Drug & supplement interaction

St. John's Wort + Valacyclovir

Valacyclovir brand name: Valtrex.

No Known Interaction

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS · Updated July 2026 · Pair last verified Sep 13, 2026

The bottom line No known interaction

We found no known interaction between St. John's Wort and Valacyclovir in our sources. Absence of a documented interaction is not the same as proven safety, and does not guarantee one does not exist. Do not start, stop, or change a medication or supplement based on this page; confirm with your pharmacist or doctor first. Additionally, although there is no interaction, the two are separately associated with some of the same side effects, which would make a new symptom harder to attribute to one or the other.

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Interaction report

St. John's Wort and Valacyclovir

We checked these two against our interaction database. Here is what we found.

No Known Interaction Found

We did not find a documented interaction between Valacyclovir and St. John's Wort in our sources. This does not guarantee that the combination is completely free of risk — there is often limited research on supplements and herbal products, especially around drug interactions.

If you decide to take both, the practical routine is simple: add one new thing at a time and note the date you started it. If the combination is going to disagree with you, it usually shows in the first days to a couple of weeks — and a start date turns “I’ve been feeling off” into something a pharmacist can actually work with. Do not stop a prescribed medicine on your own.

Always talk with your pharmacist or doctor before making changes to your medications or supplements, particularly if you take several medications or have an ongoing health condition.

St. John's Wort safety at a glance

St. John's Wort overall Use caution Generally well tolerated short-term but has many serious drug interactions and can cause sun sensitivity.

Pregnancy Possibly Unsafe When used orally. Preliminary population research has found that taking St. John's wort while pregnant is associated with offspring that develop neural tube, ur... Read the full pregnancy detail

Breastfeeding Possibly Unsafe When used orally. Nursing infants of mothers who take St. John's wort have a greater chance of experiencing colic, drowsiness, and lethargy; avoid using. Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center) — the full detail is in the Special populations card below. Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Still wondering about combining Valacyclovir and St. John's Wort? Ask Dr. Brian Staiger, PharmD, BCPS directly ›

How we checked

Why No Interaction Is Listed for Valacyclovir

Interactions in our licensed database are recorded against drug classes, not just single drug names. Valacyclovir is filed under 3 classifications — organic anion transporter 1 (oat1) substrates, seizure threshold lowering drugs, oral drugs. St. John's Wort has documented interactions with 47 drug classes — the most serious being alprazolam (xanax) (major), contraceptive drugs (major) and cyclosporine (neoral, sandimmune) (major) — and none of Valacyclovir’s classifications are among them.

Classification data comes from our licensed Natural Medicines dataset. A medication can belong to classes beyond those recorded there, so this describes how the check was run — it is not a safety guarantee.

Keep it in perspective

St. John's Wort Does Interact With Other Medications

St. John's Wort has 755 major, 388 moderate known drug interactions in our database — Valacyclovir isn’t one of them. If you take anything else, check it against the full list below.

Major 755 Moderate 388 No known interaction 1,687 (incl. Valacyclovir)

Taking anything else?

Check Another of Your Medications Against St. John's Wort

Covers the 2,830 medications we’ve checked against St. John's Wort. Pick one to open its full report.

What to actually watch for

No Interaction Found — But Data Suggests St. John's Wort and Valacyclovir May Share Several of the Same Side Effects

This is not an interaction. Neither one changes how your body handles the other, and nothing here says they react together. What our sources do show is that each has separately been linked to the effects below — so taking both can make those effects more likely to turn up, and harder to pin on one or the other if they do. 8 of them are worth acting on rather than waiting out — marked below.

Mania or an unusually elevated mood / Confusion Worth acting on Additional detail
St. John's Wort
“St. John's wort can induce hypomania in depressed patients and mania in depressed patients with occult bipolar disorder. Cases of first-episode psychosis have been reported for females who used St. John's wort orally. In both cases, symptoms resolved following discontinuation of St. John's wort and treatment with antipsychotics for several weeks.”

