Dimenhydrinate (Dramamine)

2-benzhydryloxy-N,N-dimethylethanamine;8-chloro-1,3-dimethyl-7H-purine-2,6-dione

Overview

Dimenhydrinate (Dramamine) belongs to Deliriants.

Key safety note: At high exposure can cause anticholinergic delirium and cardiotoxicity (sodium/potassium-channel block → QRS/QT prolongation and arrhythmias).
Effects
Subjective effects vary. What a substance feels like depends on dose, individual physiology, mindset, and setting. The points below describe commonly reported effects, not guaranteed, uniform, or desirable outcomes.
    Dosing & duration
    Harm-reduction note: These are commonly cited reference ranges, not a recommendation or a “safe” dose. Potency, purity, body chemistry, tolerance, and drug combinations vary widely. Start low, go slow, wait for full effects before redosing, and never assume an unknown product matches these figures. Missing data is not evidence of safety.

    Not reported

    Dose ranges

    Duration

    Chemical & Physical Properties
    FormulaC24H28ClN5O3
    Molar mass469.96 g/mol
    StateSolid
    Melting point102–107 °C
    Boiling pointNot reported
    DensityNot reported
    Vapor pressureNot reported
    pKaNot reported
    LogPNot reported
    SolubilitySlightly soluble (1–10 mg/mL at 22 °C) (NTP, 1992), 3000 mg/L, Freely soluble in alcohol and chloroform. Soluble in benzene. Water solubility about 3 mg/mL. Almost insoluble in ether
    Refractive indexNot reported
    Identifiers & Synonyms
    CASNot reported
    CAS (enantiomer)
    PubChem CID10660
    InChIKeyNFLLKCVHYJRNRH-UHFFFAOYSA-N
    InChIInChI=1S/C17H21NO.C7H7ClN4O2/c1-18(2)13-14-19-17(15-9-5-3-6-10-15)16-11-7-4-8-12-16;1-11-4-3(9-6(8)10-4)5(13)12(2)7(11)14/h3-12,17H,13-14H2,1-2H3;1-2H3,(H,9,10)
    SMILESCN1C2=C(C(=O)N(C1=O)C)NC(=N2)Cl.CN(C)CCOC(C1=CC=CC=C1)C2=CC=CC=C2

    Synonyms

    • Dramamine
    • Vomex
    Pharmacodynamics & Biochemistry

    Dimenhydrinate is not a single molecule but a 1:1 salt of two components: diphenhydramine (a first-generation antihistamine) and 8-chlorotheophylline (a xanthine related to caffeine). Diphenhydramine is the pharmacologically dominant part. The 8-chlorotheophylline is added mainly to offset its drowsiness by contributing a mild stimulant effect. Diphenhydramine is a lipophilic ethanolamine H1-antihistamine that acts as an inverse agonist / competitive antagonist at histamine H1 receptors. Because it readily crosses the blood–brain barrier, central H1 blockade produces the sedation and much of the antiemetic and anti-vertigo action for which dimenhydrinate is used: chiefly by damping signalling from the vestibular system and the vomiting centre. It also has marked antimuscarinic (anticholinergic) activity, blocking muscarinic acetylcholine receptors. This adds to the anti-motion-sickness effect but also causes the typical anticholinergic side-effects, dry mouth, blurred vision, urinary retention and constipation, and, in overdose, an anticholinergic delirium (agitation, hallucinations, mydriasis, flushing, hyperthermia, tachycardia) that underlies its recreational 'deliriant' misuse. At toxic concentrations diphenhydramine also blocks cardiac sodium and potassium channels, which can cause QRS widening, QT prolongation and arrhythmias, while the 8-chlorotheophylline component adds a stimulant load. Elimination is hepatic.

    Biological targets

    • H1
    • mAChR
    Pharmacokinetics
    BioavailabilityNot reported
    TmaxNot reported
    Half-lifeSeveral hours
    VdNot reported
    Protein bindingNot reported
    MetabolismHepatic
    ExcretionNot reported
    Toxicology & Safety
    Harm-reduction note: Toxicity and risk depend on dose, route, purity, combinations, setting, and individual health factors. Missing harms should never be interpreted as evidence of safety.

    Not reported

    At high exposure can cause anticholinergic delirium and cardiotoxicity (sodium/potassium-channel block → QRS/QT prolongation and arrhythmias). Additive sedation with alcohol and other CNS depressants. Anticholinergic burden is dangerous in the elderly and in children. Recreational high-dose use for its deliriant effect is associated with severe, unpleasant toxicity and hospitalisation.

    Legal Status
    Legal note: Legal status can change over time and may vary by country, region, formulation, analogue status, prescription context, and enforcement practice. Always confirm with current official sources before relying on this section.
    Interactions & Contraindications

    Drug interactions

    Alcohol, Anticholinergic drugs Additive sedation and anticholinergic load with alcohol, other antihistamines, tricyclics, antipsychotics and antispasmodics.
    Opioids, Benzodiazepines Enhanced CNS and respiratory depression with opioids, benzodiazepines and other sedatives.
    MAOIs MAO inhibitors can intensify its anticholinergic effects.

    Contraindications

    Known hypersensitivity to the drug hypersensitivity to diphenhydramine or other ethanolamine antihistamines.
    Closed-angle glaucoma narrow-angle glaucoma.
    Pre-existing bladder or urinary-tract disease, or drug-induced cystitis prostatic hypertrophy or bladder-neck obstruction with urinary retention.
    Respiratory disease or sleep apnoea acute asthma attack.
    Children (age-restricted; respiratory-depression risk) neonates and premature infants, with caution in young children (paradoxical excitation and toxicity).
    Usage & Context
    • Therapeutic.
    Sources & Evidence

    Further Information