Narcolepsy is treated with:

Correct Answer: A

Rationale: The correct answer is A: Amphetamine. Amphetamine is a central nervous system stimulant that helps manage narcolepsy symptoms by promoting wakefulness. It increases levels of neurotransmitters like dopamine and norepinephrine, enhancing alertness. Adrenaline (B), Isoprenaline (C), and Salbutamol (D) are not typically used to treat narcolepsy as they do not directly target the underlying cause of excessive daytime sleepiness. Adrenaline and Isoprenaline are more commonly used for acute situations like anaphylaxis or cardiac arrest. Salbutamol is a bronchodilator used for conditions like asthma.

Correct Answer: D

Rationale: The correct answer is D: Guanethidine. Guanethidine is a quaternary amine, which prevents it from passing the blood-brain barrier due to its charge. The blood-brain barrier is selective and only allows certain molecules to pass through. In contrast, choices A, B, and C (Ephedrine, Propranolol, Clonidine) are all capable of crossing the blood-brain barrier to some extent due to their chemical properties. Ephedrine is a weak base, Propranolol is lipophilic, and Clonidine is relatively small in size, allowing them to penetrate the blood-brain barrier.

Correct Answer: D

Rationale: The correct answer is D: Blood pressure. Ganglion blockers, similar to atropine, block the transmission of nerve impulses at ganglia. Ganglion blockers affect the eye, gastrointestinal tract, and urinary bladder by inhibiting parasympathetic activity. However, ganglion blockers do not have a significant direct effect on blood pressure regulation. Blood pressure is primarily regulated by the autonomic nervous system through the actions of the sympathetic and parasympathetic systems, not solely at ganglia. Therefore, the correct answer is D because ganglion blockers do not directly influence blood pressure regulation.

Correct Answer: D

Rationale: The correct answer is D: Ergot alkaloids. Ergot alkaloids, such as ergotamine and dihydroergotamine, are known to be effective in treating migraines by constricting blood vessels in the brain. This helps to reduce the intensity of migraine headaches. Vinca alkaloids (A) are used in cancer treatment, digitalis glycosides (B) in heart conditions, and stramonium alkaloids (C) in asthma and spasms, but they are not commonly associated with migraine treatment.

Correct Answer: D

Rationale: The correct answer is D: Propranolol. Propranolol is a non-selective beta-blocker that can trigger severe bronchospasm in patients with asthma by blocking beta-2 receptors in the lungs, leading to bronchoconstriction. Atropine (A) is an anticholinergic drug that dilates the airways. Isoproterenol (B) is a beta-agonist that relaxes the airway smooth muscles. Phenylephrine (C) is a sympathomimetic drug that constricts blood vessels, not airways.