Phenytoin

Correct Answer: D

Rationale: Phenytoin is a commonly used antiepileptic drug that works by stabilizing neuronal membranes. The correct answer, D) Steady-state mean plasma concentrations vary disproportionately with dose, is accurate because phenytoin exhibits non-linear pharmacokinetics. This means that as the dose increases, the plasma concentration does not increase proportionally, leading to variations in steady-state levels. Option A) Is 20-30% bound to albumin is incorrect because phenytoin is highly protein-bound (usually around 90%), not 20-30%. Option B) Is the drug of choice for absence seizures is incorrect as ethosuximide is typically the preferred choice for treating absence seizures. Option C) Undergoes flow-limited elimination is incorrect because phenytoin undergoes saturable metabolism in the liver, leading to dose-dependent kinetics rather than flow-limited elimination. Understanding the pharmacokinetic properties of phenytoin is crucial for healthcare professionals to ensure appropriate dosing and monitoring. Non-linear kinetics can result in unexpected changes in plasma concentrations with dose adjustments, emphasizing the need for close monitoring and individualized dosing regimens to optimize therapeutic outcomes while minimizing adverse effects.

Correct Answer: A

Rationale: In this NCLEX question about codeine, the correct answer is A) Depresses the cough reflex. Codeine is an opioid medication that acts centrally to suppress the cough reflex in the brainstem. This is a common pharmacological effect of codeine and is why it is often used as a cough suppressant. Option B) Frequently causes diarrhea is incorrect. While opioids can cause constipation as a side effect, diarrhea is not a typical effect of codeine. Option C) Is used to treat nausea caused by morphine is incorrect. Codeine is not typically used to treat nausea caused by morphine. Antiemetic medications are usually prescribed for this purpose. Option D) Occurs in foxglove plants is incorrect. Codeine is not found in foxglove plants; it is derived from the opium poppy plant. Educationally, understanding the pharmacological effects of codeine is crucial for nursing practice, especially when administering this medication to patients. Nurses need to know that codeine suppresses the cough reflex, which can help in managing cough symptoms. Additionally, knowing the side effects and contraindications of codeine is essential to ensure safe medication administration and patient care.

Correct Answer: C

Rationale: In this question, the correct answer is C) \( M_3 \) receptors. When targeting anticholinergic agents for irritative bladder symptoms, focusing on \( M_3 \) receptors is crucial. The \( M_3 \) muscarinic receptor subtype is predominantly located in smooth muscle and plays a significant role in bladder contraction. By blocking \( M_3 \) receptors, the parasympathetic effects on the bladder can be inhibited, leading to reduced urgency and frequency of urination. Option A) \( M_1 \) receptors are mainly located in the CNS and are involved in cognitive functions. Targeting \( M_1 \) receptors would not be effective for treating irritative bladder symptoms. Option B) \( M_2 \) receptors are found in the heart and play a role in regulating heart rate. Targeting \( M_2 \) receptors would not address irritative bladder symptoms. Option D) \( M_4 \) receptors are located in the CNS and are involved in modulating neurotransmitter release. Targeting \( M_4 \) receptors would not directly impact irritative bladder symptoms. Understanding the specific receptor subtypes and their locations is crucial when developing drugs to target specific conditions. This knowledge is essential for researchers, pharmacologists, and healthcare professionals to ensure the effective treatment of various medical conditions, including irritative bladder symptoms.

Correct Answer: C

Rationale: In this question, the correct answer is C) Norepinephrine. Norepinephrine is expected to have the strongest potency at the α-receptor because it is a direct α-adrenergic agonist, specifically targeting α-adrenergic receptors. Norepinephrine has a higher affinity for α-receptors compared to other options. Acetylcholine (option A) is a neurotransmitter that acts on cholinergic receptors, not adrenergic receptors. Epinephrine (option B) has mixed effects on α and β-adrenergic receptors, so it would not have the strongest potency specifically at the α-receptor. Metanephrine (option D) is a metabolite of epinephrine and does not directly bind to adrenergic receptors. Educationally, understanding the potency of different α-adrenergic agonists is crucial in pharmacology and clinical practice. Knowing which agonist has the strongest potency at specific receptors helps healthcare professionals make informed decisions when selecting medications for patients with various conditions such as hypertension or shock.

Correct Answer: A

Rationale: In Parkinson's disease, there is a decrease in dopamine-producing neurons in the substantia nigra region of the brain. This results in an imbalance between dopamine and acetylcholine, leading to motor symptoms characteristic of the disease. Therefore, patients with Parkinson's disease have an abundance of acetylcholine compared to dopamine. Option A, acetylcholine, is the correct answer because of the dopaminergic deficit in Parkinson's disease. Acetylcholine levels are relatively increased due to the lack of dopamine regulation. Options B, C, and D are incorrect: - Dopamine (Option B) is actually decreased in patients with Parkinson's disease, leading to the characteristic motor symptoms. - Epinephrine (Option C) and norepinephrine (Option D) are not directly implicated in the pathophysiology of Parkinson's disease and are not found in abundance in these patients. Understanding the neurotransmitter imbalances in Parkinson's disease is crucial for healthcare providers as it guides the selection of appropriate pharmacological agents for treatment. This knowledge is fundamental for nurses, pharmacists, and other healthcare professionals involved in the care of patients with Parkinson's disease.