Which of the following antimuscarinic drugs is a selective M1 blocker?

Correct Answer: C

Rationale: The correct answer is C: Pirenzepine. Pirenzepine is a selective M1 blocker because it specifically targets the M1 subtype of muscarinic receptors. This selectivity reduces the likelihood of off-target effects associated with non-selective antimuscarinic drugs. Atropine (choice A) and Scopolamine (choice B) are non-selective antimuscarinic drugs, affecting multiple muscarinic receptor subtypes. Homatropine (choice D) is a non-selective antimuscarinic drug primarily used for its mydriatic effect in ophthalmology. Therefore, the correct choice is C as it is the only drug that selectively blocks the M1 receptor subtype.

Correct Answer: A

Rationale: The correct answer is A: Drug-induced parkinsonism. Sympathomimetics stimulate the sympathetic nervous system, which can lead to adverse effects like cerebral hemorrhage, pulmonary edema, myocardial infarction, and ventricular arrhythmias due to increased heart rate and blood pressure. However, they do not cause drug-induced parkinsonism, which is associated with medications that affect dopamine levels in the brain. Therefore, choice A is the correct answer. Choices B, C, and D are incorrect because sympathomimetics can indeed lead to these adverse effects due to their actions on the sympathetic nervous system.

Correct Answer: C

Rationale: The correct answer is C because hypnotic drugs are primarily used to induce drowsiness and promote sleep. They help with insomnia and encourage the onset and maintenance of sleep. This is achieved by affecting the brain's neurotransmitters and promoting relaxation. Options A and D are incorrect as hypnotic drugs are not intended to specifically reduce anxiety, exert a calming effect, or prevent mood swings in patients with bipolar affective disorders. Option B is incorrect as hypnotic drugs do not induce an absence of sensation; that would be more characteristic of anesthetics.

Correct Answer: A

Rationale: Sure! Valproate is the correct answer as it is used as an anti-absence drug due to its effectiveness in treating absence seizures. Valproate works by enhancing the activity of a neurotransmitter called gamma-aminobutyric acid (GABA), which helps to calm overactive brain activity that causes absence seizures. Phenobarbital, Carbamazepine, and Phenytoin are not typically used to treat absence seizures, as they are more commonly used to treat other types of seizures such as tonic-clonic seizures or focal seizures.

Correct Answer: B

Rationale: Levodopa is the precursor of dopamine as it is converted into dopamine in the brain. Bromocriptine is a dopamine agonist, not a precursor. Selegiline is a MAO-B inhibitor that helps preserve dopamine, not a precursor. Amantadine is an antiviral drug with unclear mechanisms regarding dopamine production. Therefore, B is the correct answer.