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Valacyclovir hydrochloride and Encephalitis - a phase IV clinical study of FDA data

Summary:

Encephalitis is reported as a side effect among people who take Valacyclovir hydrochloride (valacyclovir hydrochloride), especially for people who are female, 60+ old, have been taking the drug for < 1 month also take Bactrim, and have Chronic lymphocytic leukaemia.

The phase IV clinical study analyzes which people have Encephalitis when taking Valacyclovir hydrochloride. It is created by eHealthMe based on reports of 12,770 people who have side effects when taking Valacyclovir hydrochloride from the FDA, and is updated regularly.

What is Valacyclovir hydrochloride?

Valacyclovir hydrochloride has active ingredients of valacyclovir hydrochloride. It is often used in herpes zoster. eHealthMe is studying from 12,929 Valacyclovir hydrochloride users. Check the latest studies of Valacyclovir hydrochloride.

What is Encephalitis?

Encephalitis (inflammation of the brain) is found to be associated with 655 drugs and 847 conditions by eHealthMe. Check the latest studies of Encephalitis.

eHealthMe: drug outcomes in the real world

eHealthMe runs one of the largest post-marketing drug safety studies in the world. We study millions of patients and 5,000 more each day. Our data-driven phase IV clinical trials have been referenced on 800+ peer-reviewed medical publications including The Lancet, Mayo Clinic Proceedings, and Nature. Tools to study our phase IV findings are available to the public, anonymous and free >>>.

On Aug, 31, 2026

12,770 people reported to have side effects when taking Valacyclovir hydrochloride.
Among them, 26 people (0.2%) have Encephalitis.

Could Valacyclovir hydrochloride cause Encephalitis?

Among these 26 people:

How long have people been on Valacyclovir hydrochloride when they have Encephalitis? *

  • < 1 month: 100 %
  • 1 - 6 months: 0.0 %
  • 6 - 12 months: 0.0 %
  • 1 - 2 years: 0.0 %
  • 2 - 5 years: 0.0 %
  • 5 - 10 years: 0.0 %
  • 10+ years: 0.0 %

What is the gender of people who have Encephalitis when taking Valacyclovir hydrochloride? *

  • female: 52.17 %
  • male: 47.83 %

What is the age of people who have Encephalitis when taking Valacyclovir hydrochloride? *

  • 0-1: 0.0 %
  • 2-9: 0.0 %
  • 10-19: 0.0 %
  • 20-29: 0.0 %
  • 30-39: 20 %
  • 40-49: 20 %
  • 50-59: 0.0 %
  • 60+: 60 %

What are other drugs people take besides Valacyclovir hydrochloride? *

  1. Bactrim: 6 people, 23.08%
  2. Dexamethasone: 5 people, 19.23%
  3. Acyclovir: 4 people, 15.38%
  4. Acetaminophen: 3 people, 11.54%
  5. Fluconazole: 3 people, 11.54%
  6. Oncovin: 3 people, 11.54%
  7. Amoxicillin: 3 people, 11.54%
  8. Pantoprazole: 3 people, 11.54%
  9. Cytarabine: 3 people, 11.54%
  10. Pomalidomide: 3 people, 11.54%

What are other side effects people have besides Encephalitis? *

  1. Hemiplegia (paralysis of one side of the body): 2 people, 7.69%
  2. Optic Neuritis (optic nerve inflammation): 2 people, 7.69%
  3. Headache (pain in head): 2 people, 7.69%
  4. Fever: 2 people, 7.69%
  5. Epilepsy (common and diverse set of chronic neurological disorders characterized by seizures): 2 people, 7.69%
  6. Dyspnea (difficult or laboured breathing): 2 people, 7.69%
  7. Drug Ineffective: 2 people, 7.69%
  8. Meningitis Aseptic (a condition that causes the membranes covering your brain and spinal cord to become inflamed): 2 people, 7.69%
  9. Cytokine Release Syndrome (immediate complication occurring with the use of anti-t cell antibody infusions): 2 people, 7.69%
  10. Confusional State: 2 people, 7.69%

