Can scopolamine (anticholinergic) patches and meclizine (antihistamine) be given together?

From the Guidelines

Scopolamine patches and meclizine can be given together, but this combination should be approached with caution due to potential additive side effects. Both medications work to prevent nausea and vomiting but through different mechanisms - scopolamine is an anticholinergic that blocks acetylcholine receptors in the brain, while meclizine is an antihistamine that affects the vestibular system. When used together, patients may experience increased drowsiness, dry mouth, blurred vision, urinary retention, and confusion, as noted in the clinical practice guideline for Ménière's disease 1. This combination may be particularly problematic for elderly patients or those with certain medical conditions like glaucoma, prostatic hypertrophy, or cognitive impairment.

Some key points to consider when using this combination include:

• Monitoring patients for side effects and advising them not to drive or operate machinery until they know how these medications affect them
• Starting with lower doses of each medication to minimize adverse effects
• Informing healthcare providers about all medications being taken to avoid potential drug interactions
• Being aware of the potential for significant toxicity and withdrawal effects when using anticholinergics for more than several days, as mentioned in the guideline 1
• Considering alternative treatment options, such as those outlined in the palliative care guidelines 1, which suggest adding a 5-HT3 antagonist, anticholinergic agent, antihistamine, or cannabinoid if nausea and vomiting persist.

Overall, while scopolamine patches and meclizine can be used together, it is crucial to weigh the potential benefits against the risks and to closely monitor patients for adverse effects, as supported by the most recent and highest quality study 1.

From the FDA Drug Label

1. 1 Drugs Causing Central Nervous System (CNS) Adverse Reactions The concurrent use of scopolamine transdermal system with other drugs that cause CNS adverse reactions of drowsiness, dizziness or disorientation (e.g., sedatives, hypnotics, opiates, anxiolytics and alcohol) or have anticholinergic properties (e.g., other belladonna alkaloids, sedating antihistamines, meclizine, tricyclic antidepressants, and muscle relaxants) may potentiate the effects of scopolamine transdermal system [see Warnings and Precautions (5. 2)].

The use of scopolamine patches and meclizine together may potentiate the effects of scopolamine, increasing the risk of CNS adverse reactions such as drowsiness, dizziness, or disorientation. It is recommended to either choose one of the medications or monitor the patient closely for CNS adverse reactions if concomitant use is necessary 2.

From the Research

Combination of Scopolamine and Meclizine

• The combination of scopolamine patches and meclizine for motion sickness is not directly addressed in most studies, but there are some insights from research on their individual effectiveness and interactions.
• A study from 2011 3 compared scopolamine to other agents, including antihistamines, and found that scopolamine was superior or equivalent as a preventative agent, but the comparisons were limited.
• Another study from 1984 4 directly compared transdermal scopolamine, oral meclizine, and placebo in motion sickness, finding that transdermal scopolamine provided better protection than placebo or meclizine.
• There is no explicit mention of adverse effects from combining scopolamine and meclizine in the provided studies, but it is known that both can cause drowsiness and other side effects, which might be exacerbated when used together 5, 3, 6.
• The safety of using these medications together would depend on various factors, including the individual's health status, the dosage used, and the duration of treatment.

Individual Medication Effects

• Scopolamine is a first-line medication for preventing motion sickness and is administered transdermally several hours before the anticipated motion exposure 5.
• Meclizine, an antihistamine, is also effective in preventing motion sickness, although it may cause sedation 5, 6.
• The effectiveness and safety of double-dose transdermal scopolamine have been evaluated, showing that it may improve treatment without significantly aggravating adverse effects 7.

Considerations for Use

• When considering the use of scopolamine patches and meclizine together, it is essential to weigh the potential benefits against the risks of increased side effects, such as dry mouth, drowsiness, and blurred vision 3, 7, 4.
• Patients should be closely monitored for any adverse effects, and the dosage of each medication should be adjusted accordingly to minimize risks.
• Behavioral and environmental modifications, such as avoiding difficult conditions while traveling or positioning oneself in the most stable part of the vehicle, can also be effective in preventing motion sickness and may be used in conjunction with medication 5, 6.