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    Dimenhydrinate molecular structure

    Dimenhydrinate Stats & Data

    Depressant Deliriant
    Dime Drama Drams Gravol Dimate dramamine
    Chemical Class medicine
    Psychoactive Class Depressant
    Half-Life 5–8 hours (plasma elimination); individual variability expected.

    Pharmacology

    DrugBank
    State Solid

    Description

    Dimehydrinate was first described in the literature in 1949, and patented in 1950. Early research into dimenhydrinate focused on its role as an antihistamine for urticaria; the treatment of motion sickness was an accidental discovery. Dimenhydrinate, also known as B-dimethylaminoethyl benzohydrol ether 8-chlorotheophyllinate, is indicated to prevent nausea, vomiting, and dizziness caused by motion sickness. Dimenhydrinate is a combination of Diphenhydramine and 8-chlorotheophylline in a salt form, with 53%-55.5% dried diphenhydramine, and 44%-47% died 8-chlorotheophylline. The antiemetic properties of dimenhydrinate are primarily thought to be produced by diphenhydramine's antagonism of H1 histamine receptors in the vestibular system while the excitatory effects are thought to be produced by 8-chlorotheophylline's adenosine receptor blockade. When used in large doses, dimenhydrinate has been shown to cause a "high" characterized by hallucinations, excitement, incoordination, and disorientation. Dimenhydrinate was granted FDA approval on 31 May 1972.

    Mechanism of Action

    Dimenhydrinate is a theoclate salt that separates into diphenhydramine and 8-chlorotheophylline. While the exact mechanism of action is unknown, diphenhydramine is theorized to reduce disturbances to equilibrium through antimuscarinic effects or histamine H1 antagonism. 8-chlorotheophylline may produce excitation through blocking adenosine receptors, reducing the drowsiness produced by diphenhydramine.

    Pharmacodynamics

    Dimenhydrinate is indicated for the prevention and treatment of nausea, vomiting, or vertigo of motion sickness. It has a short duration of action of 4-8 hours. Patients should be counselled regarding pronounced drowsiness, avoiding alcohol and other sedatives, and exercising caution when operating a motor vehicle or heavy machinery.

    Metabolism

    Dimenhydrinate is a theoclate salt that separates into diphenhydramine and 8-chlorotheophylline. diphenhydramine can either be N-glucuronidated by UGTs to diphenhydramine N-glucuronide or N-demethylated by CYP2D6, CYP1A2, CYP2C9, and CYP2C19 to N-desmethyldiphenhydramine. N-desmethyldiphenhydramine can be N-demethylated again by the same enzymes to N,N-didesmethyldiphenhydramine, which undergoes oxidative deamination to form diphenylmethoxyacetic acid.

    Absorption

    A 50 mg oral film coated tablet reaches a Cmax of 72.6 ng/mL with a Tmax of 2.7 hours. A 100 mg suppository reaches a Cmax of 112.2 ng/mL with a Tmax of 5.3 hours.

    Toxicity

    Infants and children experiencing an overdose may lead to hallucinations, convulsions, or death. Adults experiencing an overdose may present with drowsiness, convulsions, coma, or respiratory depression. Treat overdoses with symptomatic and supportive measures including mechanically assisted ventilation. In mice the oral LD50 is 203 mg/kg, while in rats it is 1320 mg/kg. The intraperitoneal LD50 in mice is 149 mg/kg.

    Indication

    Dimenhydrinate is indicated for the prevention and treatment of nausea, vomiting, or vertigo of motion sickness.

    Half-life

    The plasma elimination half life of dimenhydrinate is 5-8 hours.

    Protein Binding

    Dimenhydrinate is 70-85% protein bound in plasma.

    Elimination

    Dimenhydrinate is predominantly eliminated in the urine. 1-3% of the dissociated diphenhydramine is eliminated in the urine unchanged, while 64% of diphenhydramine is eliminated in the urine as metabolites. The elimination of dimenhydrinate has not been fully studied.

    Volume of Distribution

    The volume of distribution of dimenhydrinate is 3-4 L/kg.

