Atropa belladonna · PhytoNexus

01 Identity and provenance

Accepted binomial: Atropa belladonna
Common names: Belladonna
Family (APG IV): Solanaceae
Part used: Leaf, Root
Verification tier: Tier 2 · Verified Clinical columns reviewed and a source is on record.
Reviewer note (2026 audit): Reference not supplied - claim unverified against primary literature.

02 Constituent chemistry

Chemical class	Marker compound	Synthetic analogue in use
Tropane alkaloids	L-Hyoscyamine Leaf, Root	Homatropine

The analogue column is what makes the interaction reasoning tractable: where a constituent has a marketed structural counterpart, the counterpart's interaction profile is the starting hypothesis for the plant.

Looking up structures and physicochemical properties from PubChem…

03 Stated application

Reported activity: Antispasmodic
Marketed in: Atropine sulfate injection
Reported adverse effects: Dry mouth

04 Interaction matrix

Source column, verbatim: Antihistamines
Normalised onto 1 canonical drug class below.

Curated from the reviewed source

Drug class	Severity	Mechanism type	Provenance	Expected effect
Antihistamines Immunology	4Contraindicated	PD-additive	curated B	Drowsiness, impaired coordination, dry mouth, urinary hesitancy, confusio…	why ▾
Chemistry of this pair. Tropane alkaloids are competitive muscarinic antagonists with central penetration. Class mechanism. Sedating antihistamines add to botanical CNS depression, and their antimuscarinic component adds to tropane alkaloid burden. Expected Drowsiness, impaired coordination, dry mouth, urinary hesitancy, confusion in the elderly. Management Prefer non-sedating agents. Warn about driving during the first week of combined use. Onset rapid Evidence B - reviewed clinical column, source pending Matched on “antihistamines” Find evidence for this pair Map this mechanism

Predicted from constituent chemistry

These edges are not clinical findings. Each one is a rule inference: a constituent class in this plant is known to act on a target that the drug class also acts on. They are shown because a blank cell reads as “safe”, and for a Tier 1 entry a blank cell only means “not yet looked at”. Treat them as a literature-search agenda, not as a warning.

Drug class	Severity	Mechanism type	Provenance	Expected effect
Anticholinergics Autonomic	4Contraindicated	PD-additive	predicted D	Anticholinergic toxidrome: dry mouth, urinary retention, blurred vision, …	why ▾
Chemistry of this pair. Tropane alkaloids are competitive muscarinic antagonists with central penetration. Class mechanism. Tropane alkaloids (atropine, hyoscine, hyoscyamine) are competitive muscarinic antagonists; added to prescribed anticholinergics, antihistamines or tricyclics the burden summates. Expected Anticholinergic toxidrome: dry mouth, urinary retention, blurred vision, tachycardia, delirium, hyperthermia. Management Calculate total anticholinergic burden. Avoid in older adults, prostatism and narrow-angle glaucoma. Onset rapid Evidence D - in silico rule prediction only Find evidence for this pair Map this mechanism
Antipsychotics CNS	4Contraindicated	PD-additive + PK-CYP	predicted D	Extrapyramidal symptoms, QT prolongation, excess sedation, or loss of ant…	why ▾
Chemistry of this pair. Tropane alkaloids are competitive muscarinic antagonists with central penetration. Class mechanism. Additive dopaminergic blockade, QT prolongation and sedation, plus CYP1A2, 2D6 and 3A4 modulation of clozapine, risperidone and quetiapine exposure. Expected Extrapyramidal symptoms, QT prolongation, excess sedation, or loss of antipsychotic control with inducers. Management ECG if other QT-prolonging agents are present. Consider clozapine level monitoring where inducers are stopped or started. Onset rapid Evidence D - in silico rule prediction only Find evidence for this pair Map this mechanism
Narrow-therapeutic-index CYP3A4 substrates Pharmacokinetic	4Contraindicated	PK-CYP3A4	predicted D	Toxic accumulation or subtherapeutic failure of the co-prescribed drug, s…	why ▾
Chemistry of this pair. Alkaloidal bases have pH-dependent absorption and commonly interact with hepatic CYP isoenzymes and efflux transporters. Class mechanism. Furanocoumarins, bergamottin, piperine, glabridin and berberine inhibit CYP3A4; hyperforin, andrographolide and several diterpenes induce it through PXR. Because CYP3A4 handles roughly half of marketed drugs, the affected list is broad and the direction is product-specific. Expected Toxic accumulation or subtherapeutic failure of the co-prescribed drug, sometimes fatal for antiarrhythmics, immunosuppressants and oncology agents. Management Screen the full regimen for 3A4 substrates. Where the substrate has a narrow index, avoid rather than monitor. Onset unspecified Evidence D - in silico rule prediction only Find evidence for this pair Map this mechanism
Antacids, PPIs and H2 blockers Gastrointestinal	2Moderate	PK-absorption	predicted D	Reduced or erratic absorption of alkaloids; heartburn and reflux from pre…	why ▾
Chemistry of this pair. Alkaloidal bases have pH-dependent absorption and commonly interact with hepatic CYP isoenzymes and efflux transporters. Class mechanism. Gastric pH elevation alters the dissolution and ionisation of alkaloidal and enteric-coated botanical products; menthol- and peppermint-oil products lose their enteric protection at high pH and can be released prematurely. Expected Reduced or erratic absorption of alkaloids; heartburn and reflux from premature release of volatile-oil preparations. Management Separate administration by 2 hours. Avoid non-enteric peppermint oil in reflux disease. Onset unspecified Evidence D - in silico rule prediction only Find evidence for this pair Map this mechanism

05 Hazard register

The audit recorded no hazard beyond the interaction profile. The controlled-vocabulary field reads not assessed, which means the assessment has not been done rather than that it came back clear.

06 Confusable material

No same-genus or shared-common-name entry in the corpus.

07 Mechanism map

Chemistry sorts to the left, pharmacology to the right. Dashed edges are predicted. Drag nodes, scroll to zoom, export at 3× for a figure.

species

chemical class

marker compound

drug class

expected effect

hazard

08 Open literature

Abstract-scoped query built from this binomial, its common names and its marker compounds, run live against Europe PMC, PubMed and OpenAlex, then ranked locally against an evidence hierarchy.

Checking openFDA spontaneous reports…

09 Isomechanistic neighbours

Species whose interaction profile overlaps this one, ranked by shared severity weight rather than by count — a shared contraindication counts for more than a shared minor signal. Practical use: these are the plants you should not stack with this one, because the mechanisms summate.

Species	Family	Shared classes	Jaccard
Hyoscyamus niger Henbane	Solanaceae	5	1.00
Datura stramonium Datura	Solanaceae	5	1.00
Erythroxylum coca Coca	Erythroxylaceae	5	1.00
Duboisia myoporoides Corkwood	Solanaceae	5	0.83
Mucuna pruriens Mucuna	Fabaceae	3	0.43
Areca catechu Areca Nut	Arecaceae	3	0.50

10 References and notes

No citation is on record for this entry. That is itself the finding: the audit flagged it, and it is why the entry does not carry an A evidence grade.

Curator notes

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