Phenytoin Adjustment based on Hypoalbuminemia

These equations are for use in patient with Creatinine Clearance of  > 25 ml/min  or  in patients undergoing intermittant dialysis.
For Clearance between 10 and 25  who are not under going dialysis binding afinity is unpredicably altered and calculations cannot be done

 

Enter measured phenytoin  level in mg/liter      

Enter measured albumin level in grams/dl     

Enter clearance in mls/min    

Note:If Albumin is >/=4.4 then measured phenytoin level = corrected phenytoin level

                    
                                                        

Formulas used:

                                                          Clearance >25 non dialysis patient

Phenytoin concentrtion               Measured Phenytoin concentration (mg/liter)
normal Plasma Binding   =          [0.9 * Patients Serum albumin] + 0.1
                                                                    4.4 gm/dl

                                                                 Dialysis patient 

Phenytoin concentrtion               Measured Phenytoin concentration (mg/liter)
normal Plasma Binding   =          [(0.9)(0.48) * Patients Serum albumin] + 0.1
&                                                                    4.4 gm/dl

More phenytoin calculations:  GlobalRPh

 

Dosage adjustments

For levels less than 7 consider increase by 100mg daily
For levels 8-11 consider increase by 50mg daily
For levels 12 and greater increase in 30mg increments daily

Updated 3/6/08    Chris Chambers, Pharm D

Reference: Basic Clinical Pharmacokinetics Fourth edition Michael E. Winter