Barbiturates have a low therapeutic index.
How does the nurse interpret this?
Low doses are not therapeutic.
The toxic range is narrow.
They are habit-forming.
The effective, safe dosage range is narrow.
Correct Answer : B,D
Choice A rationale
A low therapeutic index indicates a small difference between the therapeutic dose and the toxic dose, not that low doses are ineffective. The therapeutic index is a ratio that compares the dose that produces a therapeutic effect to the dose that causes toxicity. Therefore, the low end of the dose range can still be therapeutic, but the therapeutic window itself is narrow.
Choice B rationale
Barbiturates have a low therapeutic index, which means there is a narrow margin between the therapeutic and toxic drug concentrations. A small increase in dosage beyond the therapeutic range can lead to significant toxicity. This narrow therapeutic window necessitates close monitoring of patients to avoid adverse effects.
Choice C rationale
While barbiturates are indeed habit-forming and have a high potential for physical and psychological dependence, this characteristic is not what is meant by a "low therapeutic index.”. The low therapeutic index refers to the relationship between the effective dose and the toxic dose, not the potential for addiction.
Choice D rationale
A low therapeutic index signifies that the range between the minimum effective concentration and the minimum toxic concentration is narrow. This means the drug dosage must be carefully controlled and monitored to ensure it is effective without causing harmful side effects. Small dosing errors can lead to toxicity, highlighting the drug's narrow safe dosage range.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is B
Explanation
Choice A rationale
The term hyperthyroidism indicates an overactive thyroid gland, resulting in elevated levels of thyroid hormones, specifically T3 and T4, with a suppressed TSH. This condition leads to an increased metabolic rate, causing symptoms like weight loss, tachycardia, heat intolerance, and anxiety, which is the opposite of the euthyroid state.
Choice B rationale
The term "euthyroid" is a medical state where the thyroid gland is functioning properly and producing the correct amount of thyroid hormones. This means that the patient's serum thyroid-stimulating hormone (TSH), free T4, and free T3 levels are within the normal physiological range (TSH 0.4-4.0 mIU/L, Free T4 0.8-1.8 ng/dL).
Choice C rationale
A fluctuating thyroid hormone level suggests an unstable or untreated thyroid disorder, which would not be described as euthyroid. Euthyroidism implies a state of hormonal stability and equilibrium, where the patient's body has adapted to the medication, and their lab values are consistently within the normal range.
Choice D rationale
An increase in thyroid hormone levels would indicate a transition from a hypothyroid state to a hyperthyroid state. This condition is not referred to as euthyroid, which specifically describes a balanced and normal hormonal level, not an overcorrection or an excessive amount of circulating hormones.
Correct Answer is A
Explanation
Choice A rationale
Chest pain and palpitations in a patient taking levothyroxine can be signs of thyroid hormone overdose or hyperthyroidism, which can induce cardiac side effects. The cardiovascular system is highly sensitive to thyroid hormones. These symptoms could be indicative of myocardial ischemia, tachycardia, or dysrhythmias, which are serious and require immediate medical evaluation. The nurse's priority is to notify the healthcare provider immediately for dose adjustment or further cardiac workup.
Choice B rationale
Advising the patient to rest and monitor symptoms is an insufficient and potentially dangerous action. While rest may temporarily alleviate some symptoms, it does not address the underlying cause, which could be an overdose of the medication. The nurse should not delay notifying the healthcare provider, as the cardiac symptoms could escalate and lead to a more serious event, such as a myocardial infarction.
Choice C rationale
Antacids containing calcium or aluminum can interfere with the absorption of levothyroxine, but they are not a treatment for chest pain or palpitations related to the medication. Administering an antacid would be inappropriate and would not address the patient's serious cardiac symptoms. The nurse's focus should be on addressing the potential cardiac side effects of the medication and reporting them to the healthcare provider.
Choice D rationale
Increasing the dose of levothyroxine would worsen the patient's symptoms. The chest pain and palpitations suggest that the patient may be receiving too high a dose of the thyroid hormone, leading to symptoms of hyperthyroidism. Increasing the dose would further elevate the circulating thyroid hormone levels, exacerbating the cardiac side effects and increasing the risk of a serious cardiac event.
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