St. John's Wort · Natural Medicines adverse-effect record, reported in anorexia.
6 sources cited

325. O'Breasail AM, Argouarch S. Hypomania and St John's wort. Can J Psychiatry 1998;43:746-7.

3524. Schneck C. St. John's wort and hypomania. J Clin Psychiatry 1998;59:689. PubMed

3555. Nierenberg AA, Burt T, Matthews J, et al. Mania associated with St. John's wort. Biol Psychiatry 1999;46:1707-8. PubMed

3568. Moses EL, Mallinger AG. St. John's wort: Three cases of possible mania induction. J Clin Psychopharmacol 2000;20:115-7. PubMed

10845. Hammerness P, Basch E, Ulbricht C, et al. St. John's wort: a systematic review of adverse effects and drug interactions for the consultation psychiatrist. Psychosomatics 2003;44:271-82. PubMed

76047. Barbenel, D. M., Yusufi, B., O'Shea, D., and Bench, C. J. Mania in a patient receiving testosterone replacement postorchidectomy taking St John's wort and sertraline. J Psychopharmacol 2000;14(1):84-86.
Valacyclovir

Listed in the ADVERSE REACTIONS section of the FDA label for Valacyclovir. Read the label on DailyMed ›
Hallucinations Worth acting on Additional detail

St. John's Wort

“Orally, St. John's wort is generally well tolerated.

Most Common Adverse Effects:

Orally: Diarrhea, dizziness, dry mouth, gastrointestinal discomfort (mild), fatigue, headache, insomnia, restlessness, and sedation.

Topically: Skin rash and photodermatitis.

Serious Adverse Effects (Rare):

Orally: There have been rare case reports of suicidal ideation and psychosis after taking St. John's wort.”

St. John's Wort · Natural Medicines adverse-effect record, reported in cluster headache.

Valacyclovir

Listed in the ADVERSE REACTIONS section of the FDA label for Valacyclovir. Read the label on DailyMed ›
Low mood Worth acting on Additional detail
St. John's Wort
“A case of syndrome of inappropriate secretion of antidiuretic hormone (SIADH) in a 67-year-old male with depression has been reported. During a 3-month period, the patient was taking St. John's wort 300 mg daily then increased to 600-900 mg daily with no adverse effects despite a low serum sodium level of 122mEq/L, elevated levels of urine sodium, and urine osmolality suggestive of SIADH. St.”

St. John's Wort · Natural Medicines adverse-effect record, reported in depression.
1 source cited

95508. Jones D. Tourian LT, Margolese H. Possible association of syndrome of Inappropriate secretion of antidiuretic hormone with St. John's wort use. J of Clin Psychopharmacol 2014:34(6):759-60. PubMed
Valacyclovir

Listed in the ADVERSE REACTIONS section of the FDA label for Valacyclovir. Read the label on DailyMed ›
Kidney problems Worth acting on Additional detail
St. John's Wort
“Orally, St. John's wort has been associated with a case report of acute kidney failure in a 46-year-old female after one dose of homemade St. John's wort tea. Three sessions of hemodialysis were required before there was full recovery. However, causality is unclear since the patient had also been taking diclofenac intermittently for a month prior to developing kidney failure.”

St. John's Wort · Natural Medicines adverse-effect record, reported in kidney failure.
1 source cited

106741. Adibelli Z, Karacay I, Demir M, Duran C. St. John's Wort (Hypericum perforatum)-related acute kidney injury. Blood Purif. 2021 Aug 24:1-3. doi: 10.1159/000518349.
Valacyclovir

Listed in the ADVERSE REACTIONS section of the FDA label for Valacyclovir. Read the label on DailyMed ›
Raised blood pressure Worth acting on Additional detail
St. John's Wort
“In clinical research, palpitations have been reported for patients taking St. John's wort orally, although the number of these events was higher for the patients taking sertraline. In one case report, an adult female developed recurrent palpitations and supraventricular tachycardia (SVT) within 3 weeks of initiating St. John's wort 300 mg daily.”

St. John's Wort · Natural Medicines adverse-effect record, reported in hypertension.
6 sources cited

76070. van Gurp, G., Meterissian, G. B., Haiek, L. N., McCusker, J., and Bellavance, F. St John's wort or sertraline? Randomized controlled trial in primary care. Can Fam Physician 2002;48:905-912.

