LITHIUM Flashcards
What is lithium most commonly used for?
It is a mood stabilising drug that is used most commonly prophylactically in bipolar disorder but also as an adjunct in refractory depression.
What are the proposed mechanisms of action for lithium in mood-stabilisation?
Interferes with inositol triphosphate formation
Interferes with cAMP formation
How is lithium excreted?
Via the kidneys
What is therapeutic window for lithium?
Very narrow, hence why it is such a toxic drug that needs such close monitoring. Range is 0.4 - 1.0 mmol/L. It also has a very long plasma half-life.
What can affect lithium clearance from the body and lead to a build up of lithium to toxic levels?
Renal impairment
Sodium depletion - the kidney will hold onto lithium in place of sodium
Diuretics especially bendroflumethiazide
NSAIDs
ACE-inhibitors
Antipsychotics can synergistically increase lithium induced neurotoxicity
What are the side effects of lithium?
Polydipsia
Polyuria
Nausea/vomiting
Diarrhoea
Weight gain
Oedema
Fine tremor
Muscle weakness
Problems with concentration and memory
What are the complications of lithium therapy?
Nephrogenic diabetes insipidus
Thyroid enlargement, may lead to hypothyroidism
Precipitates skin problems eg psoriasis
Leucocytosis
Teratogenicity - Ebstein’s anomaly
Exacerbate myasthenia gravis
What are the clinical features of lithium toxicity?
Polydipsia
Polyuria
Coarse tremor
Hyperreflexia
Acute confusion
Seizure
Coma
What are the ECG changes associated with lithium toxicity?
T-wave flattening or inversion
How do we manage someone with mild-moderate lithium toxicity?
May respond to fluid resuscitation
How do we manage someone with severe lithium toxicity?
Haemodialysis
Sodium bicarbonate is sometimes used but there is limited evidence to support this. By increasing the alkalinity of the urine it promotes lithium excretion.
In which patients in lithium therapy contraindicated?
Breast feeding mothers
Relative contraindication for those on antipsychotics, NSAIDs, diuretics (bendroflumethiazide) and cardioactive drugs.
How are lithium levels monitored and what is the desired range?
Should be checked weekly until stable for 4 weeks and every 3 months thereafter
Levels taken 12 hours post-dose
Range should be 0.4 - 1.0 mmol/L
Patients should be issued with an information booklet, alert card and record book
As well as lithium levels, what else should be monitored in a patient on lithium for mood stabilisation?
Thyroid function
Renal function
ECG
What monitoring tests are needed for someone starting on lithium as treatment for bipolar affective disorder?
FBC
U+Es
TFTs
Pregnancy test
ECG
