Pharmacobezoars (clumps of medication/pills) formation has been demonstrated in few medications such as aspirin, and ferrous sulfate tablets. Their presence can alter management due to prolonged absorption and may cause GI obstruction.

Acetaminophen (APAP) is a commonly available over-the-counter medication that is often implicated in an acute overdose event. A recently published in-vitro study (using pig stomach) investigated whether APAP can form a pharmacobezoar.

APAP group/dosage

• 25 gm (50 tablets)
• 37.5 gm (75 tablets)
• 50 gm (100 tablets)

Positive control group

• ferrous sulfate (15 gm/50 tablets)

Negative control group

• chlorpheniramine (200 mg (50 tablets)

Results

• APAP formed clumps in 37.5 gm and 50 gm groups
• 83% (5 out of 6) of the 25 gm APAP group did not form clumps.

• Dissolution profile: APAP clumps released more slowly (over 60 min tested) compared to individual tablet without reaching a peak.

Conclusion

• APAP can form pharmacobezoar at doses greater than 37.5 gm (in-vitro model) and can result in prolonged or delayed toxicity due to pharmacobezoar formation.

References

Li YK et al. In vitro study of pharmacobezoar formation in simulated acetaminophen overdose. Clin Toxicol (Phila) 2019. https://doi.org/10.1080/15563650.2019.1705971