    Receptor Profile

    Receptor Actions

    Antagonists
    H1 histamine receptor antagonist (inverse agonist)
    Muscarinic acetylcholine receptor antagonist

    Receptor Binding

    Histamine H1 receptor antagonist

    History & Culture

    1947–1950

    Dimenhydrinate, originally designated Compound 1694, was developed through serendipitous observation rather than targeted research. In 1947, allergists Dr. Leslie Gay and Dr. Paul Carliner at Johns Hopkins Hospital were testing the compound as a potential treatment for hay fever and hives. Among their test subjects was a pregnant woman who had experienced motion sickness throughout her entire life. She discovered that taking dimenhydrinate shortly before boarding a trolley completely prevented her symptoms, while a placebo proved ineffective. These unexpected findings prompted pharmaceutical company G.D. Searle & Co. to conduct formal clinical trials the following year. The company administered dimenhydrinate or placebo to American troops during a ten-day transatlantic voyage aboard the General Ballou, a converted freight ship navigating rough seas. The results were positive, as was a subsequent trial conducted predominantly with women on the ship's return voyage. Gay and Carliner formally announced their discovery at a meeting of the Johns Hopkins Medical Society on February 14, 1949. G.D. Searle introduced the drug to the market under the brand name Dramamine later that year. The compound was first described in scientific literature in 1949 and received patent protection in 1950.

    Beyond its medical applications, dimenhydrinate has gained recognition for its recreational use as a deliriant substance. Users have developed various slang terms for this practice, including "drama," "dime," "dime tabs," "D-Q," "substance D," "d-house," and "drams." The act of using the drug recreationally is sometimes called "dramatizing" or "going a dime a dozen," the latter being a reference to the number of tablets typically required to achieve deliriant effects. The substance has also appeared in popular music. Modest Mouse released a song titled "Dramamine" on their 1996 debut album "This Is a Long Drive for Someone with Nothing to Think About," employing the drug's side effects as a metaphor for a deteriorating personal relationship. Car Seat Headrest later featured "The Ending of Dramamine" as the opening track on their album "How to Leave Town."

    Tolerance & Pharmacokinetics

    drugs.wiki
    Half-Life
    5–8 hours (plasma elimination); individual variability expected.
    Addiction Potential
    Low for therapeutic use; some cases of repetitive high‑dose misuse with psychological dependence reported.

    Tolerance Decay

    Full tolerance 3d Half tolerance 7d Baseline ~14d

    Anecdotal reports suggest rapid tolerance to deliriant/anticholinergic cognitive and hallucinatory effects with repeated dosing over days, with partial reversal over 1–2 weeks. Data quality low; avoid frequent use to reduce cumulative anticholinergic burden.

    Cross-Tolerances

    Diphenhydramine
    60% ●○○
    Doxylamine
    40% ●○○
    Cyclizine/Meclizine
    30% ●○○
    Promethazine
    30% ●○○

    Experience Report Analysis

    Erowid
    221 Reports
    1994–2020 Date Range
    18 With Age Data
    29 Effects Detected

    Demographics

    Gender Distribution

    Age Distribution

    Reports Over Time

    Effect Analysis

    Erowid

    Effects aggregated from 221 experience reports (221 Erowid)

    221 Reports
    29 Effects Detected
    11 Positive
    11 Adverse
    7 Neutral

    Effect Sentiment Distribution

    Confidence Distribution

    Positive Effects 11

    Anxiety Suppression 51.1% 70%
    Sedation 43.4% 70%
    Stimulation 29.9% 70%
    Music Enhancement 25.3% 70%
    Color Enhancement 25.3% 70%
    Tactile Enhancement 24.4% 70%
    Euphoria 15.8% 70%
    Focus Enhancement 15.8% 70%
    Empathy 12.2% 70%
    Body High 8.6% 70%
    Introspection 5.4% 70%

    Adverse Effects 11

    Confusion 33.9% 70%
    Memory Suppression 26.7% 70%
    Nausea 20.8% 70%
    Pupil Dilation 13.1% 70%
    Motor Impairment 12.7% 70%
    Headache 6.8% 70%
    Increased Heart Rate 5.4% 70%
    Sweating 5.0% 70%
    Psychosis 4.5% 70%
    Seizure 4.1% 70%
    Jaw Clenching 2.7% 70%

