Ibuprofen Serum Levels in Overdosage

 

Adverse effects seen in overdosage situations:

(1) central nervous system depression

(2) seizures

(3) gastrointestinal tract disturbances

(4) bradycardia and/or hypotension

(5) apnea

(6) abnormal renal function

(7) hematuria

(8) nystagmus and/or blurred vision

 

A nomogram (page 1309) can be used to determine if the serum level seen is "probably", "possibly", or "unlikely" to be associated with toxicity. Estimates for values along the lines separating these regions are as follows:

 

time since ingestion	lower line (unlikely vs possible toxicity)	upper line (possible vs probable toxicity)
1 hour	100 µg/mL	208 µg/mL
4 hours	66 µg/mL	142 µg/mL
6 hours	51 µg/mL	105 µg/mL
11 hours	28 µg/mL	57 µg/mL

 

Since the nomogram is semilog (linear time axis, log10 y-axis) and the plots are linear and parallel:

 

slope of both lines =

= (LOG10(serum level at time 2) - LOG10 (serum level at time 1)) / ((time 2) - (time 1)

 

If the data is examined, the slope is approximately (-0.056).

 

intercept at 1 hour post ingestion =

= LOG10(serum level at 1 hour)

 

For the upper line, the intercept is LOG10(208) = 2.318; for the lower line, the intercept is LOG10(100) = 2.

 

serum level defining interpretive breakpoint =

= 10^((LOG10(serum level at 1 hour)) - (0.056 * ((hours since ingestion) - 1)))

 

equation describing levels determining probable toxicity =

= 10^((2.318 - (0.056 * ((hours since ingestion) - 1)))

 

equation describing level determining possible toxicity =

= 10^((2 - (0.056 * ((hours since ingestion) - 1)))

 

Notes:

• Serum levels drawn < 1 hour after ingestion may be misleading due to inadequate absorption and distribution.

• The nomogram covers only the period of 1-12 hours after ingestion.