Dimenhydrinate

First-generation antihistamine, ethanolamine derivative, antiemetic

ATC code: R06AA02(Diphenhydramine, incl. dimenhydrinate)

Brand names: Dramamine

Updated 24 Sep 2026 · Methodology

Indications

Motion sickness

First line

Dimenhydrinate is the best known remedy for motion sickness: in Spain that means Biodramina and Cinfamar. The AEMPS ficha técnica frames the indication as prevention and treatment of motion sickness symptoms at sea, on land and in the air – nausea, vomiting and dizziness. Children aged 2 to 6 get 12.5 to 25 mg per dose, those aged 7 to 12 get 25 to 50 mg repeated after 6 to 8 hours with a ceiling of 150 mg a day. It must be taken in advance, half an hour before departure: on the road, once nausea has already started, the effect is markedly worse. The 2022 Cochrane review of antihistamines for motion sickness found low-certainty evidence: first-generation antihistamines probably reduce the risk of motion sickness compared with placebo, and no difference between drugs of the class has been shown. Drowsiness is an expected part of the effect, so driving after a dose is unwise.

Sources

ICD-10: T75.3

Marketing claims without evidence base

The drug is promoted for these uses outside international guidelines. Each entry below is analyzed against AEMPS, FDA, EMA, Cochrane and major RCTs.

Vertigo, unspecified

Not recommended

A motion sickness tablet is often kept at home «for dizziness in general». Different kinds of vertigo are treated differently, and dimenhydrinate does not fit all of them. The AEMPS ficha técnica limits the indication to motion sickness symptoms rather than vertigo of any origin. In benign paroxysmal positional vertigo repositioning manoeuvres help, and vestibular suppressants prevent the brain from adapting and drag recovery out. In vestibular neuritis such drugs are used in the first days and stopped early so that compensation is not held back. The dangerous case stands apart: sudden vertigo with double vision, limb weakness, speech disturbance or headache needs urgent care, because it may be a stroke. If dimenhydrinate was prescribed for long-standing dizziness without investigation, consider seeking a second opinion.

Sources

ICD-10: R42 · ICD-11: MB48.0

Insomnia and sleep disorders

Not recommended

The drowsiness from dimenhydrinate is so noticeable that people start taking the tablet instead of a sleeping pill. The drug has no such indication: the AEMPS ficha técnica names motion sickness symptoms only. First-generation antihistamines produce low-quality sleep – REM sleep shortens, grogginess remains in the morning and the effect weakens within a few consecutive nights. The anticholinergic action lies on top: dry mouth, constipation, urinary retention, confusion in older people, worsening of glaucoma. Insomnia is treated differently – it starts with cognitive behavioral therapy and sleep hygiene, and a doctor selects any hypnotic for a short course. The ficha warns separately about porphyria: dimenhydrinate is associated with acute attacks and is considered unsafe in such patients. If motion sickness tablets were recommended as a sleeping aid, consider seeking a second opinion.

Sources

AEMPS: Ficha técnica de dimenhidrinato (2023)

ICD-10: G47.0 · ICD-11: 7A00

How to read tiers A–F

AStrong evidence – first or second line in international guidelines
BRecommended in selected cases
CStudy data contradict each other
DBenefit not proven, no documented harm
FDocumented harm, or risk without benefit

Mechanism of action

Dimenhydrinate is an equimolecular complex of diphenhydramine with 8-chlorotheophylline, and the diphenhydramine part supplies the pharmacological properties. It blocks H1 histamine receptors and carries a marked anticholinergic and sedative action as well. In motion sickness all three properties matter: the drug damps excessive vestibular activity and weakens signal transmission to the vomiting centre, with drowsiness coming along. From this grows the whole profile of cautions in the AEMPS ficha técnica: care in asthma, chronic bronchitis and emphysema because secretions thicken, in prostate enlargement and urinary retention, and in glaucoma. The drug starts working in about 30 minutes, so it is taken in advance, before travel.

