What precaution should be kept in mind while administering phenytoin?

Appeared in: NIMHANS Nursing Officer - 2021

Explanation

The maximum safe rate for IV phenytoin administration in adults is 50 mg per minute.
Infusing phenytoin faster than this rate can cause severe cardiovascular complications, including hypotension, bradycardia, and life-threatening arrhythmias.
This precaution is critical to prevent cardiac depression, which is caused by both the drug itself and its solvent, propylene glycol.
Continuous cardiac and blood pressure monitoring is mandatory during the infusion.

Option B: This option uses the wrong unit (mcg instead of mg). A rate of 50 micrograms per minute would be a significant underdose and therapeutically ineffective.
Option C: While 25 mg/min is a safer rate and often used for geriatric patients or those with cardiac instability, it is not the maximum precautionary limit. The absolute maximum rate that should not be exceeded is 50 mg/min.
Option D: This option is incorrect due to both the numerical value and the unit (mcg). It represents an extremely low, subtherapeutic dose.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Safe administration of IV phenytoin as background academic context rather than a clinical decision trigger.
Patient safety is paramount. Exceeding the 50 mg/min infusion rate for IV phenytoin can lead to iatrogenic cardiac arrest. Nurses must be vigilant and always use an infusion pump for precise rate control.
This is a common medication used in emergency settings for status epilepticus. Knowing the correct administration protocol is a critical nursing competency.
What if? If the patient is elderly or has a history of heart disease, the infusion rate should be reduced to 25 mg/min or even slower, and an alternative like fosphenytoin (which can be infused faster with fewer cardiac effects) should be considered.

How to Approach the Question

First, identify the core of the question: it's asking for a specific safety precaution related to the IV administration of the drug phenytoin.
Recognize that questions about IV medication rates, especially for high-risk drugs like phenytoin, are testing critical safety knowledge.
Differentiate between the units 'mg' (milligrams) and 'mcg' (micrograms). Phenytoin is dosed in mg, so options with 'mcg' can be immediately identified as incorrect.
Between the remaining 'mg' options, recall the standard maximum infusion rate for adults. The key is to remember the upper limit that must not be exceeded to prevent adverse events.
Select the option that states the correct maximum rate (50 mg/min) as the essential precaution.

Concept Tested & Keywords

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E6 Pharmacology Nursing Lilley 11e Part 1 pp. 242-244, 241-243

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