The healthcare provider orders Compazine 10 mg IM now. The concentration available is Compazine 5 mg/mL. How many mL will the patient receive?

Choice A reason: Antidotes counteract specific toxins or drugs (e.g., naloxone for opioids). Antihistamines don’t neutralize allergens but block histamine receptors to reduce allergic symptoms like itching or sneezing. They target H1 or H2 receptors, not a toxin, making this choice incorrect for describing antihistamine mechanism of action.

Choice B reason: Antihistamines are antagonists, binding to histamine receptors (H1 or H2) without activating them, preventing histamine from triggering allergic responses like vasodilation or bronchoconstriction. This competitive inhibition reduces symptoms such as itching, sneezing, or gastric acid secretion, making this the correct choice for their pharmacological action.

Choice C reason: Agonists activate receptors to produce a response. Antihistamines block histamine receptors, not activate them, preventing allergic effects. Acting as agonists would mimic histamine, worsening symptoms like swelling or itching, which is opposite to their therapeutic role, making this choice incorrect.

Choice D reason: Activators is a vague term not used in pharmacology to describe drug action. Antihistamines specifically act as receptor antagonists, not general activators. They inhibit histamine effects without stimulating other pathways, making this choice inaccurate for explaining the mechanism of antihistamines in allergy management.

Choice A reason: Drugs with toxic side effects, like chemotherapy agents, can affect multiple organs (e.g., liver, kidneys, heart). Monitoring organ function through lab tests (e.g., LFTs, creatinine) detects early toxicity, allowing timely intervention. Patient education on this ensures adherence and awareness, making this the most comprehensive and proactive approach.

Choice B reason: Ordering complete blood counts is relevant for drugs affecting bone marrow (e.g., chemotherapy), but it’s too narrow. Toxic drugs may impact other organs like the liver or kidneys, requiring broader monitoring (e.g., LFTs, renal panels). Focusing solely on blood counts misses other potential toxicities, making this choice incomplete.

Choice C reason: Discontinuing all medications is drastic and inappropriate without assessing the drug’s benefits versus risks. Many toxic drugs (e.g., methotrexate) are essential for treatment. Monitoring and managing side effects are preferred to maintain therapy efficacy while minimizing harm, making this choice clinically unsound.

Choice D reason: Waiting for symptoms before follow-up risks missing subclinical toxicity, as many drug-induced organ damages (e.g., hepatotoxicity) are asymptomatic initially. Proactive monitoring of organ function through lab tests is essential to detect issues early, making this reactive approach inadequate for managing drugs with known toxic effects.