Phenytoin

Correct Answer: D

Rationale: Phenytoin is a commonly used antiepileptic drug with complex pharmacokinetics. The correct answer, D) Steady-state mean plasma concentrations vary disproportionately with dose, is accurate because phenytoin exhibits nonlinear pharmacokinetics. This means that as the dose increases, the plasma concentration does not increase proportionally, leading to a disproportionate rise in concentration at higher doses, hence the variability in steady-state concentrations. Option A) Is 20-30% bound to albumin is incorrect because phenytoin is highly protein-bound (usually around 90%), primarily to albumin. Option B) Is the drug of choice for absence seizures is incorrect as ethosuximide is typically the first-line 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 changes in clearance rather than flow-limited elimination. Understanding the pharmacokinetic properties of phenytoin is crucial for healthcare providers managing patients with epilepsy to achieve optimal therapeutic outcomes while minimizing the risk of toxicity. By grasping these concepts, nurses and other healthcare professionals can safely administer and monitor phenytoin therapy, ensuring effective seizure control and patient safety.

Correct Answer: A

Rationale: The correct answer is A) Depresses the cough reflex. Codeine is a central nervous system depressant that acts on the brain to suppress the cough reflex. This makes it effective in treating cough symptoms. Option B) Frequently causes diarrhea is incorrect because codeine is actually known to cause constipation as a side effect due to its action on the gastrointestinal system. Option C) Is used to treat nausea caused by morphine is incorrect as codeine is not typically used to treat nausea caused by morphine. It is more commonly used for pain relief and cough suppression. Option D) Occurs in foxglove plants is incorrect because codeine is not found in foxglove plants. Codeine is actually derived from the opium poppy plant. In an educational context, it is important for nursing students to understand the pharmacological effects of codeine and how it is used in clinical practice. Understanding the correct use of codeine, its side effects, and its contraindications is crucial for safe and effective nursing care. This question helps reinforce the knowledge required for nursing students to make informed decisions regarding the use of central nervous system stimulants and related drugs in their practice.

Correct Answer: C

Rationale: In this scenario, the correct answer is Option C) \( M_3 \). The rationale behind this is that \( M_3 \) receptors are predominantly located in smooth muscle, including the detrusor muscle of the bladder. Activation of \( M_3 \) receptors leads to smooth muscle contraction, which can exacerbate irritative bladder symptoms. By targeting \( M_3 \) receptors with an anticholinergic agent, a researcher can inhibit this smooth muscle contraction, thereby helping to alleviate irritative bladder symptoms. On the other hand, Options A) \( M_1 \), B) \( M_2 \), and D) \( M_4 \) are incorrect choices for this specific scenario. \( M_1 \) receptors are mainly found in the CNS and play a role in memory and learning. \( M_2 \) receptors are also primarily located in the CNS, modulating neurotransmitter release. \( M_4 \) receptors are found in the striatum and regulate dopamine release. From an educational perspective, understanding the specific receptor subtypes and their locations is crucial in pharmacology. This knowledge helps healthcare professionals design targeted interventions for different conditions by selecting drugs that act on specific receptors. In the context of treating irritative bladder symptoms, targeting \( M_3 \) receptors with an anticholinergic agent can provide symptomatic relief by inhibiting detrusor muscle contractions.

Correct Answer: C

Rationale: The correct answer is C) Norepinephrine. Norepinephrine is expected to have the strongest potency at the α-receptor because it is a direct agonist that specifically acts on α-adrenergic receptors. Norepinephrine has a higher affinity for α-receptors compared to other options. Option A, Acetylcholine, is a neurotransmitter that acts on cholinergic receptors, not α-adrenergic receptors. Option B, Epinephrine, while also an adrenergic agonist, has a higher affinity for β-adrenergic receptors rather than α-receptors. Option D, Metanephrine, is a metabolite of epinephrine and does not directly act on adrenergic receptors. In an educational context, understanding the selectivity and potency of different adrenergic agonists is crucial in pharmacology. Knowing which agonist acts on which receptor subtype can help in predicting their physiological effects and clinical applications. This knowledge is essential for healthcare professionals when prescribing medications that target the adrenergic system to achieve specific therapeutic outcomes.

Correct Answer: A

Rationale: The correct answer is A) Acetylcholine. In Parkinson's disease, there is a loss of dopaminergic neurons in the substantia nigra of the brain, leading to a decrease in dopamine levels. This dopamine deficiency results in an imbalance between dopamine and acetylcholine, causing an excess of acetylcholine activity in the basal ganglia. This imbalance contributes to the motor symptoms seen in Parkinson's disease, such as tremors, rigidity, and bradykinesia. Option B) Dopamine is incorrect because, as mentioned earlier, Parkinson's disease is characterized by a lack of dopamine due to the degeneration of dopaminergic neurons. Option C) Epinephrine and Option D) Norepinephrine are also incorrect as they are not primarily involved in the pathophysiology of Parkinson's disease. While norepinephrine plays a role in the sympathetic nervous system, it is not the neurotransmitter primarily affected in Parkinson's disease. Understanding the neurotransmitter imbalance in Parkinson's disease is crucial for healthcare professionals to provide appropriate treatments such as dopamine replacement therapies or medications that target the acetylcholine-dopamine imbalance. This knowledge is also essential for nurses and other healthcare providers in educating patients and families about the disease process and rationale behind treatment strategies.