What was most likely the reason for the adverse effects reported by the patient?

Correct Answer: B

Rationale: The correct answer is B: Decreased renal elimination of lithium. Thiazides reduce lithium excretion leading to lithium accumulation and toxicity. Thiazide-induced dilutional hypernatremia (A) is unlikely as thiazides generally cause hyponatremia. Decreased hepatic metabolism of lithium (C) is not a major factor in lithium toxicity. Thiazide-induced hypokalemia (D) is a possible side effect but not the primary reason for lithium toxicity in this scenario.

Correct Answer: B

Rationale: The correct answer is B: Mesolimbic pathway. In ADHD, dysfunction in the mesolimbic pathway, involved in reward and motivation, is often implicated. Stimulant medications like those used to treat ADHD act on this pathway to improve focus and impulse control. The other pathways listed do not play as significant of a role in ADHD symptomatology. A: Tuberoinfundibular is involved in hormonal regulation, not ADHD. C: Corticostriatal is more associated with movement control. D: Mesocortical is related to cognitive functions, but not the main site of therapeutic action for ADHD.

Correct Answer: B

Rationale: The correct answer is B: Dextroamphetamine. This drug is a stimulant commonly prescribed for attention deficit hyperactivity disorder (ADHD) in children. It helps improve focus and control impulsivity, addressing symptoms like inability to sit still in school. Cocaine (A) is a highly addictive illegal drug with no therapeutic use in this context. Methylphenidate (C) is another stimulant used for ADHD. Guanfacine (D) is a non-stimulant medication that is typically used as an alternative treatment for ADHD-related symptoms, but it is less likely to be prescribed for a child unable to sit still in school compared to stimulant medications like Dextroamphetamine.

Correct Answer: D

Rationale: The correct answer is D: Buprenorphine. Buprenorphine is commonly used to treat opioid addiction and dependence due to its partial agonist activity at the mu-opioid receptor, which helps reduce cravings and withdrawal symptoms. Methadone (A) is also used for opioid addiction treatment but is more commonly administered in specialized clinics. Meperidine (B) is primarily used for acute pain management and has a high potential for toxic metabolites. Codeine (C) is a weaker opioid commonly used for mild to moderate pain and cough suppression, not typically used for addiction treatment.

Correct Answer: D

Rationale: The correct answer is D because methadone stimulates adenylyl cyclase activity as a postreceptor mechanism. Methadone is an opioid receptor agonist that activates G-protein coupled receptors, leading to the activation of adenylyl cyclase and subsequent increase in cAMP levels. This increased cAMP signaling pathway results in various downstream effects, including modulation of neurotransmitter release and neuronal excitability. A: Inhibition of the synthesis of inositol triphosphate/diacylglycerol (IP3/DAG) is not a postreceptor mechanism triggered by methadone. B: Blockade of Ca2+ channels on presynaptic nerve terminals is not a postreceptor mechanism triggered by methadone. C: Opening of Na+ channels on neuronal cell membrane is not a postreceptor mechanism triggered by methadone. In summary, methadone's stimulation of adenylyl cyclase activity is the correct choice as it align