WBR0001
| Author | PageAuthor::Anonymous (Reviewed by Will Gibson, Alison Leibowitz, and Yazan Daaboul) |
|---|---|
| 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 SIADH, agranulocytosis, aplastic anemia, hepatotoxicity, Stevens-Johnson syndrome, and teratogenicity.]] |
| Answer B | AnswerB::Gabapentin |
| Answer B Explanation | [[AnswerBExp::Gabapentin is a gamma-aminobutyric acid (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 may be used to treat depression and generalized anxiety disorder. It may also be used in cases of chronic pain. Classically, venlafaxine is associated with an increase in diastolic blood pressure, nausea, and sedation.]] |
| Answer D | AnswerD::Amitriptyline |
| Answer D Explanation | [[AnswerDExp::Amitryptyline is a tertiary amine tricyclic antidepressant (TCA) that blocks the reuptake of serotonin and norepinephrine. It is primarily used to treat major depression. Side effects of amitriptyline include the three C-s: Convulsions, Coma, and Cardiotoxicity. Additionally, TCAs have anticholinergic side effects, such as urinary retention, constipation, dryness of the mouth, and sedation. TCAs do not typically cause hypothyroidism as seen in this patient.]] |
| Answer E | AnswerE::Lithium |
| 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. The mechanism of action of lithium is not poorly understood and is yet to be elucidated. In bipolar disorder, lithium is indicated for the acute treatment of mania as well as for prophylaxis. Less commonly, lithium is used in the management of SIADH. It is almost totally excreted in the urine, potentially causing renal injury. Other well-established side effects of lithium include hypothyroidism, manifested by fatigue, constipation, and menstrual irregularities as observed in this patient. Lithium has other side effects, which can be remembered with the mnemonic LITHIUM:
It is important to perform renal and thyroid function tests before the initiation of therapy. Frequent re-assessment is also required to monitor for potential side effects. |
| Approved | Approved::Yes |
| Keyword | WBRKeyword::Bipolar disorder, WBRKeyword::Lithium, WBRKeyword::Hypothyroidism, WBRKeyword::Side, WBRKeyword::adverse, WBRKeyword::effect, WBRKeyword::Psychiatry, WBRKeyword::Antipsychotic, WBRKeyword::Pharmacology, WBRKeyword::Drug, WBRKeyword::Mania, WBRKeyword::Constipation, WBRKeyword::Fatigue, WBRKeyword::Menstrual |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |