Phenytoin has a narrow therapeutic index.
The nurse recognizes that this characteristic indicates which of these?
The safe and the toxic plasma levels of the drug are very close to each other.
The phenytoin has a low chance of being effective.
There is no difference between safe and toxic plasma levels.
A very small dosage can result in the desired therapeutic effect.
A very small dosage can result in the desired therapeutic effect.
The Correct Answer is A
Choice A rationale:
Phenytoin is an anticonvulsant drug used in the prophylaxis and control of various types of seizures. It has a narrow therapeutic index, which means that the safe and toxic plasma levels of the drug are very close to each other. This characteristic makes the dosing of phenytoin challenging, as even small deviations from the recommended therapeutic range can lead to suboptimal treatment or adverse effects. Therapeutic effect without clinical signs of toxicity occurs more often with serum total concentrations between 10 and 20 mcg/mL34. Therefore, clinicians are advised to initiate therapeutic drug monitoring in patients who require phenytoin.
Choice B rationale:
The statement that phenytoin has a low chance of being effective is incorrect. Phenytoin is a widely used and effective anticonvulsant. It works by slowing down impulses in the brain that cause seizures. It is used to control seizures but does not treat all types of seizures. The effectiveness of phenytoin is not determined by its narrow therapeutic index but by its pharmacological action in the brain.
Choice C rationale:
The assertion that there is no difference between safe and toxic plasma levels of phenytoin is incorrect. There is indeed a difference between the safe (therapeutic) and toxic levels of phenytoin. The therapeutic range for phenytoin is typically between 10 and 20 mcg/mL34. Levels above this range can lead to toxicity, while levels below this range may not provide the desired therapeutic effect.
Choice D rationale:
The statement that a very small dosage of phenytoin can result in the desired therapeutic effect is not entirely accurate. While it’s true that phenytoin is effective in controlling seizures, the dosage required to achieve this effect is not necessarily “very small”. The usual adult dose for seizures is 100 mg orally 3 times a day. The dosage may need to be adjusted based on individual patient factors and response to therapy. Therefore, it’s not accurate to generalize that a “very small” dosage will result in the desired therapeutic effect for all patients.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is ["B","C","D"]
Explanation
Choice A rationale:
Polyuria, which is frequent or excessive urination, is not typically a symptom of hypoglycemia. It is more commonly associated with hyperglycemia, or high blood sugar levels.
Choice B rationale:
Sweating is indeed a common symptom of hypoglycemia. When blood sugar levels fall too low, the body may respond by sweating as it releases adrenaline in response to the hypoglycemic state.
Choice C rationale:
Tachycardia, or a fast heartbeat, is another common symptom of hypoglycemia. This is part of the body’s response to low blood sugar levels, as it releases adrenaline to try to raise these levels.
Choice D rationale:
Blurry vision can be a symptom of hypoglycemia. When blood sugar levels fall, it can affect the ability of the eyes to focus, leading to blurry vision.
Choice E rationale:
Polydipsia, or excessive thirst, is not typically a symptom of hypoglycemia. Like polyuria, it is more commonly associated with hyperglycemia.
Correct Answer is C
Explanation
Choice A rationale:
Waiting to see if the fever gets worse is not the best course of action. Fever is a symptom that the body is fighting off an infection, and it can cause discomfort in children. However, the main concern with chickenpox and fever is not the fever itself, but the risk of complications from the chickenpox. Therefore, it’s important to manage the fever for the child’s comfort but also monitor for any signs of complications.
Choice B rationale:
Aspirin should not be given to children or teenagers who have chickenpox or flu symptoms before a doctor is consulted about Reye’s Syndrome, a rare but serious illness. Reye’s syndrome is a potentially life-threatening condition that has been associated with aspirin use in children and adolescents with viral illnesses, especially chickenpox or influenza.
Choice C rationale:
Acetaminophen (Tylenol) should be used to reduce his fever, not aspirin. This is because of the risk of Reye’s syndrome associated with aspirin use in children and adolescents who have viral illnesses. Acetaminophen is a safe and effective choice for fever reduction in children.
Choice D rationale:
While it’s important to always follow the instructions on the bottle when giving medication, aspirin should not be used in children or teenagers with chickenpox due to the risk of Reye’s syndrome. Therefore, this advice could potentially lead to a dangerous situation.
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