WBR0001

Author	PageAuthor::Anonymous (Edited by Will Gibson)
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Behavioral Science/Psychiatry, MainCategory::Pharmacology
Sub Category	SubCategory::Neurology
Prompt	[[Prompt::A 23-year-old woman presents to her primary care physician's office with symptoms of depressive episodes, insomnia, and decreased appetite. She reports that these symptoms often alternate with episodes of excited mood and euphoria. The patient is referred to a local psychiatrist for treatment of presumed bipolar disorder. After 2 months, the patient returns and reports improvement of her mood swings after she began taking a medication whose name she cannot recall. Unfortunately, she now complains of recent menstrual irregularities, constipation, and fatigue. Which of the following medications was this patient most likely prescribed?]]
Answer A	AnswerA::Carbamazepine
Answer A Explanation	[[AnswerAExp::Carbamazepine is an anticonvulsant and mood-stabilizing drug used primarily in the treatment of epilepsy and bipolar disorder. It is also the first line treatment for trigeminal neuralgia. Carbamazepine stabilizes the inactivated state of voltage-gated sodium channels, thereby reducing the excitability of neurons. Carbamazepine is an inducer of the Cytochrome P-450 system and adverse reactions to Carbamazepine include rash, SIADH, agranulocytosis and teratogenicity.]]
Answer B	AnswerB::Gabapentin
Answer B Explanation	[[AnswerBExp::Gabapentin is a GABA analogue that inhibits voltage-gated calcium channels. It is used to treat epilepsy, peripheral neuropathy and bipolar disorder. Adverse effects include sedation and ataxia.]]
Answer C	AnswerC::Venlafaxine
Answer C Explanation	[[AnswerCExp::Venlafaxine is an SNRI (inhibits serotonin and norepinephrine reuptake) that is used for depression and generalized anxiety disorder.]]
Answer D	AnswerD::Amitriptyline
Answer D Explanation	[[AnswerDExp::Amitryptyline is a tricyclic antidepressant (blocks the reuptake of serotonin and norepinephrine) used primarily for the treatment of major depression. Side effects of TCAs include the three C-s: Convulsions, Coma, and Cardiotoxicity. TCAs do not cause the hypothyroidism seen in this patient.]]
Answer E	AnswerE::Lithium (Lithobid).
Answer E Explanation	[[AnswerEExp::Lithium is a mood-stabilizer used to treat bipolar disorder. Its mechanism of action is poorly understood. One of the side effects of lithium is hypothyroidism, which is responsible for the menstrual irregularities, constipation and fatigue in this patient. Further questioning might reveal other manifestations of hypothyroidism such as cold intolerance.]]
Right Answer	RightAnswer::E
Explanation	[[Explanation::This patient has bipolar disorder and was most likely prescribed Lithium for mood-stabilization, one side effect of which is hypothyroidism. The mechanism of action of lithium is not well established. It can be used to treat bipolar disorder or SIADH. It is important to perform renal function tests and thyroid function tests before and after initiating therapy. Lithium has many side effects, which can be remembered with the mnemonic LITHIUM: Lethargy / Leucocytosis Intentional Tremor Teratogenicity Hypothyroidism Inspidus (Diabetes Inspidus) Urine excess (polyuria) Metallic taste Educational Objective: Lithium is a mood-stabilizer used to treat bipolar disorder; one side effect of Lithium therapy is hypothyroidism. References: First Aid 2012 page 499 Lithium treatment and thyroid abnormalities. Bochetta et al. Clin Pract Epidemiol Ment Health. 2006; 2: 23.]]
Approved	Approved::Yes
Keyword	WBRKeyword::Bipolar disorder, WBRKeyword::Lithium, WBRKeyword::Hypothyroidism, WBRKeyword::Side effect, WBRKeyword::Psychiatry, WBRKeyword::Antipsychotic, WBRKeyword::Pharmacology, WBRKeyword::Drug, WBRKeyword::Mania
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