106051. Fisher KA, Patel P, Abualula S, Concepion L. St. John's Wort-Induced Supraventricular Tachycardia. Cureus. 2021 Apr 7;13(4):e14356. PubMed

10843. Hypericum Depression Trial Study Group. Effect of Hypericum perforatum (St. John's wort) in major depressive disorder: a randomized controlled trial. JAMA 2002;287:1807-14. PubMed

8931. Irefin S, Sprung J. A possible cause of cardiovascular collapse during anesthesia: long-term use of St. John's Wort. J Clin Anesth 2000;12:498-9. PubMed

76073. Zullino, D. and Borgeat, F. Hypertension induced by St. John's Wort - a case report. Pharmacopsychiatry 2003;36(1):32. PubMed

76128. Cappuzzo, K. A. Herbal product use in a patient with polypharmacy. Consult Pharm. 2006;21(11):911-915. PubMed
Valacyclovir

Listed in the ADVERSE REACTIONS section of the FDA label for Valacyclovir. Read the label on DailyMed ›
Liver problems Worth acting on Additional detail
St. John's Wort
“A case of acute hepatitis with prolonged cholestasis and features of vanishing bile duct syndrome has been reported for a patient who used tibolone and St. John's wort orally for 10 weeks. A case of jaundice with transaminitis and hyperbilirubinemia has been reported for a 79 year-old female who used St. John's wort and copaiba. Laboratory values normalized 7 weeks after discontinuation of both products.”

St. John's Wort · Natural Medicines adverse-effect record, reported in cholestasis.
2 sources cited

76135. Etogo-Asse, F., Boemer, F., Sempoux, C., and Geubel, A. Acute hepatitis with prolonged cholestasis and disappearance of interlobular bile ducts following tibolone and Hypericum perforatum (St. John's wort). Case of drug interaction? Acta Gastroenterol.Be

95505. Agollo MC, Miszputen SJ, Diament J. Hypericum perforatum-induced hepatotoxicity with possible association with copaiba (copaifera langsdorffii desf): a case report. Einstein (Sao Paulo) 2014;12(3):355-7.
Valacyclovir

Listed in the ADVERSE REACTIONS section of the FDA label for Valacyclovir. Read the label on DailyMed ›
Bleeding or bruising Worth acting on Additional detail
St. John's Wort
“Orally, St. John's wort can cause intermenstrual or abnormal menstrual bleeding. However, this effect has occurred in patients who were also taking an oral contraceptive. Changes in menstrual bleeding might be the result of a drug interaction. Also, St. John's wort has been associated with anorgasmia and frequent urination when used orally.

Sexual dysfunction can occur with St.”

St. John's Wort · Natural Medicines adverse-effect record, reported in antidepressant-induced sexual dysfunction.
5 sources cited

1292. Yue QY, Bergquist C, Gerden B. Safety of St. John's wort (Hypericum perforatum). Lancet 2000;355:576-7. PubMed

76056. Ratz, A. E., von Moos, M., and Drewe, J. [St. John's wort: a pharmaceutical with potentially dangerous interactions]. Schweiz Rundsch.Med Prax. 5-10-2001;90(19):843-849.

10843. Hypericum Depression Trial Study Group. Effect of Hypericum perforatum (St. John's wort) in major depressive disorder: a randomized controlled trial. JAMA 2002;287:1807-14. PubMed

76070. van Gurp, G., Meterissian, G. B., Haiek, L. N., McCusker, J., and Bellavance, F. St John's wort or sertraline? Randomized controlled trial in primary care. Can Fam Physician 2002;48:905-912.

4836. Assalian P. Sildenafil for SJW-induced sexual dysfunction. J Sex Marital Ther 2000;26:357-8.
Valacyclovir

Listed in the ADVERSE REACTIONS section of the FDA label for Valacyclovir. Read the label on DailyMed ›
Sun sensitivity / Hair loss Additional detail
St. John's Wort
“Both topical and chronic oral use of St. John's wort can cause photodermatitis. The average threshold dose range for an increased risk of photosensitivity appears to be 1.8-4 grams St. John's wort extract or 5-10 mg hypericin, daily. Lower doses might not cause this effect. For example, a single dose of St.”

