Does probenecid increase tigecycline's half life if so how much?

Short answer: No clinically meaningful increase in tigecycline’s half-life is expected with probenecid.

Why:
- Tigecycline is eliminated mainly by biliary/fecal routes, with only a portion excreted renally (roughly one-third in many sources). Its pharmacokinetic profile is dominated by nonrenal clearance.
- Probenecid inhibits renal organic anion transporters and can raise levels of drugs that are mainly renally cleared, but because tigecycline’s major elimination is nonrenal, the impact on overall clearance and half-life would be small and not well quantified.
- There isn’t robust literature showing a significant or clinically relevant interaction between probenecid and tigecycline, and no dose adjustment for tigecycline is based on renal function.

In practical terms: you shouldn’t expect a meaningful increase in tigecycline’s half-life from probenecid. If both drugs are being used together, monitor the patient as you would normally, but don’t rely on probenecid to modify tigecycline exposure. If you need precise guidance for a specific patient, consult a clinician or a pharmacology reference.