Drugs That Increase Acyclovir Levels
Acyclovir is primarily cleared by the kidneys, so drugs that reduce renal function can raise its blood levels, increasing toxicity risks like kidney damage or neurological effects. Probenecid blocks renal tubular secretion of acyclovir, prolonging its half-life by up to 50%.[1]
Common examples:
- Probenecid (used for gout).
- Nephrotoxic drugs: Aminoglycosides (e.g., gentamicin), amphotericin B, cyclosporine, tacrolimus, methotrexate, foscarnet, cidofovir, and high-dose IV pentamidine. These combinations demand dose adjustments and close monitoring of kidney function and acyclovir levels.[2][3]
Drugs Affected by Acyclovir
Acyclovir has minimal direct effects on other drugs' metabolism via CYP enzymes, but its nephrotoxicity can indirectly impair clearance of renally excreted medications.[3]
Notable cases:
- Mycophenolate mofetil: Acyclovir may increase its exposure; monitor for immunosuppression side effects.
- Zidovudine (AZT): Concurrent use has caused increased drowsiness and lethargy in some HIV patients.[1][2]
Risk of Kidney Damage from Combinations
Multiple drugs amplify acyclovir's risk of acute kidney injury, especially with IV administration or dehydration. Avoid or use cautiously with:
- Nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen.
- Contrast dyes (e.g., for CT scans).
- Loop diuretics (e.g., furosemide) in high doses.[3]
Hydration and serial creatinine checks are standard precautions.
No Major Interactions in These Categories
Acyclovir shows no clinically significant interactions with:
- Oral contraceptives.
- Antacids or cimetidine (unlike related drugs like valacyclovir).
- Warfarin or theophylline.[1][2]
Always check patient-specific factors like age, hydration, and renal baseline.
[1] Drugs.com - Acyclovir Interactions
[2] Medscape - Acyclovir Drug Interactions
[3] Lexicomp - Acyclovir Monograph