Dimenhydrinate (Gravol®) with controlled substances

Controlled Substances

Only midwives who have completed the “Opioids and Benzodiazepines: Safe Prescribing for Midwives” course may independently prescribe controlled substances.. 

(Gravol®) is not a controlled substance but has been included here for reference purposes as it is often given with morphine to counteract the side effects of nausea and vomiting.

Dimenhydrinate is categorized in a class of drugs called antihistamines. It competes with histamine for H1-receptor sites on effector cells in the respiratory tract, gastrointestinal tract and blood vessels; blocks chemoreceptor trigger zones.

Indications and Clinical Use:

Dimenhydrinate can be administered intramuscularly as an analgesic for pain relief in labour and is often given with morphine to counteract the side effects of nausea and vomiting. While it is considered safe, dimenhydrinate may produce some sedation.


Hypersensitivity or previous reactions to dimenhydrinate or any component of the formulation.

Warnings and Precautions:

Use with caution in patients with asthma, peptic ulcer or cardiac arrhythmias and thyroid dysfunction.



Considered low risk in pregnancy, however, exposure near birth of premature infants has been associated with an increased risk of retrolental fibroplasia.


Category L2 – Limited Data– Probably Compatible

Dimenhydrinate is one of the preferred anti-nauseants in lactation; less than 2% of the adult dose of the active ingredient was found in milk and in multiple cases this medication was undetectable. If this medication is used in lactation the lowest effective dose should be given for the shortest possible period of time. The neonate should also be monitored for signs of sedation, such as not waking up to feed at regular intervals.

Adverse Reactions:

Palpitations, hypotension, confusion, nervousness, restlessness, headache, insomnia, tingling, heaviness and weakness of hands, vertigo, dizziness, blurred vision, nasal stuffiness, dryness of nose and throat; nausea, vomiting, diarrhea, constipation, dry mouth; tightness of chest, wheezing.

Dosage and Administration:

Usual Concentration: each ml contains 50 mg

50-100 mg PO every 4-6 hours, maximum dose 400 mg/day

25-50 mg IM or IV every 4 hours, maximum dose 100 mg every 4 hours

25 mg IV should be administered slowly over 2 minutes

Onset of Action:

IM: 20-30 minutes

IV: immediate


IM: 3-6 hours

IV: 3-6 hours