St. John's Wort · Natural Medicines adverse-effect record, reported in alopecia.
6 sources cited

206. Gulick RM, McAuliffe V, Holden-Wiltse J, et al. Phase I studies of hypericin, the active compound in St. John's Wort, as an antiretroviral agent in HIV-infected adults. AIDS Clinical Trials Group Protocols 150 and 258. Ann Intern Med 1999;130:510-4. PubMed

620. Golsch S, Vocks E, Rakoski J, et al. [Reversible increase in photosensitivity to UV-B caused by St. John's wort extract]. Hautarzt 1997;48:249-52.

758. Upton R, ed. St. John's wort, Hypericum perforatum: Quality control, analytical and therapeutic monograph. Santa Cruz, CA: American Herbal Pharmacopoeia 1997;1-32.

4628. Schempp CM, Ludtke R, Winghofer B, Simon JC. Effect of topical application of hypericum perforatum extract on skin sensitivity to solar simulated radiation. Photodermatol Photoimmunol Photomed 2000;16:125-8.

4631. Jacobson JM, Feinman L, Liebes L, et al. Pharmacokinetics, safety, and antiviral effects of hypericin, a derivative of St. John's Wort plant, in patients with chronic hepatitis C virus infection. Antimicrob Agents Chemother 2001;45:517-24. PubMed

6477. Lane-Brown MM. Photosensitivity associated with herbal preparations of St. John's wort (Hypericum perforatum). Med J Aust 2000;172:302.
Valacyclovir

Listed in the ADVERSE REACTIONS section of the FDA label for Valacyclovir. Read the label on DailyMed ›

Showing the 10 most notable of 21 shared effects — ranked by how unusual each one is, not just whether both lists mention it.

Reported for St. John's Wort but not commonly for Valacyclovir: stomach upset, low blood pressure, erection problems and dependence or withdrawal symptoms.

Effects for Valacyclovir come from the ADVERSE REACTIONS section of its FDA label; effects for St. John's Wort come from the Natural Medicines adverse-effect record, quoted above. Wording is matched across sources by our own clinical vocabulary, so treat this as a prompt to pay attention, not a diagnosis.

Special populations

St. John's Wort in Pregnancy & Breastfeeding

Pregnancy Possibly Unsafe

When used orally. Preliminary population research has found that taking St. John's wort while pregnant is associated with offspring that develop neural tube, urinary, and cardiovascular malformations. Subgroup analyses suggest that these risks may be higher when taking St. John's wort during the first trimester when compared with the second or third trimester. However, more research is needed to confirm these findings. Animal-model research also shows that constituents of St. John's wort might have teratogenic effects. Until more is known, St. John's wort should not be taken during pregnancy.

Lactation Possibly Unsafe

When used orally. Nursing infants of mothers who take St. John's wort have a greater chance of experiencing colic, drowsiness, and lethargy; avoid using.

DISCLAIMER: This tool is intended for informational purposes only, and should not be interpreted as specific medical advice. Patients should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.© 2026 Therapeutic Research Center

Overlapping uses

What Valacyclovir Is Prescribed For, and What St. John's Wort Has Been Studied For

These two come up together because they touch the same health topic — not because they do the same job. Valacyclovir is a prescription medicine with approved uses on its FDA label. St. John's Wort is a supplement: what follows is what researchers have looked at it for, and how strong that evidence is.

Valacyclovir is prescribed for: Valacyclovir tablets are used in adults to treat cold sores (herpes labialis), genital herpes (initial and recurrent episodes), and shingles (herpes zoster). They can also be taken daily as suppressive therapy to reduce how often genital herpes outbreaks occur, and to lower the risk of passing genital herpes to a partner. In children and adolescents, valacyclovir tablets are used to treat cold sores in those aged 12 and older, and chickenpox in those aged 2 to under 18. Valacyclovir has not been established as safe and effective for most uses in immunocompromised patients, with the exception of suppressive therapy for genital herpes in HIV-infected adults.

