How bipolar disorder is tested on Step 1

Duration and severity separate mania from hypomania.

Mania≥ 1 week, or hospitalizationMarked impairment at work or sociallyMay include psychosisDefines bipolar IOften needs hospital careHypomania≥ 4 daysNoticeable change, no marked impairmentNo psychosisBipolar II (with depression)Often goes unreportedvs
Mania vs hypomania. Symptoms include distractibility, impulsivity, grandiosity, flight of ideas, more activity, less need for sleep, and pressured speech.

Lithium

Effective, but dosing depends on kidney handling of sodium.

TremorFine tremor at therapeutic levels; coarse tremorsuggests toxicityThyroidHypothyroidism, goiter; check TSHKidneyNephrogenic DI (ADH resistance); chronic kidneydiseasePregnancyEbstein anomaly (displaced tricuspid valve)ToxicityVomiting, diarrhea, ataxia, confusion, seizures;hemodialysis
Lithium. It is thought to work partly by inhibiting inositol monophosphatase, reducing phosphoinositide signaling.
  • Interactions: thiazides cause volume loss, and the proximal tubule then reabsorbs more sodium and lithium. ACE inhibitors, NSAIDs, and dehydration also raise levels.
  • Monitoring: serum lithium levels, kidney function, TSH, and calcium (lithium can cause hyperparathyroidism).
  • Nephrogenic DI from lithium: amiloride blocks lithium entry into collecting duct cells.

Other mood stabilizers

Choose by phase of illness and side effect profile.

DrugBest useKey adverse effects
ValproateAcute mania, rapid cyclingHepatotoxicity, pancreatitis, weight gain, neural tube defects
CarbamazepineManiaAgranulocytosis, SIADH, Stevens-Johnson syndrome, CYP induction
LamotrigineBipolar depression and maintenanceStevens-Johnson syndrome
Atypical antipsychotics (quetiapine, olanzapine, aripiprazole)Acute mania; some for bipolar depressionMetabolic syndrome, sedation

Antidepressant monotherapy is avoided because it can switch patients into mania.

Related diagnoses

Rule out medical and substance causes.

  • Cyclothymic disorder: at least 2 years of hypomanic and depressive symptoms that do not meet full criteria.
  • Substance- or medication-induced mania: stimulants, corticosteroids, and antidepressants.
  • Medical causes: hyperthyroidism, frontal lobe lesions, and multiple sclerosis can mimic mania.

Worked example

Find the interaction.

functions Worked example — new tremor and confusion

A patient stable on lithium for years is started on hydrochlorothiazide for blood pressure. Two weeks later they have vomiting, a coarse tremor, unsteady gait, and confusion. What happened?

  1. Coarse tremor, ataxia, GI upset, and confusion are signs of lithium toxicity.
  2. Thiazides cause mild volume depletion.
  3. The proximal tubule responds by reabsorbing more sodium and, with it, lithium.
  4. Stop the thiazide and lithium, give fluids, and consider hemodialysis if severe.

Answer. Lithium toxicity caused by thiazide-induced increase in proximal lithium reabsorption.