Total Serum Valproic Acid (VPA) Concentration & Low Albumin Level.

 

 


Total VPA levels monitoring in patients with low albumin level may not represent correct VPA level.

 

Hermida et al published this study on finding a theoretical equation for normalizing total Serum Valproic Acid Concentration in hypoalbuminemic Patients. This post is a brief summary of this equation. Share your experiences if you use this equation in your clinical practice.

 


STEP 1: CALCULATE FREE FRACTION OF VPA (α).

 

IN PATIENTS WITH LOW ALBUMIN:

αh = Cf/Ch

Cf = Free VPA concentration.
Ch = Total VPA concentration.

 

IN PATIENTS WITH NORMAL ALBUMIN:

αn = Cf/Cn

Cf = Free VPA concentration.
Cn = Total Normalized VPA level.

 


STEP 2: EQUATION

 

Based on above two equations:

 

αn X Cn = αh X Ch

Cn = αh X Ch/ αn

 

 

Cn = αh X Ch/ αn

This equation will work for patients with normal albumin level.

 

Cn = αh X Ch/ αc

This equation will work for patients with low albumin level.

αh: Free fraction of VPA.

Ch: Total VPA concentration.

αc: see Step 3 for details.

 


STEP 3:  CALCULATING αc BASED ON PATIENT’S LOW ALBUMIN

 

ALBUMIN (g/L)

αc

42

6.5

41

6.8

40

7.3

39

7.9

38

8.5

37

9.1

36

9.8

35

10.5

34

11.3

33

12.1

32

13

31

14

30

15

29

16.2

28

17.4

27

18.7

26

20.1

25

21.6
24

23.2

23

24.9

22

26.8

21

28.9

20

31
19

33.3

18

35.8

 


SOURCE:

 

  • J Pharmacol Sci 97, 489 – 493 (2005).

Please do post your questions or comments below. 


Dr. Harvinder Singh, M.D. (Admin)


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