St. John's Wort has been studied for:

Genital herpes studied, not established St. John's Wort has been studied for this. Natural Medicines rates the evidence: Insufficient Reliable Evidence To Rate Read what the research shows

St. John's Wort for genital herpes

Topical St. John's wort has only been evaluated in combination with copper sulfate; its effect when used alone is unclear.

Effectiveness ratings and the research summaries above are the verbatim record from the Natural Medicines database, which grades evidence from “Effective” down to “Insufficient Reliable Evidence To Rate”. A rating below the top of that scale means researchers have looked at it — not that it works, and never that it can stand in for a prescribed medicine. Do not stop or replace Valacyclovir on your own; if you are taking St. John's Wort for the same health topic, tell your prescriber, especially if the medicine is being adjusted to a target.

From our Q&A

Questions About St. John's Wort or Valacyclovir

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers St. John's Wort or Valacyclovir, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Valacyclovir

This page covers St. John's Wort only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Valacyclovir page lists 27 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), African Wild Potato (moderate), Banderol (moderate), Biofeedback (moderate) and Caffeic Acid (moderate).

By severity: 1 major · 17 moderate · 9 minor.

From our pharmacist’s overview on the Valacyclovir page

“Valacyclovir (Valtrex) works against herpes outbreaks only if enough of it gets absorbed into your blood, and most of this list threatens exactly that. Of the 27 supplements on file, 17 can change how well oral medicines like this one are absorbed, and the single major-rated entry, activated charcoal, binds drugs in the gut outright.”

Reviewed by 2 · Jul 18, 2026

Open the Valacyclovir interaction page

One more smart check

Taking St. John's Wort as Part of a Dietary Supplement Product? Check It for Interactions

We hold 1,159 real supplement products containing St. John's Wort, each one broken down to its full ingredient list — and combination products often carry several ingredients besides St. John's Wort. Even though St. John's Wort itself has no known interaction with Valacyclovir, another ingredient on your label might. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where St. John's Wort and Valacyclovir Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement St. John's Wort

Top 25%

#158 of 1,452 supplements looked up here in the last 7 days

29 days ago today

Medication Valacyclovir

Top 5%

#31 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Where does our data come from?

Source: the Natural Medicines (TRC Healthcare) clinical database — the evidence-graded professional reference for herb & supplement interactions.
Citation library: 103,510 references behind our interaction content, 65,311 of them resolved to verified PubMed/DOI sources. See every St. John's Wort reference on this page ↓
Freshness: we automatically re-check this combination every week — this pair was last verified September 13, 2026. The St. John's Wort and Valacyclovir records this page draws on were last updated July 11, 2026.
What “no known interaction” means: no documented interaction in the sources above — not a guarantee of safety. Supplements are studied far less than prescription drugs, so we say exactly what the evidence supports, and nothing more.

Data structure & sourcing designed and verified by Dr. Brian Staiger, PharmD, BCPS.

Supplement

About St. John's Wort

What is St. John's Wort?

Mild to moderate depression
Anxiety and stress
Sleep problems
Menopausal symptoms
Wound healing (topical)

St. John's wort is a well-studied herb most often used for mild to moderate depression, and some research suggests it may help with this. However, it has many serious interactions with prescription medicines and is not safe for everyone, so always talk to your pharmacist or doctor before taking it.

Hypericum perforatum · Hypericaceae · Flowering tops and aerial parts (leaves and flowers) · Capsules, tablets, standardized extracts, teas, tinctures, and topical oils

An interaction check asks whether these two react with each other — it does not ask whether St. John's Wort is a good idea for someone in your situation. Here is what our St. John's Wort record says about it on its own.

St. John's Wort: dosing

There is no single official dose for St. John's wort. Products vary widely in strength, and many studies use extracts standardized to a set amount of hypericin or hyperforin. Because of this, the right dose depends on the specific product.The safest approach is to follow the directions on the product label and to choose a standardized extract from a reputable brand. Effects on mood, if any, may take several weeks to appear.

From our St. John's Wort monograph — the full record covers uses, side effects and every documented interaction.

Read the full St. John's Wort monograph & all interactions

Medication

About Valacyclovir

What Is Valacyclovir Used For?

