The presence of hypoalbuminemia is known to reduce the protein binding of phenytoin in plasma,8,10 and both the ratio of free/total phenytoin concentration and the total phenytoin concentration may be altered.
How do you adjust phenytoin levels?
If the phenytoin concentration is 7-12 mcg/mL, the dose may be increased by 50 mg/day. If the phenytoin concentration is >12 mcg/mL, the dose may be increased by 30 mg/day. If the phenytoin concentration is >16 mcg/mL, any change may result in a significant increase in serum level and should be done very carefully.
How do you calculate phenytoin correction?
If clcr < 20 mL/min then Corrected Phenytoin = Total Phenytoin Level / ( (0.1 x albumin) + 0.1) This is so cool!
When to obtain phenytoin level?
Administration of phenytoin and interpretation of serum phenytoin levels vary depending on the clinical scenario. Loading doses to achieve rapid therapeutic levels should be checked 1 hour after an intravenous loading dose and 24 hours after an oral loading dose.
When to check phenytoin levels?
It may be ordered every few days when a person first begins taking phenytoin to help adjust the dose to the desired blood level. The test is then ordered at regular intervals and as needed to monitor blood concentrations.
What are appropriate phenytoin levels?
These patients also tend to have low serum albumin. In general, aim for therapeutic levels between 20-40 umol/L. D. DOSAGE ADJUSTMENT Phenytoin does NOT demonstrate a proportional relationship between drug levels and dose. Due to zero order kinetics, dosage should NOT be increased by more than 50-100mg increments.
How to dose adjust phenytoin?
The steep relationship between phenytoin concentration and dose indicates that when the concentration reaches 5-10 μg/ml it is then appropriate to adjust dose by small steps of about 25 mg.
