Supplements and Procyclidine hydrochloride.
Procyclidine hydrochloride, sold under the brand names Kemadrin, Arpicolin, is used in Parkinson disease to modulate dopaminergic signalling.
Procyclidine hydrochloride is used in Parkinson disease to modulate dopaminergic signalling. The class includes levodopa (combined with carbidopa or benserazide to prevent peripheral conversion), dopamine agonists (ropinirole, pramipexole, rotigotine), MAO-B inhibitors (covered separately), COMT inhibitors, and amantadine. UK prescribing is overseen by neurology specialists. The supplement surface includes two specific timing rules. First, the protein and levodopa absorption rule. Large protein loads compete with levodopa for the same gut amino acid transporter, and need a 30 to 45 minute separation. Second, the iron and levodopa chelation rule. Iron supplements bind levodopa in the gut, reducing absorption and requiring strict separation. Vitamin B6 at high doses historically opposed levodopa monotherapy, but with carbidopa or benserazide given alongside this is no longer an issue at standard supplement doses. 5-HTP and St John's Wort warrant care, given serotonergic and MAO concerns.
Below are the 1 documented pair we have explicitly assessed against Procyclidine hydrochloride in the Distil database: 1 amber. The pairs cluster around 1 mechanism: Cholinergic vs anticholinergic (opposing). 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 15 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.
Cholinergic vs anticholinergic (opposing)
Amber Does Huperzine A interact with ?
Huperzine A raises acetylcholine, while procyclidine is an anticholinergic that blocks it. The two pull in opposite directions, so each may reduce the other's effect. It is worth mentioning the huperzine A to your prescriber.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
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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