Drug & supplement interaction

Caffeine + Methoxsalen

Methoxsalen brand names: Oxsoralen, Oxsoralen Ultra.

Minor Interaction
Medically reviewed by · Updated October 2026
The bottom line Minor

Methoxsalen falls into 2 drug categories that Caffeine can interact with; the most serious is rated minor. Theoretically, concomitant use might increase the levels and adverse effects of caffeine.

Read the full interaction report
SeverityMinor
LikelihoodPossible
Interactions2
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Caffeine and Methoxsalen

These two interact in 2 distinct ways. Each one is explained separately below.

Why Are There 2 Interactions?

Caffeine interacts with whole categories of medication. Methoxsalen falls into 2 of those categories, so it can interact with Caffeine in 2 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Minor).

Minor

CYTOCHROME P450 1A2 (CYP1A2) INHIBITORS

1 of 2

Why this applies to Methoxsalen

Methoxsalen falls under CYTOCHROME P450 1A2 (CYP1A2) INHIBITORS — the group Caffeine interacts with.

Theoretically, concomitant use might increase the levels and adverse effects of caffeine.
Caffeine is metabolized by CYP1A2. Theoretically, drugs that inhibit CYP1A2 may decrease the rate of caffeine clearance and increase caffeine levels.
Severity Minor Likelihood Possible Evidence D

Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's a small thing worth knowing if you take methoxsalen (Oxsoralen) and enjoy your coffee or tea. Methoxsalen can block a liver enzyme called CYP1A2, and that same enzyme is the one your body uses to clear out caffeine. When the enzyme is slowed down, caffeine can hang around a bit longer than usual. So your usual two cups might hit a little harder, leaving you feeling jittery, wired, restless, or having trouble falling asleep, with a faster or pounding heartbeat.

The good news: this is rated minor and is mostly theoretical, based on lab studies rather than real patient reports. Most people won't notice much. If you do feel extra buzzed, just ease back on caffeine and mention it to your pharmacist or doctor.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Hagg S, Spigset O, Mjorndal T, Dahlqvist R. Effect of caffeine on clozapine pharmacokinetics in healthy volunteers. Br J Clin Pharmacol 2000;49:59-63. PubMed
  2. Carrillo JA, Benitez J. Clinically significant pharmacokinetic interactions between dietary caffeine and medications. Clin Pharmacokinet 2000;39:127-53. PubMed
Minor

METHOXSALEN (Oxsoralen)

2 of 2
Theoretically, methoxsalen might increase the levels and adverse effects of caffeine.
Methoxsalen reduces caffeine metabolism.
Severity Minor Likelihood Possible Evidence B

Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the simple version of what's going on with methoxsalen and caffeine. Your body uses a liver enzyme (CYP1A2) to clear caffeine. Methoxsalen slows that enzyme down, so caffeine tends to hang around longer than usual. In other words, the methoxsalen isn't changed here, the caffeine is what builds up.

What that can feel like is too much coffee even from your normal amount: a racing or pounding heart, jitters, trouble sleeping, or feeling anxious. The good news is this is rated minor and the evidence is on the weaker side, so for most people it's a mild effect. Still, if you notice extra jitteriness while taking methoxsalen, easing back on coffee or tea is reasonable. Check with your pharmacist or doctor before changing anything.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Mays, D. C., Camisa, C., Cheney, P., Pacula, C. M., Nawoot, S., and Gerber, N. Methoxsalen is a potent inhibitor of the metabolism of caffeine in humans. Clin.Pharmacol.Ther. 1987;42(6):621-626. PubMed

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Caffeine Also Interacts With Other Medications

Caffeine has 8 major, 483 moderate, 163 minor known drug interactions in our database — the Methoxsalen one above is among them. If you take anything else, check it against the full list below.

Major 8 Moderate 483 Minor 163 No known interaction 2,176 (incl. Methoxsalen)
Taking anything else?

Check Another of Your Medications Against Caffeine

Covers the 2,830 medications we’ve checked against Caffeine. Pick one to open its full report.

From our Q&A

Questions About Caffeine or Methoxsalen

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Caffeine or Methoxsalen, 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 Methoxsalen

This page covers Caffeine only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Methoxsalen page lists 48 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Alfalfa (moderate), Angelica Archangelica (moderate), Arrach (moderate) and Bergamot (moderate).

By severity: 1 major · 33 moderate · 14 minor.

From our pharmacist’s overview on the Methoxsalen page

“Methoxsalen (Oxsoralen) works by deliberately making skin sensitive to ultraviolet light to treat psoriasis and vitiligo, so its supplement list deserves an unhurried, serious read. Twenty of the 48 ingredients on file add photosensitizing effects of their own, bergamot oil among them, and that stacking can push a carefully dosed light…”

Reviewed by 2 · Jul 18, 2026

Open the Methoxsalen interaction page

One more smart check

Taking Caffeine as Part of a Dietary Supplement Product? Check It for Interactions

We hold 6,775 real supplement products containing Caffeine, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Caffeine. Your product may carry other ingredients that interact with Methoxsalen too, on top of Caffeine — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Caffeine and Methoxsalen 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 Caffeine
Top 5%

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

29 days ago today
Medication Methoxsalen
Steady interest

#2,786 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.

Supplement

About Caffeine

What is Caffeine?

  • Mental alertness and reducing fatigue
  • Improving athletic performance
  • Headache and migraine relief
  • Boosting focus and concentration
  • Weight loss aid

Caffeine is a natural stimulant found in coffee, tea, and many other plants and products. In moderate amounts it can boost alertness and reduce tiredness for most healthy adults, but too much can cause jitteriness, a racing heart, and sleep problems. Pregnant women and people with heart conditions or anxiety should be especially careful and check with a doctor or pharmacist.

Read the full Caffeine monograph & all interactions
Keep checking

Other Drugs & Caffeine

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

8Major
483Moderate
163Minor
2,175No known interaction
8 Major 483 Moderate 163 Minor 2,175 No interaction
Major

8 interactions

Moderate

483 interactions

Showing 60 of 483 moderate interactions — see all 483 on the Caffeine page.

Minor

163 interactions

Showing 60 of 163 minor interactions — see all 163 on the Caffeine page.

No interaction 2,175 drugs checked — show the list

We also checked Caffeine against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,175 medications checked with no known interaction — see the full Caffeine list.

See the full Caffeine interactions page
See every supplement checked against Methoxsalen, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Keep exploring
Caffeine monograph › Uses, safety, and every drug interaction in one place Methoxsalen supplement interactions › Every supplement checked against Methoxsalen, 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 Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Caffeine and Methoxsalen Together: Common Questions

Can you take Caffeine with Methoxsalen?
There is only a minor interaction, which is usually not serious. Read the full details on this page and confirm with your pharmacist before combining them.
Why are there 2 interactions listed for Caffeine and Methoxsalen?
Methoxsalen belongs to more than one drug category, and Caffeine interacts with each of those categories a little differently. We list every one so nothing is missed — your overall risk is driven by the most serious of them.
How serious is the Caffeine and Methoxsalen interaction?
We rate it Minor. This interaction is generally not clinically significant, but it remains worth noting and discussing with your pharmacist.

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

Still Have a Question About Methoxsalen and Caffeine?

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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.