Dilantin® Jeopardy: Avoiding The Dangers of Phenytoin

MedSurg Nursing, Dec, 1998 by Michael L. Schlicher

The physician in the scenario ordered a phenytoin drip. Nurses must understand how to prepare and administer the drip safely. Based partly on the fact that phenytoin lacks solubility and tends to precipitate in solution, most nurses have been told never to use phenytoin as a drip. As a result, there is little information available regarding drip procedures and rates. However, it is possible that if diluted correctly, administration via continuous infusion is safe (Trissel, 1992).

To prepare a drip, the drug is diluted to a 1:1 concentration. For example, 250 mg of phenytoin is mixed with 250 ml of normal saline. Only use normal saline to avoid possible precipitation, and use a micron in-line filter just as a precaution. The drip should be infused over 2 to 4 hours yet should not exceed the basic rule of 50 mg/min (Vallerand & Deglin, 1994). Always inspect the solution closely for possible crystalline formation. A faint yellow color is normal and won't affect potency. The IV site should be checked frequently for any signs of extravasation, in which case you should stop the infusion immediately, remove the IV, and cover the area with a sterile dressing. Apply cold compresses and elevate the extremity. Then call the patient's physician and document your findings and action taken (see Tables 2 & 3).

Table 2.

Best Nursing Interventions to Avoid Phenytoin Extravasation

1. Use appropriate phenytoin dose and rate of administration.

2. Take time to make proper placement and location of IV sites (avoiding small veins and poor venous circulation areas).

3. Make sure to flush IV with saline before and after a direct injection.

4. Administer the medication slowly, no greater than 50 mg/min (in adults).

5. Splint extremity while an IV cannula is in place to avoid excessive movement.

6. Frequently monitor the solution of phenytoin for precipitation as well as your patient for any adverse effects.

7. Use transparent dressing and clear tape to allow frequent inspection of injection site.

8. Remember the best treatment is always prevention.

Table 3.

Calculation Examples for Phenytoin

1. Doctor orders a loading dose of 15 mg/kg IV push for your patient who weighs 70 k. You have available 250 mg in 5 cc vials.

70 k x 15 mg = 1,050 mg

(You will need 4 1/2 vials to obtain the total amount of drug)

(You are aware that you can only give 50 mg/min.

(1,050 divided by 50 mg = 21 minutes for administration of dose.

(Load your infusion pump syringe with the 1,050 mg. You will need a 30 cc syringe. You set the infusion pump for 21 rains in order to infuse the total amount correctly.

2. For some reason your patient will be going to surgery and the surgeon has ordered a phenytoin drip of 250 mg/hr. Here's how you would set it up.

(Make your concentration 1:1 as follows.

(Take 500 mg of phenytoin and mix it in 500 ml of NS.

(Check for any crystal formations as a safeguard.

(You would then set your pump to 250 cc/hr knowing that your patient would only be getting 4.16 mg/min which is well within your guidelines for adult administration. Mark the bag carefully, document carefully, and double check any calculations with another nurse or the pharmacy. Keep in mind patient's fluid status and remember to mark line so that no other drugs are given through this infusion. Also, make sure line has a filter on it. You will have 2 hours of infusion at the desired rate.