Supplements and Co-codamol.
Co-codamol, sold under the brand names Solpadol, Tylex, Kapake, Zapain, is a combination opioid analgesic.
Co-codamol is a combination opioid analgesic. In UK prescribing that mostly means codeine combined with paracetamol, or dihydrocodeine combined with paracetamol. The combination places a weak opioid alongside paracetamol, allowing lower doses of each component for additive analgesia. The supplement surface combines the opioid concerns with the paracetamol concerns. Opioid side. Additive CNS depression with alcohol, benzodiazepines, kava, valerian at higher doses, magnesium glycinate at high doses at bedtime; serotonergic concerns for combinations containing tramadol. Paracetamol side. Additive hepatotoxicity at chronic high doses, particularly alongside alcohol or supplements with hepatic load. Codeine is a CYP2D6 prodrug requiring conversion to morphine for analgesic effect. CYP2D6 inhibitors (some SSRIs, certain supplements at high doses) reduce that conversion and the analgesic effect. The CYP2D6 ultra metaboliser genotype carries the opposite concern, with excessive morphine production.
Below are the 1 documented pair we have explicitly assessed against Co-codamol in the Distil database: 1 red. The pairs cluster around 1 mechanism: Additive serotonergic activity. 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 13 September 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.
Additive serotonergic activity
Red Does 5-HTP interact with Co-codamol?
5-HTP is turned into serotonin in the body, and co-codamol contains codeine, an opioid whose UK product information warns of serotonin syndrome with serotonergic medicines, so taking the two together can cause serotonin syndrome (agitation, sweating, tremor, a racing heart, confusion). Do not take 5-HTP with co-codamol; if you already take both, tell your GP or pharmacist, and do not stop a prescribed painkiller on your own.
Evidence: Limited human data, from small studies or case reports.
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 we grade severity, choose what's in scope, and what we exclude.
Every call on this page is reasoned. We publish the full rubric for severity tiers, the medication inclusion logic, the evidence grades we accept, and what we deliberately leave out. About three thousand words. Worth reading once if you use this tool more than occasionally.
Read the full methodologyA 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.
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Something missing?
If a supplement or medication you take isn't in our autocomplete, tell us. We go through what people flag every week and add what's missing.