How Probenecid Increases Tigecycline Exposure
Probenecid inhibits organic anion transporters (OATs), particularly OAT3 in the kidneys, which reduces tigecycline's active secretion into urine. Tigecycline, a glycylcycline antibiotic, undergoes minimal renal clearance (about 15-20% unchanged), but its renal secretion contributes to overall elimination. By blocking this pathway, probenecid decreases tigecycline clearance, raising plasma concentrations and prolonging exposure (AUC).
Key Pharmacokinetic Changes from Studies
Clinical studies show probenecid roughly doubles tigecycline's exposure:
- AUC increases by 1.5- to 2-fold.
- Half-life extends from ~42 hours to ~60 hours.
- Peak plasma concentration (Cmax) rises modestly (20-30%).
- Renal clearance drops by 50-70%, with no change in non-renal clearance.
A study in healthy volunteers (200 mg tigecycline IV + 2 g probenecid orally) confirmed these effects, attributing them to OAT3 inhibition at the proximal tubule.[1] Tigecycline's biliary excretion (59%) remains unaffected, as probenecid's impact is kidney-specific.
Clinical Implications and Dosing Adjustments
Elevated tigecycline levels from probenecid may enhance efficacy against resistant infections but heighten risks like nausea, vomiting, or pancreatitis. No routine dose adjustments are FDA-recommended, but monitoring is advised in renal impairment or when co-administered. Probenecid is sometimes used off-label to boost tigecycline in critically ill patients with subtherapeutic levels.[2]
Comparison to Other Drug Interactions
Unlike CYP450 inducers (e.g., rifampin, which lowers tigecycline AUC by 40%), probenecid's effect is transporter-mediated and additive with warfarin (also OAT-inhibited). No significant interaction with colistin or vancomycin, common tigecycline combo partners.[3]
Sources
[1]: PubMed - Probenecid-tigecycline interaction study
[2]: FDA Tigecycline Label
[3]: Clinical Pharmacology & Therapeutics review