    Dose-Response Correlation

    How effect frequency changes across dose levels

    View data table
    Effect Common (n=14) Strong (n=28) Heavy (n=85)
    Visual Distortions 50.0% 71.4% 47.1%
    Anxiety Suppression 57.1% 46.4% 57.6%
    Sedation 50.0% 50.0% 41.2%
    Auditory Effects 42.9% 35.7% 47.1%
    Open-Eye Visuals 42.9% 32.1% 38.8%
    Color Enhancement 42.9% 25.0% 28.2%
    Stimulation 42.9% 32.1% 28.2%
    Memory Suppression 21.4% 42.9% 29.4%
    Confusion 35.7% 35.7% 36.5%
    Music Enhancement 28.6% 25.0% 30.6%
    Motor Impairment 28.6% 14.3% 15.3%
    Euphoria 28.6% 17.9% 15.3%
    Tactile Enhancement 21.4% 25.0% 23.5%
    Hospital 21.4% 21.4% 21.2%
    Nausea 21.4% 21.4% 21.2%

    Subjective Effect Ontology

    Experience Reports

    Structured effect tags extracted from 221 experience reports using a controlled vocabulary of 220+ canonical effects across 15 domains.

    Emotional

    anxiety suppression 113 51.1%

    Visual

    visual distortions 105 47.5%

    2 unique effects extracted · Derived from experience reports

    Dose–Effect Mapping

    Experience Reports

    How reported effects shift across dose tiers, based on 221 experience reports.

    Oral dose range: 450.0–900.0 mg (median 600.0 mg)
    Effect Common (n=14) Strong (n=28) Heavy (n=85)
    visual distortions
    50%
    71%
    47%
    		→
    anxiety suppression
    57%
    46%
    58%
    		→
    sedation
    50%
    50%
    41%
    		↓
    auditory effects
    43%
    36%
    47%
    		→
    open-eye visuals
    43%
    32%
    39%
    		→
    color enhancement
    43%
    25%
    28%
    		↓
    stimulation
    43%
    32%
    28%
    		↓
    memory suppression
    21%
    43%
    29%
    		↑
    confusion
    36%
    36%
    36%
    		→
    music enhancement
    29%
    25%
    31%
    		→
    motor impairment
    29%
    14%
    15%
    		↓
    euphoria
    29%
    18%
    15%
    		↓
    tactile enhancement
    21%
    25%
    24%
    		→
    hospital
    21%
    21%
    21%
    		→
    nausea
    21%
    21%
    21%
    		→
    pupil dilation
    21%
    7%
    14%
    		↓
    focus enhancement
    21%
    21%
    21%
    		→
    closed-eye visuals
    14%
    14%
    19%
    		↑
    body high
    14%
    14%
    8%
    		↓
    empathy
    14%
    14%
    8%
    		↓

    Showing top 20 of 30 effects

    Risk Escalation

    Sentiment Analysis

    Average frequency of positive vs adverse effects across dose tiers

    Common n=14
    8 positive 26.8% 6 adverse 30.9%
    Strong n=28
    9 positive 20.2% 9 adverse 21.4%
    Heavy n=85
    9 positive 18.8% 12 adverse 16.9%
    View effect breakdown

    Adverse Effects

    Effect Common (n=14) Strong (n=28) Heavy (n=85) Change
    Anxiety Suppression
    57%
    46%
    58%
    		0%
    Memory Suppression
    21%
    43%
    29%
    		+37%
    Confusion
    36%
    36%
    36%
    		2%
    Motor Impairment
    29%
    14%
    15%
    		-46%
    Nausea
    21%
    21%
    21%
    		0%
    Pupil Dilation
    21%
    7%
    14%
    		-34%
    Jaw Clenching —
    11%
    		— 0%
    Headache —
    7%
    8%
    		+15%
    Seizure —
    7%
    4%
    		-50%
    Psychosis — —
    6%
    		0%
    Sweating — —
    5%
    		0%
    Increased Heart Rate — —
    4%
    		0%
    Muscle Tension — —
    2%
    		0%

