What percentage of the population metabolizes meclizine (antihistamine) slowly?

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Last updated: July 2, 2025View editorial policy

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From the Research

Approximately 5-10% of the population metabolizes meclizine slowly due to genetic variations in the CYP2D6 enzyme system. These individuals, known as poor metabolizers, process meclizine at a reduced rate compared to the general population. This slower metabolism can lead to higher blood levels of the medication when taking standard doses, potentially increasing the risk of side effects such as drowsiness, dry mouth, and blurred vision.

Key Points to Consider

  • Poor metabolizers may need lower doses of meclizine to avoid these adverse effects.
  • The CYP2D6 enzyme is responsible for breaking down many medications including meclizine, and genetic variations affecting this enzyme are inherited.
  • Ethnicity can influence the prevalence of poor metabolizers, with higher rates observed in certain populations.
  • If you experience unusually strong reactions to standard doses of meclizine, it might indicate you are a slow metabolizer, and you should discuss this with your healthcare provider who may recommend dosage adjustments, as seen in a study on meclizine metabolism and pharmacokinetics 1.

Relevant Studies

  • A study on the pharmacokinetics and safety of meclizine in children with achondroplasia found that meclizine was well tolerated with no serious adverse events 2.
  • Another study found that CYP2D6 is the dominant enzyme for metabolism of meclizine, and its genetic polymorphism could contribute to the large interindividual variability 1.

Clinical Implications

  • It is essential to consider the potential for slow metabolism of meclizine in certain individuals, particularly those with a history of adverse reactions to standard doses.
  • Healthcare providers should be aware of the potential for genetic variations in the CYP2D6 enzyme system and adjust dosages accordingly to minimize the risk of side effects.
  • Further research is needed to fully understand the implications of slow meclizine metabolism and to develop personalized treatment strategies for affected individuals, as suggested by studies on meclizine pharmacokinetics and safety 2, 1.

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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