What are the existing conditions these people have? *

  1. Multiple Myeloma (cancer of the plasma cells): 3 people, 11.54%
  2. Chronic Lymphocytic Leukaemia (cancer in which the bone marrow makes too many lymphocytes (a type of white blood cell)): 3 people, 11.54%
  3. Hodgkin's Lymphoma (cancer originating from white blood cells): 2 people, 7.69%
  4. Acute Lymphocytic Leukemia (All) (cancer of the white blood cells characterized by excess lymphoblasts): 2 people, 7.69%
  5. Mantle Cell Lymphoma (cancer of lymphocytes, a type of white blood cell): 2 people, 7.69%
  6. Graft Versus Host Disease In Skin (the donated bone marrow or stem cells view the recipient's body as foreign, and the donated cells/bone marrow attack the skin): 1 person, 3.85%
  7. Acanthamoeba Infection (acanthamoeba infection is a cutaneous condition): 1 person, 3.85%
  8. Bone Marrow Conditioning Regimen: 1 person, 3.85%
  9. Epilepsy (common and diverse set of chronic neurological disorders characterized by seizures): 1 person, 3.85%
  10. Graft Versus Host Disease (the donated bone marrow or stem cells view the recipient's body as foreign, and the donated cells/bone marrow attack the body): 1 person, 3.85%

* Approximation only. Some reports may have incomplete information.

Do you take Valacyclovir hydrochloride and have Encephalitis?

- Check whether Encephalitis is associated with a drug or a condition
- Predict drug outcomes for up to one year with AI
- Get an AI agent to monitor your drugs continuously

Related studies:

Effectiveness of, long term effects of, and alternative drugs to Valacyclovir hydrochloride:

Encephalitis treatments and more:

How severe was Encephalitis and when was it recovered:

Expand to all the drugs that have ingredients of valacyclovir hydrochloride:

Sub-studies by gender and age:

Female: 0-1 2-9 10-19 20-29 30-39 40-49 50-59 60+

Male: 0-1 2-9 10-19 20-29 30-39 40-49 50-59 60+

Browse all side effects of Valacyclovir hydrochloride:

a b c d e f g h i j k l m n o p q r s t u v w x y z

Browse all the drugs that are associated with Encephalitis:

Browse all the conditions that are associated with Encephalitis:

How the study uses the data?

The study uses data from the FDA. It is based on valacyclovir hydrochloride (the active ingredients of Valacyclovir hydrochloride) and Valacyclovir hydrochloride (the brand name). Other drugs that have the same active ingredients (e.g. generic drugs) are not considered. Dosage of drugs is not considered in the study.

How to use the study?

DO NOT STOP MEDICATIONS without first consulting your doctor. If there are any serious or long term adverse effects discovered in the study, discuss the study with your doctor to ensure that proper medication management will be in place if applicable.

Who is eHealthMe?

With medical big data and proven AI/ML algorithms, eHealthMe provides a platform for everyone to run phase IV clinical trials. We study millions of patients and 5,000 more each day. Results of our real-world drug study have been referenced on 800+ peer-reviewed medical publications, including The Lancet, Mayo Clinic Proceedings, and Nature. Our analysis results are available to researchers, health care professionals, patients (testimonials), and software developers (open API).

WARNING, DISCLAIMER, USE FOR PUBLICATION

WARNING: Please DO NOT STOP MEDICATIONS without first consulting a physician since doing so could be hazardous to your health.

DISCLAIMER: All material available on eHealthMe.com is for informational purposes only, and is not a substitute for medical advice, diagnosis, or treatment provided by a qualified healthcare provider. All information is observation-only. Our phase IV clinical studies alone cannot establish cause-effect relationship. Different individuals may respond to medication in different ways. Every effort has been made to ensure that all information is accurate, up-to-date, and complete, but no guarantee is made to that effect. The use of the eHealthMe site and its content is at your own risk.

If you use this eHealthMe study on publication, please acknowledge it with a citation: study title, URL, accessed date.

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