Supplements and Theophylline.
Theophylline, sold under the brand names Slo-Phyllin, Uniphyllin, Theo-24, Elixophyllin, is a methylxanthine bronchodilator. The therapeutic window is narrow.
Theophylline is a methylxanthine bronchodilator. In current UK practice that mostly means theophylline (less commonly aminophylline). The therapeutic window is narrow. Plasma levels are monitored because both efficacy and toxicity (nausea, tremor, arrhythmia, seizure) sit close together. The supplement surface is large because theophylline is heavily CYP1A2 metabolised. Smoking induces CYP1A2 and drops plasma levels, pushing doses higher. On smoking cessation, levels rise and doses need adjustment. Caffeine is a methylxanthine itself and stacks additively at high intake. Several supplements influence CYP1A2. Cruciferous vegetables and concentrated extracts modestly induce. Certain quinolone pathway compounds inhibit. The class is much less prescribed today than thirty years ago, since inhaled beta-2 agonists and inhaled corticosteroids dominate asthma and COPD treatment. But theophylline remains in some specialist prescribing.
Below are the 2 documented pairs we have explicitly assessed against Theophylline in the Distil database: 2 caution. The pairs cluster around 2 mechanisms: CYP induction and CYP1A2 induction. Every call is cited to either a clinical reference (PMID) or the British National Formulary. Anything not on this list is either still to be assessed or beyond our database scope. The checker beneath surfaces assessments by supplement, and the missing-item form at the bottom of the page routes any uncatalogued supplement into our next curation pass.
Documented interactions
Last reviewed 21 June 2026. Each interaction below lists the evidence its assessment drew on: some rest on studies of the exact pair, others on mechanism evidence, where a citation may support one part of the reasoning rather than the exact combination. The evidence line on each entry says which.
CYP induction
Caution Does St John's Wort interact with Theophylline?
Theophylline has a narrow safe range, so do not start or stop St John's Wort while taking it without telling whoever prescribes it, as your dose and blood levels may need checking. The evidence here pulls both ways: one published case describes someone needing markedly more theophylline while taking St John's Wort, while the one controlled study in healthy volunteers found no change in theophylline levels at all.
Evidence: Limited human data, from small studies or case reports.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
CYP1A2 induction
Caution Does Resveratrol interact with Theophylline?
Resveratrol may speed up how the body clears theophylline, which could lower theophylline levels and reduce how well it controls your breathing. Theophylline has a narrow safe range, so tell your respiratory team before taking resveratrol rather than starting it on your own.
Evidence: No direct study of this exact combination yet; the caution rests on a plausible mechanism or on reports involving a related medicine.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
What this list does not say. Pairs not flagged here are not implicitly safe. They are either not yet in our database, or fall outside our inclusion scope (food-supplement interactions only; for drug-drug interactions, the BNF is authoritative). Use the checker below to surface any supplement, and submit a missing item if you take something we have not catalogued.
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How the checker decides
Every result has a source
Each pair we have assessed is cited to a published study (PMID) or the British National Formulary, so you can read the source yourself.
Four kinds of answer
Severe, caution, no known interaction, and not yet assessed. A pair we have not assessed is never shown as clear.
- Severe
- Caution
- No known interaction
- Not yet assessed
Nothing in our data is not a clearance
When nothing in our data records a problem with a pair, the result says no known interaction at typical doses, which is not a clearance: your pharmacist or GP can check the pair against your full medical history.
A full supplement review, built around you, not a generic stack.
The free checker answers one interaction question at a time. A Distil report reviews the bigger picture: your goals, diet, medications, current supplements and any blood results you provide, then shows what appears worth keeping, changing, adding or leaving out.
- what your diet already covers, so you are not adding a capsule for something food is already handling
- which evidence-graded compounds are worth considering for your goals, and which were considered but left out
- what to keep, change or stop from what you already take, plus the order to introduce anything new
- how your medications and complete supplement stack fit together, with daily timing and a clear point for reassessment
The interaction check is one section of the full report. You also get the reasoning behind each recommendation and the evidence references used.
£49 until 30 June 2027 · £79 from 1 July 2027.
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