WBR0094

Author	[[PageAuthor::Gonzalo Romero (reviewed by Rim Halaby, M.D. [1])]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Behavioral Science/Psychiatry, MainCategory::Pharmacology
Sub Category	SubCategory::Neurology
Prompt	[[Prompt::A 25-year-old male complains of generalized fatigue for over more than 7 months. Upon interrogation, the patient reports he is generally unhappy and lacks motivation at work. He believes his coworkers reject him and admits he does not have any friends. He spends most his time at home sleeping and when he wakes up he is either watching TV or eating fast food. He likes watching comedy shows as they might help improve his mood. The patient also mentions that he feels heaviness in the arms and legs which makes it so hard for him to get out of bed sometimes. He denies suicidal thoughts or feelings of worthlessness. The patient is started on a medication to relieve his symptoms. Which of the following is the mechanism of action of the drug most likely prescribed to this patient?]]
Answer A	AnswerA::Serotonin reuptake inhibitor
Answer A Explanation	[[AnswerAExp::Selective serotonin reuptake inhibitors (SSRIs) include paroxetine, sertraline, citalopram and sertraline and they are used to treat depression, general anxiety disorder, bulimia, social phobia, OCD and post traumatic stress disorder.]]
Answer B	AnswerB::Norepinephrine reuptake inhibitor
Answer B Explanation	[[AnswerBExp::Maprotiline is an atypical antidepressant which blocks norepinephrine reuptake. It can cause sedation as a side effect.]]
Answer C	AnswerC::Serotonin receptor agonist
Answer C Explanation	[[AnswerCExp::Buspirone, which is used to treat general anxiety disorder, stimulates serotonin (5-HT1a) receptors. It does not cause sedation, addiction or tolerance.]]
Answer D	AnswerD::Alpha-2 receptor antagonist
Answer D Explanation	[[AnswerDExp::Mirtazapine is an atypical antidepressant. It blocks alpha-2 receptors in the presynaptic neurons which increases the release of norepinephrine and serotonin. It causes sedation and therefore can be used in depressed patients with insomnia. It might also cause an increase in appetite with possible weight gain.]]
Answer E	AnswerE::GABA positive allosteric modulators
Answer E Explanation	[[AnswerEExp::Different drugs act by increasing the opening of GABA channels such as benzodiazepines and barbiturates.]]
Right Answer	RightAnswer::C
Explanation	[[Explanation::This patient is presenting with atypical depression, the most common subtype of depression. Atypical depression is characterized by hypersomnia and increase in appetite which leads to weight gain. It is also associated with paralysis or a heavy feeling in arms and legs and long-term interpersonal rejection sensitivity. Atypical depression is also characterized by mood reactivity; the patient is able to improve his mood to positive events. The treatment of choice is a MAO inhibitor, which inhibits 5-HT, norepinephrine and dopamine metabolism. MAO inhibitors include phenelzine, tranylcypromine, isocarboxacid and selegiline which is a selective MAO-B inhibitor. MAO inhibitors are used mainly for atypical depression. The major side effects of MAO inhibitor are hypertensive crisis when combined with tyramine, a compound found in cheese and wine. Educational Objective: Atypical depression is characterized by mood reactivity, hypersomnia, weight gain, heaviness in the arms and legs and long-term interpersonal sensitivity to being rejected. The treatment of choice is a MAO inhibitor, which inhibits 5-HT, norepinephrine and dopamine metabolism. References: First Aid 2013 page 472-476]]
Approved	Approved::Yes
Keyword	WBRKeyword::Atypical depression, WBRKeyword::depression, WBRKeyword::psychiatry, WBRKeyword::MOI, WBRKeyword::monoamine oxidase inhibitor
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