Safety

Contraindications

Hypersensitivity to dimenhydrinate and diphenhydramine
Porphyria: the drug is associated with acute attacks
Acute asthma attack
Children under 2 years

Serious adverse effects

Urinary retention in people with prostate enlargement
Worsening of angle-closure glaucoma
Thickening of bronchial secretions in asthma, emphysema and chronic bronchitis
Confusion and falls in older people
Acute porphyria attack

Common adverse effects

Drowsiness and slowed reactions
Dry mouth
Blurred vision
Constipation
Dizziness
Agitation in small children

Pregnancy: can you take Dimenhydrinate?

Studies in rats and rabbits at doses 20 to 25 times the human dose found no harm to the fetus, and adequate controlled studies in humans are lacking. Dimenhydrinate has been used in hyperemesis gravidarum without noticeable adverse effects, yet there are reports of a possible link with uterine contractions when taken late in pregnancy, so the decision rests with a doctor.

Breastfeeding: can you take Dimenhydrinate?

First-generation antihistamines pass into breast milk and cause drowsiness or, conversely, agitation in the infant. While breastfeeding the drug is used only on a doctor's advice and briefly.

Calculate RID

Reference information, not a clinical decision. Discuss feeding pauses or changes with your physician or an IBCLC.

Label mentions4 mentions

Verbatim lines from the interaction sections, in the language of the label

From this drug’s label

Moderateaminoglucósidosclass named in the label
«La administración concomitante de dimenhidrinato con antibióticos del grupo de los aminoglucósidos u otros fármacos ototóxicos puede enmascarar los síntomas iniciales de ototoxicidad, como tinnitus…»
AEMPS, section 4.5 · Open on CIMA
Moderateantidepresivos tricíclicosclass named in the label
«Debido a que el dimenhidrinato tiene efectos anticolinérgicos, potencia los efectos de otros fármacos con actividad anticolinérgica, tales como antidepresivos tricíclicos, IMAO, neurolépticos…»
AEMPS, section 4.5 · Open on CIMA
Moderateantipsicóticosclass named in the label
«Debido a que el dimenhidrinato tiene efectos anticolinérgicos, potencia los efectos de otros fármacos con actividad anticolinérgica, tales como antidepresivos tricíclicos, IMAO, neurolépticos…»
AEMPS, section 4.5 · Open on CIMA
ModerateIMAOclass named in the label
«Debido a que el dimenhidrinato tiene efectos anticolinérgicos, potencia los efectos de otros fármacos con actividad anticolinérgica, tales como antidepresivos tricíclicos, IMAO, neurolépticos…»
AEMPS, section 4.5 · Open on CIMA

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Frequently asked

What is Dimenhydrinate used for?

Dimenhydrinate is evaluated for the following indications with varying evidence strength: Motion sickness (evidence tier B), Vertigo, unspecified (evidence tier D), Insomnia and sleep disorders (evidence tier F). See the full indication matrix with dosing and citations above on this page.

What are the side effects of Dimenhydrinate?

Common side effects of Dimenhydrinate (≥ 1 in 100): Drowsiness and slowed reactions, Dry mouth, Blurred vision, Constipation, Dizziness, Agitation in small children. See the Safety section for uncommon and serious reactions.

Is Dimenhydrinate safe during pregnancy?

Is Dimenhydrinate compatible with breastfeeding?

First-generation antihistamines pass into breast milk and cause drowsiness or, conversely, agitation in the infant. While breastfeeding the drug is used only on a doctor's advice and briefly.

Who should not take Dimenhydrinate?

Dimenhydrinate is contraindicated in: Hypersensitivity to dimenhydrinate and diphenhydramine; Porphyria: the drug is associated with acute attacks; Acute asthma attack; Children under 2 years. Full list in the Safety section.

Official sources

Direct links to regulator labels. Open in a new tab.

AEMPS / CIMA

Other drugs in this group

Diphenhydramine, Doxylamine/pyridoxine, Ebastine, Fexofenadine, Levocetirizine, Rupatadine, Chloropyramine, Ketotifen