What precaution should be kept in mind while administering phenytoin?

NORCET -4 , 2023

Pharmacology

Easy

Appeared in: NORCET -4 , 2023

Explanation

The standard maximum rate for intravenous phenytoin administration in adults is 50 mg per minute.
This rate limit is a critical safety measure to prevent severe cardiovascular complications.
Exceeding this rate can lead to life-threatening hypotension (low blood pressure) and cardiac arrhythmias (irregular heartbeats).
The risk is associated with both the drug and its diluent, propylene glycol, which can depress the myocardium.

Option A: The unit 'mcg' (micrograms) is incorrect. Phenytoin IV doses are measured in 'mg' (milligrams). This option represents a thousand-fold underdose and an incorrect unit.
Option B: While a rate of 25 mg per minute is used for certain high-risk populations (e.g., elderly, patients with cardiac disease), it is not the standard maximum rate for the general adult population. The question asks for the general precaution, which refers to the upper limit.
Option C: The unit 'mcg' (micrograms) is incorrect. Phenytoin IV doses are measured in 'mg' (milligrams).

Visual 1: Infographic - 'Phenytoin IV Administration Safety Checklist'. This could show key points like 'Max Rate: 50 mg/min', 'NS Only', 'Use Filter', 'Monitor ECG & BP', and 'Large Vein Access'.
Visual 2: Diagram - 'Purple Glove Syndrome'. A visual showing the signs of phenytoin extravasation, such as discoloration, edema, and pain in the hand and arm, to emphasize the importance of correct IV site selection and monitoring.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Pharmacology: Safe IV Administration of High-Risk Medications as background academic context rather than a clinical decision trigger.
A nurse's primary role during phenytoin infusion is patient safety, which involves strict adherence to the administration rate and continuous monitoring of vital signs and ECG.
Recognizing early signs of toxicity, such as a drop in blood pressure or changes in heart rhythm, allows the nurse to stop the infusion immediately and prevent a catastrophic event.
What if the patient is receiving phenytoin and their blood pressure drops from 120/80 mmHg to 90/50 mmHg? The nurse's immediate action should be to stop the infusion, notify the physician, and prepare to administer supportive care as ordered. This demonstrates the critical need for vigilant monitoring.

How to Approach the Question

First, identify the core of the question: it's asking for a safety precaution related to administering the drug phenytoin.
Analyze the options. Notice they all concern the rate of IV administration and differ in two ways: the numerical value (25 vs. 50) and the unit (mcg vs. mg).
Immediately eliminate the options with 'mcg' (micrograms). High-risk IV drugs like phenytoin are dosed in milligrams, not micrograms, for this purpose. This rules out options A and C.
Now, differentiate between the remaining options: 25 mg/minute and 50 mg/minute.
Recall or deduce the standard maximum infusion rate for phenytoin in adults. The established guideline is not to exceed 50 mg/minute to prevent cardiotoxicity.
Therefore, select the option stating that the IV administration rate should not exceed 50 mg per minute.

Concept Tested & Keywords

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