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Chapter 9: Sympathomimetics

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A 7-year-old boy with a previous history of bee sting allergy is brought to the emergency department after being stung by 3 bees.

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Which of the following are probable signs of the anaphylactic reaction to bee stings?

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(A) Bronchodilation, tachycardia, hypertension, vomiting, diarrhea

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(B) Bronchospasm, tachycardia, hypotension, laryngeal edema

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(C) Diarrhea, bradycardia, vomiting

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(D) Laryngeal edema, bradycardia, hypotension, diarrhea

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(E) Miosis, tachycardia, vomiting, diarrhea

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Anaphylaxis is caused by the release of several mediators. Leukotrienes and certain proteins are the most important of these. They cause bronchospasm and laryngeal edema and marked vasodilation with severe hypotension. Tachycardia is a common reflex response to the hypotension. Gastrointestinal disturbance is not as common nor as dangerous. The answer is B.

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A 7-year-old boy with a previous history of bee sting allergy is brought to the emergency department after being stung by 3 bees.

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If this child has signs of anaphylaxis, what is the treatment of choice?

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(A) Diphenhydramine (an antihistamine)

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(B) Ephedrine

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(C) Epinephrine

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(D) Isoproterenol

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(E) Methylprednisolone (a corticosteroid)

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The treatment of anaphylaxis requires a powerful physiologic antagonist with the ability to cause rapid bronchodilation (β2 effect), and vasoconstriction (α effect). Epinephrine is the most effective agent with these properties. Antihistamines and corticosteroids are sometimes used as supplementary agents, but the prompt parenteral use of epinephrine is mandatory. The answer is C.

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A 65-year-old woman with impaired renal function and a necrotic ulcer in the sole of her right foot is admitted to the ward from the emergency department. She has long-standing type 2 diabetes mellitus and you wish to examine her retinas for possible vascular changes. Which of the following drugs is a good choice when pupillary dilation—but not cycloplegia—is desired?

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(A) Isoproterenol

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(B) Norepinephrine

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(C) Phenylephrine

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(D) Pilocarpine

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(E) Tropicamide

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Antimuscarinics (tropicamide) are mydriatic and cycloplegic; α-sympathomimetic agonists are only mydriatic in the eye. Isoproterenol has negligible effects on the eye. Norepinephrine penetrates the conjunctiva poorly and would produce intense vasoconstriction. Pilocarpine causes miosis. Phenylephrine is well-absorbed from the conjunctival sac and produces useful mydriasis for 10–30 minutes. The answer is C.

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