Pharmacology Autonomic Nervous System Agents Questions and Answers 1

Question 1

A 68-year-old male with open-angle glaucoma is prescribed pilocarpine eye drops. What is the primary mechanism by which this medication lowers intraocular pressure?

Accepted Answer

Increasing the outflow of aqueous humor by causing contraction of the ciliary muscle.

Answer

Pilocarpine is a direct-acting muscarinic agonist. When administered topically to the eye, it stimulates muscarinic receptors on the ciliary muscle, causing it to contract. This contraction increases tension on the trabecular meshwork, which facilitates the outflow of aqueous humor from the anterior chamber, thereby reducing intraocular pressure.

Question 2

A patient with asthma requires a rescue inhaler for acute bronchospasm. Which of the following agents is most appropriate due to its selective action on bronchial smooth muscle?

Accepted Answer

Albuterol

Answer

Albuterol is a selective beta-2 adrenergic agonist. Beta-2 receptors are predominantly located in the smooth muscle of the bronchioles. Stimulation of these receptors leads to smooth muscle relaxation and bronchodilation, making it an effective treatment for acute asthma symptoms. Phenylephrine is an alpha-1 agonist, norepinephrine acts on alpha-1, alpha-2, and beta-1 receptors, and dobutamine is primarily a beta-1 agonist.

Question 3

A patient is being treated with a medication that has significant anticholinergic properties. Which of the following side effects is most consistent with this drug's profile?

Accepted Answer

Urinary retention

Answer

Anticholinergic agents block the action of acetylcholine at muscarinic receptors. This blockade of the parasympathetic nervous system leads to a classic set of side effects, often remembered by the mnemonic 'can't see, can't pee, can't spit, can't s***'. Urinary retention ('can't pee') is a common side effect due to the relaxation of the bladder detrusor muscle. The other options are characteristic of cholinergic stimulation.

Question 4

A surgeon administers neostigmine to a patient at the end of a procedure to reverse the effects of a non-depolarizing neuromuscular blocker. What is the mechanism of action for neostigmine?

Accepted Answer

It inhibits the breakdown of acetylcholine by acetylcholinesterase.

Answer

Neostigmine is a reversible acetylcholinesterase inhibitor. By inhibiting the enzyme acetylcholinesterase, it prevents the breakdown of acetylcholine in the synaptic cleft. This increases the concentration and duration of action of acetylcholine at the neuromuscular junction, allowing it to outcompete the non-depolarizing blocker and restore neuromuscular transmission.

Question 5

A 72-year-old male treated for benign prostatic hyperplasia (BPH) with tamsulosin, an alpha-1A selective antagonist, reports feeling dizzy, especially when standing up from a seated position. This side effect is best explained by which of the following effects of the drug?

Accepted Answer

Relaxation of vascular smooth muscle.

Answer

Alpha-1 adrenergic antagonists, including tamsulosin, block alpha-1 receptors on vascular smooth muscle. This leads to vasodilation and a decrease in peripheral resistance. A common side effect is orthostatic hypotension, which is a drop in blood pressure upon standing that causes dizziness or lightheadedness.

Pharmacology Practice Test

Pharmacology Practice Test

Pharmacology Autonomic Nervous System Agents Questions and Answers 1