Recommended adjustment based on trough concentration:
Trough
concentration
|
Daily dose
|
Frequency
Preferred
|
Increase_by_50-75%__Increase'>Example
|
<5 mg/L
|
Increase by 50-75%
|
Increase
|
Current daily dose X 1.5-1.75 = NEW DAILY DOSE
|
5-9.9 mg/L
|
Increase by 25-50%
|
Increase
|
Current daily dose X 1.25-1.5 = NEW DAILY DOSE
|
10-20 mg/L
|
No Change
|
-
|
-
|
20.1-30 mg/L
|
Decrease by 10-30%
|
Decrease
|
Current daily dose X 0.9-0.7 = NEW DAILY DOSE
|
>30 mg/L
|
WITHOLD DOSE
|
|
|
Repeat trough level 24 hourly until concentration 10-20mg/L
|
Decrease
|
Current daily dose X 0.5 = NEW DAILY DOSE
|
Changing frequency of administration is preferred against changing dose.
< 5 mg/L − increase total daily dose by 50–75% (i.e. 1.5-1.75 times)) by either increasing frequency (preferred) or increasing each dose.
5–9.9 mg/L − increase total daily dose by 25–50% (i.e. 1.25-1.5 times) by either increasing frequency (preferred) or increasing each dose.
10–20 mg/L − no change in dose required.
20.1–30 mg/L − decrease total daily dose by 10–30% (i.e. 0.9-0.7 times) by decreasing frequency (preferred) or decreasing each dose.
> 30 mg/L − withhold dose. Repeat trough concentration 24 hourly until plasma concentration is 10–20 mg/L, then restart at a dose decreased by 50% (i.e. 0.5 times) by decreasing frequency (preferred) or decreasing each dose.
Example for adjusting dose by increasing / decreasing frequency:
Calculate current total daily dose (e.g. 15 mg 8 hourly = 45 mg/day).
If trough <5 mg/L – Increase total daily dose by 1.5 times (i.e. 45 x 1.5 = 67.5 mg/day) and decide on achieving this total daily dose by either increasing the frequency or increasing the dose. :
If trough 20.1–30 mg/L - Decrease total daily dose to 0.7 times (i.e. 45 x 0.7 = 31.5 mg/day) and decide on achieving this total daily dose by either decreasing the frequency or decreasing the dose.
| 