Question 1
A 28-year-old patient starts escitalopram 10 mg daily for severe depression. After four days of therapy, the patient reports feeling no mood improvement but complains of mild nausea and jitteriness. The FNP explains this expected clinical presentation.
▸ Why B is the answer
The pharmacodynamic delay in the efficacy of selective serotonin reuptake inhibitors is due to the time required for presynaptic somatodendritic 5-HT1A receptor down-regulation. While synaptic serotonin increases immediately upon starting the medication, causing early side effects like nausea and jitteriness via peripheral and off-target receptors, therapeutic mood improvement takes several weeks. Option B correctly identifies this mechanism. Option A is incorrect because synaptic serotonin is increased, not depleted. Option C is incorrect because escitalopram is a highly selective medication without significant norepinephrine activity. Option D is incorrect because these medications do not undergo auto-induction; their delayed onset is a pharmacodynamic receptor adaptation, not a pharmacokinetic enzymatic process.
🔑 Key takeaway
SSRI therapeutic delay results from the time required for serotonin receptor down-regulation.
