Mirtazapine is an antidepressant medication that lives a secret double life. Due to its sedating properties, many prescribers use mirtazapine for sleep and to help treat insomnia. However, when using mirtazapine for the treatment of insomnia, prescribers will be using the drug “off-licence.” This is an instance when a side effect of a medication can serve a beneficial purpose, in this case, the drowsiness accompanying mirtazapine.

In this blog, we examine the impact of mirtazapine on sleep and identify individuals who are likely to derive the most benefit from its use. Additionally, we outline the usual dosage of mirtazapine and its potential adverse effects.

What is mirtazapine?

Mirtazapine is primarily prescribed for the treatment of major depression. It falls under the category of atypical antidepressants, typically reserved for cases where standard antidepressants have proven ineffective. Mirtazapine functions by modulating mood through the augmentation of certain neurotransmitters in the brain, such as serotonin.

Since 1996, the FDA has approved the use of mirtazapine in treating depression. Alongside its approved application, mirtazapine has also been prescribed off-label for other conditions, such as:

  • Generalized anxiety disorder
  • Post-traumatic stress disorder
  • Panic disorder
  • Tension-type headaches
  • Fibromyalgia
  • Insomnia

Does mirtazapine affect sleep?

Prescribers noticed that one of the most prevalent side effects of mirtazapine use was increased drowsiness, with up to 53% of individuals experiencing heightened sleepiness upon its administration. This effect is attributed to mirtazapine’s interaction with brain receptors that are responsible for regulating chemicals like serotonin and histamine.

Given its sedative properties, researchers have begun exploring mirtazapine as a potential remedy for sleep disturbances. Mirtazepine could now be offered for those grappling with both depression and sleep issues, while other prescribers have looked into prescribing for insomnia exclusively, even those patients without depression.

Can mirtazapine be used for both insomnia and depression?

The majority of investigations into the impact of mirtazapine on sleep stem from studies involving individuals contending with both sleep disturbances and depression. Insomnia, characterised by difficulties in initiating or maintaining sleep, is frequently observed in individuals with mental health disorders such as depression.

Several studies have indicated positive outcomes regarding mirtazapine’s impact on sleep, demonstrating enhancements in both total sleep duration and improved sleep quality. Mirtazapine is the drug that gives you a two-for-one by alleviating depressive symptoms while simultaneously enhancing sleep. Some experts theorise that a portion of mirtazapine’s efficacy in treating depression may stem from its ability to mitigate sleep disturbances.

A distinguishing advantage of mirtazapine over numerous other antidepressants is its lack of suppression of rapid eye movement (REM) sleep, a phase crucial for cognitive functions like thinking and memory. Nevertheless, it’s worth noting that REM sleep is associated with vivid dreaming, and individuals using mirtazapine have occasionally reported experiencing nightmares.

Mirtazapine for sleep

While expert panels typically advise against using mirtazapine solely to address insomnia in individuals without depression, there are instances where some physicians may opt to prescribe mirtazapine for individuals experiencing insomnia alone.

Limited research exists concerning the impact of mirtazapine on sleep patterns in individuals without depression. In a small-scale study, participants who were administered mirtazapine experienced extended sleep duration and reduced instances of sleep interruptions. Additionally, they demonstrated heightened levels of deep sleep without a decrease in REM sleep.

While generally well-tolerated by most individuals in research trials, mirtazapine can induce side effects. However, due to its limited history in managing insomnia in non-depressed individuals, the American Academy of Sleep Medicine does not incorporate mirtazapine into its standard recommendations for insomnia treatment.

Mirtazapine dosage for sleep

The dose of mirtazapine is usually 7.5mg or 15mg when it is used exclusively for insomnia without any pre-existing depression. At these dosage levels, mirtazapine often induces more drowsiness compared to higher doses of the medication.

Typically, mirtazapine is taken once daily before bedtime, either as a tablet to be swallowed or as a tablet that disintegrates in the mouth.

How long does it take for mirtazapine to start working?

For specific individuals, the sleep-promoting effects of mirtazapine can manifest within one or two days of initiating the medication. However, when utilised for depression, mirtazapine may require several weeks before any discernible effects are observed.

Side effects of mirtazapine

Similar to many medications, mirtazapine may induce various side effects. Among the most prevalent side effects is fatigue or drowsiness, which is a side effect we are actually exploiting when using it for insomnia. Other commonly reported side effects associated with mirtazapine across multiple research studies include:

  • Dry mouth
  • Increased appetite
  • Weight gain
  • Dizziness

Additional side effects that can occur when taking mirtazapine include:

  • Confusion
  • Anxiousness
  • Constipation
  • Nausea and vomiting

While rare, mirtazapine may result in potentially severe side effects. It is crucial to seek immediate medical attention if experiencing:

  • Chest pain
  • Rapid heartbeat
  • Seizures
  • Fever, chills, or other flu-like symptoms

Similar to several antidepressants, the FDA cautions that individuals under 24 years old taking mirtazapine may have an increased risk of experiencing suicidal thoughts. Although rare, this necessitates prompt attention from a medical professional, mental health expert, or suicide prevention service.

Furthermore, sudden cessation of mirtazapine can result in withdrawal symptoms, including:

  • Depression
  • Panic attacks
  • Insomnia
  • Gastrointestinal distress

For this reason, anyone planning to stop taking mirtazapine should consult with a doctor about how to gradually discontinue its use.

To discuss if mirtazapine may be an option for you to help with you insomnia, please complete the treatment consultation form to book an appointment with Dr Zak Taylor.

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