Drug Interaction Between Acyclovir and Veozah
No Clinically Significant Interaction Expected
There is no documented drug interaction between acyclovir and Veozah (fezolinetant), and these medications can be safely co-administered without dose adjustment.
Pharmacokinetic Rationale
The absence of interaction is based on the distinct metabolic and elimination pathways of these two drugs:
Acyclovir Disposition
- Acyclovir is primarily eliminated renally through glomerular filtration and tubular secretion, with minimal hepatic metabolism 1.
- Renal clearance accounts for the vast majority of acyclovir elimination, with only one known urinary metabolite: 9-[(carboxymethoxy)methyl]guanine 1.
- The drug shows minimal involvement with cytochrome P450 enzymes or drug transporters that would create interaction potential 2, 3.
Veozah (Fezolinetant) Profile
- Veozah is a neurokinin 3 receptor antagonist used for vasomotor symptoms associated with menopause.
- It does not share metabolic pathways with acyclovir and does not significantly affect renal drug elimination.
- There are no known interactions with renally eliminated drugs.
Critical Clinical Consideration: Renal Function Monitoring
While no direct drug-drug interaction exists, both medications require attention to renal function, particularly when used in patients with pre-existing renal impairment:
Acyclovir in Renal Impairment
- Dosage adjustment is mandatory in patients with reduced renal function to prevent accumulation and potential neurotoxicity 1.
- The half-life and total body clearance of acyclovir are directly dependent on renal function 1.
- Adequate hydration should be maintained to prevent crystalluria and elevated serum creatinine 1, 3.
Risk Amplification with Nephrotoxic Agents
- Caution should be exercised when administering acyclovir to patients receiving potentially nephrotoxic agents, as this may increase the risk of renal dysfunction and/or reversible CNS symptoms 1.
- This concern relates to additive nephrotoxic effects rather than pharmacokinetic drug interactions 1.
Specific Drug Interaction Concerns with Acyclovir
The documented interactions with acyclovir involve different mechanisms than would apply to Veozah:
Mycophenolate Interaction (Relevant Context)
- Mycophenolate can increase plasma concentrations of acyclovir, especially when renal impairment is present 4.
- This interaction occurs through competition for renal tubular secretion, not hepatic metabolism 4.
Probenecid Interaction
- Coadministration of probenecid with acyclovir increases the mean acyclovir half-life and area under the concentration-time curve through reduced urinary excretion and renal clearance 1.
NSAID Combination Risks
- Concomitant use of acyclovir or valacyclovir with NSAIDs has been associated with increased risk of acute kidney injury in post-marketing surveillance data 5.
- This represents an additive nephrotoxic effect rather than a pharmacokinetic interaction 5.
Practical Management Algorithm
For patients requiring both acyclovir and Veozah:
Assess baseline renal function before initiating therapy with either agent 1.
Adjust acyclovir dosing according to creatinine clearance if renal impairment exists (see acyclovir prescribing information for specific adjustments) 1.
Ensure adequate hydration during acyclovir therapy to minimize crystalluria risk 1.
Monitor for acyclovir-related adverse effects including CNS symptoms (confusion, hallucinations, seizures) particularly in elderly patients or those with renal compromise 1.
Continue Veozah at standard dosing without modification, as no interaction mechanism exists.
Common Pitfalls to Avoid
- Do not empirically reduce acyclovir doses based on concern about Veozah co-administration; only adjust for renal function 1.
- Do not overlook age-related renal decline in geriatric patients, as acyclovir plasma concentrations are higher in this population due to reduced renal function 1.
- Do not confuse the absence of drug-drug interaction with the absence of need for renal monitoring; both remain important for acyclovir safety 1.