Brand name: Valtrex

Valacyclovir tablets are used in adults to treat cold sores (herpes labialis), genital herpes (initial and recurrent episodes), and shingles (herpes zoster). They can also be taken daily as suppressive therapy to reduce how often genital herpes outbreaks occur, and to lower the risk of passing genital herpes to a partner.

In children and adolescents, valacyclovir tablets are used to treat cold sores in those aged 12 and older, and chickenpox in those aged 2 to under 18. Valacyclovir has not been established as safe and effective for most uses in immunocompromised patients, with the exception of suppressive therapy for genital herpes in HIV-infected adults.

Most-Reported Side Effects for Valacyclovir

From FAERS, the FDA’s public side-effect reporting system (70,056 reports, all brands). Reports are voluntary and are not proof the drug caused the effect.

Fatigue 4,317 reports

Nausea 3,985 reports

Diarrhea 3,648 reports

Headache 2,964 reports

Fever 2,753 reports

See full Valacyclovir drug information

Keep checking

Other Drugs & St. John's Wort

Browse every other medication we’ve checked against St. John's Wort — both the ones with a known interaction and the ones without. Select any drug for the full detail.

755Major

388Moderate

0Minor

1,686No known interaction

755 Major 388 Moderate 1,686 No interaction

Major

755 interactions

Showing 60 of 755 major interactions — see all 755 on the St. John's Wort page.

Moderate

388 interactions

Showing 60 of 388 moderate interactions — see all 388 on the St. John's Wort page.

No interaction 1,686 drugs checked — show the list

We also checked St. John's Wort against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 1,686 medications checked with no known interaction — see the full St. John's Wort list.

See the full St. John's Wort interactions page

See every supplement checked against Valacyclovir, ranked by severity

Evidence & sources

St. John's Wort References

The 152 references that drive our St. John's Wort monograph and interaction data, from the evidence-graded Natural Medicines (TRC Healthcare) database. Citations with a link open the study on PubMed or the publisher’s site.

