Antihistamine / antiemetic (theoclate salt of diphenhydramine)

Dimenhydrinate

Brand names: Dramamine

Dimenhydrinate is a sedating first-generation antihistamine used to prevent and treat nausea, vomiting and vertigo, particularly motion sickness.

Dosing — being independently re-sourced

ClinCalc Pro is rebuilding its dose data from primary open sources — the manufacturer SmPC (eMC), the WHO Model Formulary and other official references — under clinician review. This drug's structured dose is not yet published here. Confirm all doses against the product SmPC and your local formulary before prescribing.

Clinical monograph

How it works

Through its diphenhydramine component it antagonises histamine H1 receptors and has central anticholinergic activity, reducing vestibular stimulation and the emetic response.

Prescribing in practice

It commonly causes drowsiness and patients should be warned not to drive or operate machinery until they know how it affects them.
Anticholinergic effects mean caution in the elderly and in conditions such as glaucoma, prostatic enlargement and urinary retention.
For motion sickness it is more effective taken before travel than once symptoms are established.

Monitoring

No laboratory monitoring is required; review effectiveness and anticholinergic side effects clinically.

Counselling the patient

Take before travelling to prevent motion sickness.
Expect drowsiness and avoid driving and alcohol.
Seek advice before use if you have glaucoma or difficulty passing urine.

Evidence & guidelines

Antihistamines are an established option for the prevention of motion sickness and symptomatic relief of vertigo.

Reference: SmPC Dramamine; NICE CKS Vertigo; NHS Travel Health; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways