Answers

1. B. The resting level of vagal stimulation of the heart decreases with age, which is typically accompanied by a gradual increase in heart rate with age. Therefore, the tachycardia produced by atropine is greater in young patients with strong vagal tone, and the response decreases with age in parallel with the decrease in vagal tone.

2 C. Atropine will not directly paralyze the respiratory muscles. However, it can prevent the detection of early signs of an overdose of neostigmine, which can quickly progress to a depolarizing block of skeletal muscle and paralysis of the respiratory muscles. Dry mouth, ocular disturbances, and tachycardia are common side effects of atropine given alone, but these effects are less likely to occur with competition between atropine and the increase in the synaptic ACh produced by inhibition of AChE by neostigmine.

3 A. Application of tropicamide to the eye of a patient with narrow-angle (angle-closure) glaucoma is a very serious risk, because the peripheral movement of the relaxed iris can block the outflow of fluid and trigger a rapid rise in intraocular pressure. Open-angle glaucoma does not present the same risk for the application of a short-acting mydriatic such as tropicamide. If the patient is taking a cholinomimetic miotic for open-angle glaucoma, there is even less risk of applying tropicamide, although potential competition between the miotic and the antagonist may have to be considered.

4 A. Atropine has little effect on blood pressure in the absence of a circulating muscarinic agonist because the muscarinic receptors on endothelial cells do not receive synaptic input. Therefore, the blood pressure of a healthy patient will not change with treatment with atropine. In contrast, patients being treated with an AChE inhibitor may have slightly elevated plasma ACh levels, and patients being treated with bethanechol may be hypotensive because of its direct actions on the muscarinic receptors on endothelial cells.

5 B. The symptoms are suggestive of central antimus-carinic effects of a drug. Glaucoma is treated with muscarinic agonists or noncholinergic drugs. Although the entry of pilocarpine into the CNS can disturb CNS function, it is not as likely as an an-timuscarinic drug to produce drowsiness and loss of concentration. The other questions would all be useful. A patient who has hay fever or stuffiness may be taking an antihistamine. A patient with back spasms may be taking a muscle relaxant, such as cy-clobenzaprine. One who is being treated for mood disorders may be taking antipsychotic medication.

All of these treatments can produce significant central antimuscarinic side effects.

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