Can Phenergan (promethazine) be used to treat motion sickness?

Promethazine (Phenergan) for Motion Sickness

Yes, promethazine (Phenergan) is effective for treating motion sickness and is FDA-approved for this indication with a recommended dosage of 25 mg taken twice daily. 1

Dosage and Administration

• For motion sickness, the average adult dose is 25 mg taken twice daily. The initial dose should be taken 30-60 minutes before anticipated travel and repeated 8-12 hours later if necessary 1
• On subsequent travel days, 25 mg should be taken upon waking and again before the evening meal 1
• For children, the dosage ranges from 12.5 to 25 mg twice daily, administered orally 1

Mechanism of Action

• Promethazine is a phenothiazine with antihistaminic properties that suppresses the central emetic center to relieve nausea and vomiting associated with motion sickness 2
• It has multiple mechanisms of action including antihistamine (H1), anticholinergic, and sedative effects that help address the neural pathways involved in motion sickness 3

Efficacy

• Promethazine has been shown to be effective in relieving symptoms of severe motion sickness 4
• Studies have demonstrated that intramuscular injections of promethazine (50 mg) can greatly relieve symptoms in severely motion sick individuals 4
• It has also been successfully used to treat space motion sickness in astronauts, with immediate symptom relief reported in the majority of cases 5

Important Considerations

• Promethazine may cause drowsiness, which could impair the ability to perform activities requiring mental alertness 3
• Some individuals may experience nervous excitation, dry mouth, and fatigue as side effects 3
• The medication can affect optokinetic nystagmus and may interfere with visual fixation during motion, which could be relevant for activities requiring visual acuity 6

Contraindications

• Promethazine is contraindicated for children under 2 years of age due to the risk of respiratory depression 1
• Caution should be exercised in patients with a history of seizures, narrow-angle glaucoma, or prostatic hypertrophy due to its anticholinergic effects 2

Alternatives for Motion Sickness

• Other options for motion sickness include:
  • Antihistamines like meclizine 7
  • Anticholinergics such as scopolamine, which blocks acetylcolina and helps reduce neural mismatch 2
  • Non-pharmacological approaches like proper positioning, focusing on the horizon, and avoiding reading while in motion 2

Potential Pitfalls

• Long-term use of vestibular suppressants like promethazine is not recommended as they may interfere with central compensation mechanisms for vestibular disorders 7
• Promethazine may delay gastric emptying, which could be a consideration for patients with gastroparesis 8
• Elderly patients may be at increased risk for falls due to the sedative and anticholinergic properties of the medication 2

In summary, promethazine is an effective and FDA-approved medication for the prevention and treatment of motion sickness when used at appropriate dosages. Its multiple mechanisms of action make it particularly useful for this indication, though patients should be counseled about potential side effects, particularly drowsiness.