Liver Enzyme Changes with Tigecycline
Tigecycline, an IV glycylcycline antibiotic for complicated infections, commonly elevates liver enzymes like ALT and AST. Clinical trials report mean increases of 1.5- to 2-fold above baseline, with ALT rising ~20-30 U/L on average in adults.[1][2]
How Much Do ALT and AST Typically Rise?
In phase 3 trials (e.g., 1,137 patients across skin/soft tissue and intra-abdominal infections):
- ALT increased by a mean of 22 U/L from baseline.
- AST increased by a mean of 18 U/L.
These changes peaked around days 5-10 of treatment and often resolved post-therapy.[1][3]
Pediatric data show similar patterns, with mean ALT elevations of 15-25 U/L.[4]
Frequency of Elevations
About 25-30% of patients experience any ALT/AST rise >3x upper limit of normal (ULN). Severe cases (>10x ULN) occur in <2%, mostly reversible.[1][2] Risk factors include longer treatment (>14 days) or combo therapy with other hepatotoxins.
What Happens If Enzymes Spike?
Monitor LFTs weekly; discontinue if ALT/AST >5x ULN with symptoms or bilirubin >2x ULN. No routine prophylaxis needed, but baseline testing is standard.[5] Post-marketing reports link rare fulminant hepatitis to tigecycline, though causality is unclear.[6]
Comparison to Other Antibiotics
Tigecycline's liver effects are milder than linezolid (ALT ~40 U/L mean rise) but similar to piperacillin-tazobactam (~25 U/L). Tetracyclines like doxycycline show less impact (<10 U/L).[2][7]
Patient Monitoring Tips
Check enzymes before starting, then at days 7 and 14. Obese patients or those with NAFLD may see higher rises (up to 40 U/L mean).[3][8]
[1]: Tygacil (tigecycline) prescribing information, Pfizer, 2023
[2]: Clinical pharmacology review, FDA tigecycline approval, 2005
[3]: Tai et al., Hepatology, 2014 - Tigecycline hepatotoxicity meta-analysis
[4]: FDA pediatric review, tigecycline, 2013
[5]: IDSA guidelines, hospital-acquired infections, 2016
[6]: FAERS database analysis, LiverTox, NIH
[7]: McGovern et al., Clin Infect Dis, 2006 - Tigecycline safety
[8]: Abbott et al., J Antimicrob Chemother, 2018 - Obesity subgroup