Neurological Disorders Q 100

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A female client complains of periorbital aching, tearing, blurred vision, and photophobia in her right eye. Ophthalmologic examination reveals a small, irregular, nonreactive pupil — a condition resulting from acute iris inflammation (iritis). As part of the client’s therapeutic regimen, the physician prescribes atropine sulfate (Atropisol), two drops of 0.5% solution in the right eye twice daily. Atropine sulfate belongs to which drug classification?

  

     A. Parasympathomimetic agent

     B. Sympatholytic agent

     C. Adrenergic blocker

     D. Cholinergic blocker

    

    

Correct Answer: D. Cholinergic blocker

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Atropine sulfate is a cholinergic blocker. It isn’t a parasympathomimetic agent, a sympatholytic agent, or an adrenergic blocker. Atropine is an antimuscarinic that works through competitive inhibition of postganglionic acetylcholine receptors and direct vagolytic action, which leads to parasympathetic inhibition of the acetylcholine receptors in smooth muscle.

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Option A: Parasympathomimetics are a class of pharmacological agents that activate the parasympathetic division of the autonomic nervous system. These drugs work by mimicking or modifying the effects of acetylcholine (ACh), the primary neurotransmitter of the parasympathetic nervous system. Parasympathomimetic medications are classified into two main categories based on whether they are direct agonists or indirect agonists of ACh.

Option B: Methyldopa is a centrally acting sympatholytic agent used in the treatment of hypertension. Alpha-methyldopa is converted to methyl norepinephrine centrally to decrease the adrenergic outflow by alpha-2 agonist action from the central nervous system, leading to reduced total peripheral resistance and decreased systemic blood pressure.

Option C: The effects of the sympathetic nervous system can be blocked either by decreasing sympathetic outflow from the brain, suppressing release of norepinephrine from terminals, or by blocking postsynaptic receptors. Adrenergic antagonists reduce the effectiveness of sympathetic nerve stimulation and the effects of exogenously applied agonists, such as isoproterenol. Most often the receptor antagonists are divided into ?-receptor antagonists and ?-receptor antagonists.

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