A nurse is caring for a client who is experiencing anaphylactic shock in response to the administration of penicillin. Which of the following medications should the nurse administer first?

The correct answer is D: Epinephrine. Epinephrine is the first-line medication for anaphylactic shock due to its vasoconstrictive and bronchodilator effects, which help reverse the severe vasodilation and bronchoconstriction seen in anaphylaxis. Administering epinephrine promptly can improve blood pressure, heart rate, and airway patency, preventing cardiovascular collapse. Methylprednisolone (A) is a corticosteroid that may be given later to reduce inflammation. Dobutamine (B) is a beta-adrenergic agonist used for heart failure, not for anaphylactic shock. Furosemide (C) is a diuretic used for fluid overload, not for anaphylactic shock.