they are prescribing lithium to patients. Mild to moderate lithium toxicity is relatively common1 [].
Viable Causes of medical malpractice Action generally arise out of a) failure to monitor closely during such destabilising events or b) failure to recognise the symptoms of lithium toxicity.
Vomiting and diarrhea commonly accompany the onset of therapy and are unreliable indicators of toxicity. Toxic symptoms, including death, may arise from compromised function of kidneys, heart and central nervous system.
The elderly are particularly vulnerable5 and can develop serious adverse effects while taking lower doses and at lower blood levels of lithium. Both age-related decreases in brain, heart and kidney function, and an increased prevalence of diseases, compound the difficulty of prescribing safely for ageing patients1 [].