Acyclovir with Valproic Acid Interaction Details

Brand Names Associated with Acyclovir

Brand Names Associated with Valproic Acid

Medical Content Editor Dr. Brian Staiger, PharmD
Last updated Feb 26, 2024

Interaction Effect

Decreased valproic acid plasma concentrations and potential increased seizure activity

Interaction Summary

A case report from the University of Bologna in Italy documents a reduction in plasma levels of both phenytoin and valproic acid when combined with acyclovir treatment. This reduction resulted in increased seizure activity from approximately one per month to 25 in one day. Phenytoin dosage was increased and plasma levels returned to therapeutic ranges after 10 days[1].

Severity

Moderate

Onset

Delayed

Evidence

Probable

How To Manage Interaction

Monitor patients for reduction in antiepileptic plasma levels. Consider alternative antiviral therapy.

Mechanism Of Interaction

Increased gastrointestinal transit or change in gastrointestinal fluid pH

Literature Reports

A) A seven-year-old child with a history of epilepsy experienced increased seizure activity after being treated with acyclovir in addition to his antiepileptic medications. The patient's trough plasma levels of phenytoin and valproic acid were 17 and 32 mcg/mL, respectively, 10 days before starting acyclovir treatment for viral throat and mouth lesions. Four days after initiation of acyclovir treatment, the trough levels were 5.0 and 22 mcg/mL, respectively. Acyclovir treatment was discontinued after six days. Three and six days after acyclovir withdrawal, phenytoin and valproic acid plasma levels were still low, and the patient experienced 25 serial partial seizures five days after discontinuation. Phenytoin dosage was increased to reach therapeutic plasma levels and the frequency of seizures was reduced to two or three per week. The authors suggest that further study of this possible interaction is warranted [1].

References

1 ) Parmeggiani A, Riva R, Posar A, et al: Possible interaction between acyclovir and antiepileptic treatment. Ther Drug Monit 1995; 17:312-315.

Acyclovir Overview

• Acyclovir is used to decrease pain and speed the healing of sores or blisters in people who have varicella (chickenpox), herpes zoster (shingles; a rash that can occur in people who have had chickenpox in the past), and first-time or repeat outbreaks of genital herpes (a herpes virus infection that causes sores to form around the genitals and rectum from time to time). Acyclovir is also sometimes used to prevent outbreaks of genital herpes in people who are infected with the virus. Acyclovir is in a class of antiviral medications called synthetic nucleoside analogues. It works by stopping the spread of the herpes virus in the body. Acyclovir will not cure genital herpes and may not stop the spread of genital herpes to other people.

Valproic Acid Overview

• Valproic acid is used alone or with other medications to treat certain types of seizures. Valproic acid is also used to treat mania (episodes of frenzied, abnormally excited mood) in people with bipolar disorder (manic-depressive disorder; a disease that causes episodes of depression, episodes of mania, and other abnormal moods). It is also used to prevent migraine headaches but not to relieve headaches that have already begun. Valproic acid is in a class of medications called anticonvulsants. It works by increasing the amount of a certain natural substance in the brain.

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Definitions

Severity Categories

Contraindicated

These drugs, generally, should not be used together simultaneously due to the high risk of severe adverse effects. Combining these medications can lead to dangerous health outcomes and should be strictly avoided unless otherwise instructed by your provider.

Major

This interaction could result in very serious and potentially life-threatening consequences. If you are taking this drug combination, it is very important to be under close medical supervision to minimize severe side effects and ensure your safety. It may be necessary to change a medication or dosage to prevent harm.

Moderate

This interaction has the potential to worsen your medical condition or alter the effectiveness of your treatment. It's important that you are monitored closely and you potentially may need to make adjustments in your treatment plan or drug dosage to maintain optimal health.

Minor

While this interaction is unlikely to cause significant problems, it could intensify side effects or reduce the effectiveness of one or both medications. Monitoring for changes in symptoms and your condition is recommended, and adjustments may be made if needed to manage any increased or more pronounced side effects.

Onset

Rapid: Onset of drug interaction typically occurs within 24 hours of co-administration.

Delayed: Onset of drug interaction typically occurs more than 24 hours after co-administration.

Evidence

Level of documentation of the interaction.

Established: The interaction is documented and substantiated in peer-reviewed medical literature.

Theoretical: This interaction is not fully supported by current medical evidence or well-documented sources, but it is based on known drug mechanisms, drug effects, and other relevant information.

How To Manage The Interaction

Provides a detailed discussion on how patients and clinicians can approach the identified drug interaction as well as offers guidance on what to expect and strategies to potentially mitigate the effects of the interaction. This may include recommendations on adjusting medication dosages, altering the timing of drug administration, or closely monitoring for specific symptoms.

It's important to note that all medical situations are unique, and management approaches should be tailored to individual circumstances. Patients should always consult their healthcare provider for personalized advice and guidance on managing drug interactions effectively.

Mechanism Of Interaction

The theorized or clinically determined reason (i.e., mechanism) why the drug-drug interaction occurs.

Disclaimer: The information provided on this page is for informational purposes only and should not be considered medical advice. Always consult with a qualified healthcare professional regarding your specific circumstances and medical conditions.

Where Does Our Information Come From?

Information for our drug interactions is compiled from several drug compendia, including:

• Gold Standard Drug Database
• Micromedex
• Lexicomp
• DrugBank

The prescribing information for each drug, as published on DailyMED, is also used. 

Individual drug-drug interaction detail pages contain references specific to that interaction. You can click on the reference number within brackets '[]' to see what reference was utilized.

The information posted is fact-checked by HelloPharmacist clinicians and reviewed quarterly.