Miller LG. Herbal Medicinals: Selected clinical considerations focusing on known or potential drug-herb interactions. Arch Intern Med 1998;158:2200-11.
Gulick RM, McAuliffe V, Holden-Wiltse J, et al. Phase I studies of hypericin, the active compound in St. John's Wort, as an antiretroviral agent in HIV-infected adults. AIDS Clinical Trials Group Protocols 150 and 258. Ann Intern Med 1999;130:510-4. PubMed
O'Breasail AM, Argouarch S. Hypomania and St John's wort. Can J Psychiatry 1998;43:746-7.
Johne A, Brockmoller J, Bauer S, et al. Pharmacokinetic interaction of digoxin with an herbal extract from St John's wort (Hypericum perforatum). Clin Pharmacol Ther 1999;66:338-45.
Gordon JB. SSRIs and St. John's Wort: possible toxicity? Am Fam Physician 1998;57:950, 953.
Golsch S, Vocks E, Rakoski J, et al. [Reversible increase in photosensitivity to UV-B caused by St. John's wort extract]. Hautarzt 1997;48:249-52.
Bove GM. Acute neuropathy after exposure to sun in a patient treated with St. John's Wort. Lancet 1998;352:1121-2. PubMed
Brockmoller J, Reum T, Bauer S, et al. Hypericin and pseudohypericin: pharmacokinetics and effects on photosensitivity in humans. Pharmacopsychiatry 1997;30:94-101. PubMed
Upton R, ed. St. John's wort, Hypericum perforatum: Quality control, analytical and therapeutic monograph. Santa Cruz, CA: American Herbal Pharmacopoeia 1997;1-32.
Muller WE, Singer A, Wonnemann M, et al. Hyperforin represents the neurotransmitter reuptake inhibiting constituent of hypericum extract. Pharmacopsychiatry 1998;31:16-21.
Abul-Ezz SR, Barone GW, Gurley BJ, et al. Effect of herbal supplements on cyclosporine blood levels and associated acute rejection. Am Soc of Nephrol Ann Mtg, Toronto, CAN 2000;Oct. 11-16:abstract A3754.
Piscitelli SC, Burstein AH, Chaitt D, et al. Indinavir concentrations and St John's wort. Lancet 2000;355:547-8. PubMed
Yue QY, Bergquist C, Gerden B. Safety of St. John's wort (Hypericum perforatum). Lancet 2000;355:576-7. PubMed
Ruschitzka F, Meier PJ, Turina M, et al. Acute heart transplant rejection due to Saint John's wort. Lancet 2000;355:548-9. PubMed
Roberts JE, Wang RH, Tan IP, et al. Hypericin (active ingredient in St. John's wort) photo-oxidation of lens proteins. Photochem Photobiol 1999;69:42S.
Gurley BJ, Barone GW. Herb-drug interaction involving St. John's wort and cyclosporine. AAPS Ann Mtg & Expo Indianapolis, IN:2000;Oct 29- Nov 2: presentation #3443.
Durr D, Stieger B, Kullak-Ublick GA, et al. St. John's Wort induces intestinal P-glycoprotein/MDR1 and intestinal and hepatic CYP3A4. Clin Pharmacol Ther 2000;68:598-604. PubMed
Lee A, Minhas R, Ito S, et al. Safety of St. John's wort during breastfeeding. Clin Pharmacol Ther 2000;67:130, abstract PII-64.
Schneck C. St. John's wort and hypomania. J Clin Psychiatry 1998;59:689. PubMed
Nierenberg AA, Burt T, Matthews J, et al. Mania associated with St. John's wort. Biol Psychiatry 1999;46:1707-8. PubMed
Nebel A, Schneider BJ, Baker RA, et al. Potential metabolic interaction between St. John's wort and theophylline. Ann Pharmacother 1999;33:502. PubMed
Moses EL, Mallinger AG. St. John's wort: Three cases of possible mania induction. J Clin Psychopharmacol 2000;20:115-7. PubMed
Beckman SE, Sommi RW, Switzer J. Consumer use of St. John's wort: A survey of effectiveness, safety, and tolerability. Pharmacotherapy 2000;20:568-74.
Peirce A. The American Pharmaceutical Association Practical Guide to Natural Medicines. New York, NY: William Morrow and Co., 1999.
Mai I, Kruger H, Budde K, et al. Hazardous pharmacokinetic interaction of Saint John's wort (Hypericum perforatum) with the immunosuppressant cyclosporin. Int J Clin Pharmacol Ther 2000;38:500-2. PubMed
Schempp CM, Muller K, Winghofer B, et al. Single-dose and steady-state administration of Hypericum perfotatum extract (St. John's wort) does not influence skin sensitivity to UV radiation, visible light, and solar-stimulated radiation. Arch Dermatol 2001;
Schempp CM, Ludtke R, Winghofer B, Simon JC. Effect of topical application of hypericum perforatum extract on skin sensitivity to solar simulated radiation. Photodermatol Photoimmunol Photomed 2000;16:125-8.
Jacobson JM, Feinman L, Liebes L, et al. Pharmacokinetics, safety, and antiviral effects of hypericin, a derivative of St. John's Wort plant, in patients with chronic hepatitis C virus infection. Antimicrob Agents Chemother 2001;45:517-24. PubMed
Moschella C, Jaber BL. Interaction between cyclosporine and Hypericum perforatum (St. John's wort) after organ transplantation. Amer J Kidney Dis 2001;38:1105-7. PubMed
Karliova M, Treichel U, Malago M, et al. Interaction of Hypericum perforatum (SJW) with cyclosporin A metabolism in a patient after liver transplantation. J Hepatol 2000;33:853-5.
Mandelbaum A, Pertzborn F, Martin-Facklam M, Wiesel M. Unexplained decrease of cyclosporin trough levels in a compliant renal transplant patient. Nephrol Dial Transplant 2000;15:1473-4. PubMed
Assalian P. Sildenafil for SJW-induced sexual dysfunction. J Sex Marital Ther 2000;26:357-8.
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Medication overviews come from MedlinePlus (NIH); supplement label data from the NIH Dietary Supplement Label Database. Content is written and reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

Pharmacist Counseling Corner

Taking St. John's Wort and Valacyclovir Together: Common Questions

Is it safe to take St. John's Wort with Valacyclovir?

