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 D
Explanation
Choice A rationale:
Insulin is not absorbed most rapidly when injected in the thigh. The abdomen is actually the preferred site for insulin injection as insulin is absorbed more quickly and predictably there. The thigh is a simple area for self-injection, but regular injections in the thigh can sometimes cause discomfort when walking or running afterward.
Choice B rationale:
Using cold insulin for injection to minimize site pain is not recommended. Insulin should be at room temperature. Cold insulin might make the injection more painful.
Choice C rationale:
Massaging the site after injection to promote absorption is not advised. It can cause the insulin to be absorbed too quickly which can lead to low blood glucose levels.
Choice D rationale:
Rotating the injection site to keep insulin levels consistent is the correct choice. People who take insulin daily should rotate their injection sites. This is important because using the same spot over time can cause lipodystrophy. In this condition, fat either breaks down or builds up under the skin, causing lumps or indentations that interfere with insulin absorption.
Correct Answer is D
Explanation
Choice A rationale:
Administering the antibiotic dose before obtaining the cultures could potentially affect the results of the cultures. Antibiotics are designed to kill or inhibit the growth of bacteria, so administering them before obtaining the cultures could lead to false negatives. This could lead to incorrect or delayed diagnosis and treatment.
Choice B rationale:
While obtaining the urine culture before administering the antibiotic dose is a good step, it should not be done before obtaining the blood culture. Blood cultures are usually obtained before urine cultures because they can help identify bacteria or fungi in the blood. This can be crucial in diagnosing conditions like sepsis. Furthermore, administering the antibiotic dose before obtaining the blood culture could affect the results of the culture.
Choice C rationale:
Obtaining the blood culture before administering the antibiotic dose is a good step, but the urine culture should also be obtained before the antibiotic dose is administered. Administering the antibiotic dose before obtaining all necessary cultures could affect the results of the cultures and lead to incorrect or delayed diagnosis and treatment.
Choice D rationale:
This is the correct sequence of actions. The nurse should first obtain both blood and urine cultures before administering the antibiotic dose. This is because the antibiotic could potentially kill or inhibit the growth of bacteria, which could affect the results of the cultures. By obtaining the cultures first, the healthcare team can ensure they are getting accurate results that have not been influenced by the antibiotics. This can lead to a more accurate diagnosis and more effective treatment plan.
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