A patient has been given a prescription for levodopa-carbidopa (Sinemet) for her newly diagnosed Parkinson’s disease. She asks the nurse, “Why are there two drugs in this pill?” The nurse’s best response reflects which fact?
Carbidopa allows for larger doses of levodopa to be given.
Carbidopa prevents the breakdown of levodopa in the periphery.
There are concerns about drug-food interactions with levodopa therapy that do not exist with the combination therapy.
Carbidopa is the biologic precursor of dopamine and can penetrate into the central nervous system.
The Correct Answer is B
Choice A reason: Carbidopa does not allow larger levodopa doses but reduces the dose needed by preventing peripheral breakdown. This increases levodopa’s availability to cross the blood-brain barrier, improving efficacy without increasing side effects like nausea from peripheral dopamine.
Choice B reason: Carbidopa inhibits peripheral dopa decarboxylase, preventing levodopa’s conversion to dopamine outside the brain. This increases levodopa’s central nervous system availability, enhancing dopamine production in the basal ganglia to alleviate Parkinson’s symptoms, making it the primary reason for the combination.
Choice C reason: Drug-food interactions (e.g., protein competing with levodopa absorption) persist with levodopa-carbidopa, as carbidopa does not affect intestinal absorption. This is not the primary reason for the combination, which focuses on peripheral metabolism inhibition.
Choice D reason: Carbidopa is not a dopamine precursor and cannot cross the blood-brain barrier. Levodopa is the precursor, converted to dopamine in the brain. Carbidopa’s role is to block peripheral conversion, not to act as a precursor itself.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is C
Explanation
Choice A reason: Dairy products like milk and yogurt are rich in calcium, essential for bone mineralization. Calcium supports osteoblast activity, strengthening bones and preventing osteoporosis progression, making this a correct dietary choice for bone health.
Choice B reason: Green leafy vegetables like spinach provide calcium and vitamin K, which supports bone matrix formation and mineralization. Including these in the diet is beneficial for osteoporosis, as they enhance bone density, indicating correct understanding.
Choice C reason: Excessive coffee intake increases urinary calcium excretion, reducing available calcium for bone formation. Caffeine also inhibits osteoblast activity, worsening bone loss in osteoporosis, indicating a misunderstanding of dietary impacts on bone health, requiring further teaching.
Choice D reason: Taking a calcium supplement with a meal enhances absorption, as stomach acid aids calcium ionization. This supports bone mineralization in osteoporosis, reflecting correct understanding of dietary supplementation to improve bone density and prevent fractures.
Correct Answer is C
Explanation
Choice A reason: Stress fractures result from repetitive microtrauma, common in athletes, not typically associated with abuse. In children, they occur from overuse (e.g., sports), not acute trauma, making them less suspicious for non-accidental injury compared to other fracture types.
Choice B reason: Compound fractures, where bone pierces the skin, result from high-impact trauma (e.g., falls). While possible in abuse, they are less specific, as they occur in accidents, making them less indicative of non-accidental injury than spiral fractures.
Choice C reason: Spiral fractures occur from twisting forces, often seen in abuse when a limb is forcefully twisted (e.g., by an adult). In children, whose bones are flexible, spiral fractures suggest significant force, raising suspicion of non-accidental trauma.
Choice D reason: Greenstick fractures, where the bone bends and partially breaks, are common in children due to pliable bones. They occur in accidents or minor trauma, making them less specific to abuse compared to spiral fractures’ association with twisting mechanisms.
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