Preparation for Child Psych PRITE and Boards
Revision as of 15:22, 15 October 2010 by Eugene Grudnikoff MD (Talk | contribs) (→High-Yield Facts)
Contents
Introduction
Lithium, the lightest solid element on the periodic table, has a central role in managing pediatric bipolar disorder. This article describes the properties of lithium as a medication. For its role in the overall treatment guidelines, see the article on bipolar disorder.
Adult Psychiatry Review
- Lithium is effective in acute mania management and bipolar prophylaxis.
- Lithium has psychoactive properties only as a positively-charged ion, Li+; to this end, it is manufactured as a salt, i.e. lithium carbonate or lithium chloride. Lithium carbonate causes less GI irritation and, thus, preferred to LiCl. Lithium citrate is available in a syrup form.
- There is no "lithium receptor." It acts on many receptors, channels, and intracellular proteins. Among other effects it inhibits intracellular adenylyl cyclase, an enzyme in the second-messenger cascade of TSH, vasopressin (ADH), and many other cell processes. A serious side effect of lithium are hypothyroidism and failure to concentrate urine.
- Lithium has low therapeutic index (ratio of toxic level to therapeutic level, 1.5mM/1.0mM = 1.5) or a narrow therapeutic range (0.8 to 1.2mM). Levels are drawn 12hrs after last dose, 4-5 days after dose change (half-life ~ 24hrs).
- Li+ is excreted by the kidney; as a tiny cation, it is freely filtered at the glomerulus and reabsorbed at the proximal tubule. Therefore, its excretion is directly related to GFR; reduce lithium dose in the elderly
- Since reabsorption of Li+ and Na+ is competitive at the proximal tubule, hyponatremia (low Na+ diet, thiazides, dehydration) can lead to increase in Li+ rebasorption and toxicity, as it is returned to circulation. NSAIDs, carbamazepine, and tetracyclines can also precipitate lithium toxicity.
- Loop diuretics (furosemide), caffeine facilitate lithium excretion.
How to Start and Monitor
- Baseline assessment: H&P (including height and weight), calculate BMI,
- Labs: UA, Upreg, TSH, free T4, CBC, CMP (electrolytes, BUN, creatinine, calcium, albumin). Repeat q3-6mo and with dose adjsutment;
- Starting dose is 300mg BID (or qPM - maybe easier on the kidney, but causes higher peak level) and titrate weekly to 1500mg +/-300mg, to plasma levels of 1.0mM. Check levels 5 days after starting treatment.
- Check lithium levels q3-6mo and after each dose adjustment; lithium levels should be drawn 12 hr after last dose (e.g. in the AM before morning dose); therapeutic plasma level is between 0.8 and 1.2mEq/L.
Adverse Effects
Common | Thirst, polyuria, fatigue, nausea, diarrhea, tremor, ataxia, acne, cognitive dulling, weight gain |
Other | benign leukocytosis, mild hypercalcemia, exacerbation of psoriasis, intermittent edema, EKG changes |
Rare | nephorgenic diabetes insipidus, EPS worsening |
Teratogenicity | small increase in risk in tricuspid valve disease and Ebstein's anomaly in the 1st trimester. Despite low risk, ECT and antipsychotics are preferred in pregnancy |
Toxicity | may develop at therapuetic levels with symptoms of nausea, agitation, vomiting, diarrhea, muscle weakness, coarse tremor, renal failure; thinking of a drunk person can be helpful when memorizing the signs and symptoms of toxicity |
Managing Lithium Overdose
- Acutely, ensure ABCs, including intubation if necessary.
- Induction of vomiting/gastric lavage if overdose occurred < 4hrs ago,
- Continual gastric aspiration (NG tube) since lithium can be removed from gastric secretions
- Normal saline hydration if urine output is adequate. Hemodialysis is indicated in renal insufficiency and failure.
Clinical Considerations in Children and Adolescents
- Lithium is not approved (but frequently used) for children <12yo.
- Lithium had been studied and found effective for short-term maintenance treatment of bipolar disorder, for decreasing aggression, and for treatment of acute depression in teens (Lewis's 769). Thus, lithium may be a good option in depressed teens who need to regain functionality sooner than would be expected from an SSRI therapy.
- Lithium is generally well tolerated in pediatric population, and more effective than other mood stabilizers in preventing relapse.
- Children may need higher doses than adults, as they have higher GFR, leading to shorter lithium half-life in circulation, higher total body water to weight ratio (lithium is distributed through TBW), and lower ratio of brain-to-serum lithium concentrations.
- Dosing can start at 300mg BID and titrated up to 1000mg daily dose for children (10-30 mg/kg) and 1600mg/day for teens. Just like with adults, maintenance treatment usually requires lower dosages.
- Elevated TSH without decrease in T4 or symptoms of hypothyroidism can be tolerated with frequent monitoring and education.
- WBC count up to 15,000 cells/mm3 in asymptomatic children can be tolerated as well.
- Encourage contraception in female adolescents.
- Consider long-acting preparation to improve compliance and decrease polyuria.
High-Yield Facts
- Lithium orotate is a lithium salt marketed as a supplement and available without prescription. While its efficacy had not been adequately studied, it can cause toxicity just like lithium carbonate.
- While monitoring, check T4 in addition to TSH, since elevated TSH may be inconsequential.
- Acne and weight gain can be particularly distressing to teens on lithium.
- Benign tremor can be managed with prn propranolol.
- Disruption of sodium balance (dehydration, NSAIDs, etc) is the most common cause of toxicity, not overdose.
- Dialysis is indicated if levels are greater than 3mM with sx/s of toxicity, or greater than 4mM.
- Lithium and clozapine are two drugs that have shown do decrease suicidality.
References
Lewis's Child and Adolescent Psychiatry 2007 Handbook of Psychiatric Drug Therapy 2010
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