A patient who has been taking isoniazid (INH) has a new prescription for pyridoxine. She is wondering why she needs this medication. The nurse explains that pyridoxine is often given concurrently with the isoniazid to prevent which condition?

Correct Answer: C

Rationale: The correct answer is C: Peripheral neuropathy. Isoniazid (INH) can deplete vitamin B6 levels, leading to peripheral neuropathy. Pyridoxine (vitamin B6) supplementation helps prevent this side effect by replenishing the vitamin. Hair loss (A) is not a common side effect of INH. Renal failure (B) and heart failure (D) are not typically associated with INH therapy. By preventing peripheral neuropathy, pyridoxine helps maintain nerve health and function in patients taking INH.

Correct Answer: C

Rationale: Step-by-step rationale: 1. Idiosyncratic reaction refers to unusual, unpredictable responses to a drug. 2. Choice C correctly defines idiosyncratic reaction as inherent, abnormal, and unpredictable. 3. Choices A and B are incorrect as they do not accurately describe idiosyncratic reactions. 4. Choice A refers to hypersensitivity reactions, not idiosyncratic reactions. 5. Choice B refers to drug antagonism, which is different from idiosyncratic reactions. 6. Choice D is incorrect as it describes a quantitatively exaggerated response, not an idiosyncratic reaction. Summary: Choice C is correct as it accurately defines idiosyncratic reactions. Choices A, B, and D are incorrect as they describe different concepts that do not align with the definition of idiosyncratic reactions.

Correct Answer: C

Rationale: Muscarinic receptors are located in autonomic effector cells. These receptors respond to acetylcholine released by parasympathetic nerves in organs like the heart, smooth muscle, and glands. They play a key role in regulating functions such as heart rate, digestion, and glandular secretions. Autonomic ganglia (A) contain nicotinic receptors, not muscarinic. Skeletal muscle neuromuscular junctions (B) have nicotinic receptors. Sensory carotid sinus baroreceptor zone (D) is not directly involved in cholinergic signaling. Hence, the correct answer is C.

Correct Answer: A

Rationale: Atropine causes spasmolitic activity by blocking acetylcholine receptors, leading to relaxation of smooth muscles. This is beneficial in conditions like irritable bowel syndrome. Intestinal hypermotility, stimulation of gut contraction, and secretory activity are all effects opposite to what atropine causes due to its anticholinergic properties. Atropine's mechanism of action supports choice A as the correct answer.

Correct Answer: C

Rationale: The correct answer is C: Tachycardia. Direct beta1-adrenoreceptor stimulation leads to an increase in heart rate by enhancing the conduction of electrical impulses in the heart. Beta1 receptors are primarily located in the heart, particularly in the sinoatrial node, atria, and ventricles. This stimulation results in an increased rate of depolarization, leading to tachycardia. Choices A and B are incorrect because beta2 receptors are responsible for bronchodilation and vasodilation, respectively. Choice D is incorrect because bradycardia is not associated with direct beta1-adrenoreceptor stimulation.