We do not list a known interaction between St. John's Wort and Valacyclovir. That does not guarantee the combination is risk-free, so confirm with your pharmacist or doctor — especially if you take other medications or have a health condition.

Do St. John's Wort and Valacyclovir have any of the same side effects?

Yes — our sources link each of them separately to 10 of the same effects. That is not an interaction: neither changes how your body handles the other. It does mean that if one of those effects turns up, it can be harder to tell which one is behind it. They are listed on this page with the source behind each.

Are St. John's Wort and Valacyclovir used for the same thing?

They overlap in purpose, which usually means the real question is whether you need both rather than whether they are safe together. This page lists the shared uses and how strong the evidence is for St. John's Wort in each. That is a conversation for your prescriber, especially if Valacyclovir is being adjusted to a target.

How was the St. John's Wort and Valacyclovir combination checked?

Interactions in our licensed database are recorded against drug classes. Valacyclovir is filed under 3 classifications, and St. John's Wort has documented interactions with 47 drug classes — none of Valacyclovir's classifications are among them. A medication can belong to classes beyond those recorded in our dataset, so this describes how the check was run rather than guaranteeing safety.

Does St. John's Wort interact with any other medications?

Yes. St. John's Wort has 1,143 documented drug interactions in our database — Valacyclovir is simply not one of them. If you take anything else, it is worth checking each one; they are all listed on this page.

Does Valacyclovir interact with any supplements?

Yes. Valacyclovir has documented interactions with 27 supplements in our database — St. John's Wort is not one of them. The Valacyclovir interaction page linked on this page lists every one, ranked by severity.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

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St. John's Wort monograph Uses, safety profile, and every drug interaction in one place Valacyclovir drug information The full plain-English guide to this medication Valacyclovir supplement interactions Every supplement checked against Valacyclovir, ranked by severity Supplement interaction checker Check any supplement or product against your medications Browse medications A–Z Every drug we’ve checked against herbs & supplements References The 152 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Valacyclovir and St. John's Wort?

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.

case report: A written account of what happened to one patient, useful as a signal but not proof of cause.

anxiety: A feeling of worry, nervousness, or unease, sometimes along with a racing heart or restlessness.

cholestasis: A slowing of bile flow out of the liver; bile is the fluid that helps digest fat, and this backup can cause itching and yellow skin.

depression: A lasting low mood with loss of interest that affects everyday life.

diarrhea: Loose, watery bowel movements that happen more often than normal.

Drug Interactions: The label section listing other medicines, foods, or substances that can change how a medicine works or raise the chance of side effects.

hemodialysis: A treatment that uses a machine to filter waste and extra fluid from the blood when the kidneys cannot.

hepatitis: Inflammation of the liver, which can be caused by infections, alcohol, or certain medicines.

hyperbilirubinemia: A higher-than-normal level of bilirubin in the blood, which can cause yellowing of the skin or eyes.

hypomania: A milder form of mania, with raised energy and mood that is less severe and shorter-lasting than a full manic episode.

insomnia: Trouble falling asleep, staying asleep, or getting restful sleep.

jaundice: Yellowing of the skin and the whites of the eyes caused by too much bilirubin in the blood.

mania: A period of unusually high energy, racing thoughts, and an excited or irritable mood that is more extreme than normal.

palpitations: The feeling that your heart is racing, pounding, fluttering, or skipping beats.

photosensitivity: An unusually strong skin reaction, such as burning or rash, after being in sunlight or other ultraviolet light.

psychosis: A state of losing touch with reality, such as seeing or hearing things that are not there or holding false beliefs.

restlessness: An inability to stay calm or still, with a constant feeling of needing to move.

sedation: A calm, sleepy, slowed-down state caused by a medicine that relaxes the brain and body.

SIADH: Syndrome of inappropriate antidiuretic hormone: the body makes too much of a water-holding hormone, which lowers the level of sodium (salt) in the blood.

suicidal ideation: Thoughts about wanting to end your own life, which can range from a passing wish to a detailed plan.

tachycardia: A faster-than-normal heart rate, usually over 100 beats per minute.

topical: Applied onto the skin, eyes, or another body surface to work mainly where it is placed.