Overview

There is no drug interaction between melatonin and Zyrtec (cetirizine). They are considered safe to take together.

However, both can cause drowsiness. As melatonin is typically taken at night time to help sleep, this usually isn't a concern.

Below, I discuss both medications in more detail.


Melatonin Info

Melatonin is a popular over the counter supplement for use as a sleep aid. Melatonin is not an herbal product, but an endogenous hormone produced by the pineal gland in the brain.

Melatonin has a variety of functions in the body, including:

  • Managing circadian rhythm
  • Immune system modulator
  • Reproductive functioning

Melatonin has conflicting evidence for benefit, but many studies have shown positive effects for the treatment of sleep-cycle disorders and insomnia.

Melatonin levels increase in response to various stimuli (e.g. darkness, time of day) and are thought to play a major role in wakefulness. Melatonin supplementation, therefore, is used to aid in treating issues related to sleep disorders.


Zyrtec Info

Zyrtec is a 'second-generation' antihistamine used for the treatment of seasonal allergies and hives.

When compared to 'first-generation' antihistamines, like Benadryl, 'second-generation antihistamines' have a longer duration of action (around 24 hours) and significantly less sedation. In fact, most 'second-generation' antihistamines are classified as 'non-drowsy', including:

Zyrtec is not classified as non-drowsy as it does cause sedation/drowsiness in around 5-15% of individuals. Nevertheless, the sedation that can occur with it is typically less severe than with 'first-generation' antihistamines.


Melatonin With Zyrtec

As mentioned, there is no interaction between the two. As both can cause sedation and drowsiness, there may be some additive effects. This isn't typically a major concern as melatonin supplementation is generally used in the evening to aid in sleep.


Summary

  • There is no drug interaction between melatonin and Zyrtec, but both can cause drowiness so use caution if taking together.

  • References
    1. Melatonin--the key to the gate of sleep. PubMed
    2. Meta-analysis: melatonin for the treatment of primary sleep disorders. PubMed
    3. The use of Melatonin in children with neurodevelopmental disorders and impaired sleep: a randomised, double-blind, placebo-controlled, parallel study (MENDS). PubMed
    4. Efficacy of melatonin in the treatment of endometriosis: a phase II, randomized, double-blind, placebo-controlled trial. PubMed
    5. A review of the multiple actions of melatonin on the immune system. PubMed
    6. Zyrtec Prescribing Information. AccessFDA