    Positive Effects

    Effect Common (n=14) Strong (n=28) Heavy (n=85) Change
    Color Enhancement
    43%
    25%
    28%
    		-34%
    Stimulation
    43%
    32%
    28%
    		-34%
    Music Enhancement
    29%
    25%
    31%
    		6%
    Euphoria
    29%
    18%
    15%
    		-46%
    Tactile Enhancement
    21%
    25%
    24%
    		9%
    Focus Enhancement
    21%
    21%
    21%
    		0%
    Body High
    14%
    14%
    8%
    		-42%
    Empathy
    14%
    14%
    8%
    		-42%
    Introspection —
    7%
    6%
    		-16%

    Dosage Distribution

    Dose distribution from experience reports

    Median: 600.0 mg IQR: 450.0–900.0 mg n=140

    Real-World Dose Distribution

    62K Doses

    From 350 individual dose entries

    Oral (n=263)

    Median: 500.0mg 25th: 150.0mg 75th: 600.0mg 90th: 1000.0mg
    mg/kg median: 6.647 mg/kg 75th: 10.059

    Common Combinations

    Most co-occurring substances in experience reports

    Form / Preparation

    Most common forms and preparations reported

    Body-Weight Dosing

    Dose relative to body weight from reports with weight data

    Median: 8.824 mg/kg IQR: 6.173–13.921 mg/kg n=136

    Redose Patterns

    Redosing behavior across 192 reports

    15.6% Redosed
    1.3 Avg Doses
    20m Median Interval
    Read full reports on Erowid →

    Legal Status

    Country Status Notes
    Canada Legal (OTC/Prescription) Available over-the-counter as oral tablets (commonly sold under brand name Gravol). Injectable formulations require a prescription and have been marketed since 1973.
    United States Legal (OTC/Prescription) FDA approved on May 31, 1972. Oral tablet formulations are available over-the-counter without prescription. Injectable formulations (50 mg/mL intramuscular/intravenous) are available by prescription.

    Harm Reduction

    drugs.wiki

    Dimenhydrinate is a salt that dissociates into diphenhydramine (anticholinergic H1 antihistamine) and 8‑chlorotheophylline (a methylxanthine with adenosine receptor blockade), which can both shape effects and side‑effects. At high doses, users can develop a full anticholinergic toxidrome: agitation, confusion, hallucinations, mydriasis, dry skin/mucosa, urinary retention, hyperthermia, tachycardia, decreased bowel sounds. Onset and peak can be slow (up to ~2–3 hours); redosing early risks stacking and unexpectedly severe delirium. Avoid heat, strenuous activity, or hot environments while intoxicated due to impaired sweating and hyperthermia risk. Do not drive or operate machinery for the rest of the day and potentially the next morning because impairing sedation and vestibular effects may persist beyond the perceived ‘trip.’ People with glaucoma, urinary retention/BPH, or significant pulmonary disease should avoid use without medical supervision due to anticholinergic effects exacerbating these conditions. Children and older adults are more susceptible to delirium, paradoxical excitation, seizures, and serious toxicity; keep products locked away and never use recreationally in these groups. Dimenhydrinate has been associated with QTc prolongation and conduction disturbances at high exposure (largely via diphenhydramine), so avoid combining with other QT‑prolonging drugs and seek care if syncope or palpitations occur. Seizures are a recognized complication of antihistamine toxicity; avoid co‑ingesting agents that lower seizure threshold and seek urgent care if tremor, clonus, or seizure activity appears. If signs of anticholinergic toxicity emerge (confusion, inability to sweat, very hot skin, urinary retention, visual disturbances), seek emergency help; in hospital, benzodiazepines and temperature control are first‑line, and physostigmine may be considered by clinicians for severe pure anticholinergic delirium. Verify the active ingredient on any ‘motion‑sickness’ or ‘original/less drowsy’ products; similarly named brand variants in different markets may contain different actives. Because each 100 mg of dimenhydrinate contains only about 53–55.5 mg of diphenhydramine base, very large ‘recreational’ dimenhydrinate doses can covertly correspond to high diphenhydramine exposure and its cardiotoxic/deliriant risks.

    References

    Data Sources

    Cited References

    Drugs.wiki References

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