Side Effects of Meclizine
Meclizine commonly causes drowsiness, dry mouth, headache, and fatigue, with rare occurrences of blurred vision and anaphylactic reactions. 1
Primary Adverse Effects
According to the FDA drug label, the most frequently reported side effects of meclizine include: 1
- Drowsiness (most common sedating effect)
- Dry mouth (anticholinergic effect)
- Headache
- Fatigue
- Vomiting
- Blurred vision (rare but documented)
- Anaphylactic reaction (rare but serious)
Comparative Side Effect Profile
Research comparing meclizine to other antivertigo medications demonstrates that meclizine produces primarily sleepiness as its main side effect, with a more favorable profile than many alternatives. 2 In controlled studies, meclizine showed:
- Increased sleepiness (consistently reported) 2
- Impaired accuracy on short-term memory tasks 2
- Similar rates of fatigue and headache compared to thiethylperazine 3
- Fewer side effects than baclofen (which causes sleepiness, tiredness, blurred vision, concentration problems, and dizziness) or promethazine combinations (which cause dry mouth, dizziness, vertigo, confusion, insomnia, and tremors) 2
When compared to transdermal scopolamine, meclizine produced fewer anticholinergic side effects, particularly less dry mouth. 4
Critical Safety Concern: Fall Risk
A major concern with meclizine use is the significantly increased risk of injurious falls, even in younger adults. 5 Recent large-scale cohort data shows:
- 9% of patients prescribed meclizine experienced falls requiring medical evaluation 5
- Among patients aged 18-64 years: hazard ratio of 2.94 (95% CI, 2.81-3.08) for falls 5
- Among patients aged ≥65 years: hazard ratio of 2.54 (95% CI, 2.42-2.66) for falls 5
This fall risk persists for 60 days after prescription and represents a critical safety consideration that outweighs the medication's antivertigo benefits in many clinical scenarios. 5
Mechanism of Side Effects
The side effects stem from meclizine's H1 receptor antagonism and anticholinergic properties. 1 As a histamine H1 receptor antagonist, it crosses the blood-brain barrier causing central nervous system depression (drowsiness, fatigue), while its anticholinergic effects produce dry mouth and blurred vision. 1
Special Populations and Warnings
Patients should be explicitly warned that meclizine may impair their ability to operate machinery or vehicles due to its sedating effects. 1 The drug label specifically advises:
- Caution in patients with renal impairment (potential for drug accumulation) 1
- Caution in elderly patients (declining renal function with age) 1
- Variable effects based on CYP2D6 genetic polymorphism (monitor for adverse reactions accordingly) 1
- Alcohol increases adverse reactions and should be avoided 1
Clinical Context
While meclizine has historically been widely prescribed for vertigo and motion sickness, its use is increasingly recognized as guideline-discordant care for common vestibular diagnoses, particularly given the substantial fall risk that extends well beyond the immediate treatment period. 5