What is the drug Avanza used for? Mirtazapine's Approved and Off-Label Applications

October 7, 2025 •

5 min read

In some countries, such as Australia and New Zealand, Avanza is the brand name for the antidepressant mirtazapine, a drug known as Remeron in the U.S. and other regions. So, what is the drug Avanza used for? Its primary indication is major depressive disorder, but its unique pharmacological profile also makes it a valuable tool for treating related symptoms like insomnia and loss of appetite.

Quick Summary

Avanza, the brand name for mirtazapine, is a tetracyclic antidepressant prescribed for major depressive disorder. It is also used off-label for conditions such as insomnia, anxiety disorders, and increasing appetite.

Key Points

Approved for Major Depressive Disorder (MDD): Avanza, or mirtazapine, is officially prescribed for treating moderate to severe depression.
Used Off-Label for Insomnia: Its sedative effects, particularly at lower doses, make it a useful off-label treatment for insomnia and sleep disturbances.
Increases Appetite and Weight Gain: A common side effect is increased appetite, which can be therapeutically beneficial for patients with depression-related weight loss or anorexia.
Useful for Anxiety and Depression : The medication is often a good option for depressed patients with significant anxiety, and is used off-label for various anxiety disorders.
Different Mechanism of Action: As a Noradrenergic and Specific Serotonergic Antidepressant (NaSSA), it works differently than SSRIs and has a different side effect profile.
Requires Gradual Discontinuation: To prevent withdrawal symptoms, stopping the medication requires a gradual reduction in dosage under a doctor's supervision.
Risk of Suicidal Thoughts: Like many antidepressants, it carries a boxed warning for an increased risk of suicidal thoughts, especially in younger adults.

Understanding Avanza: The Brand Name for Mirtazapine

For many, the name Avanza is less familiar than its generic counterpart, mirtazapine, or the U.S. brand name, Remeron. This medication is classified as a tetracyclic antidepressant and operates differently from the more common Selective Serotonin Reuptake Inhibitors (SSRIs). Its unique mechanism of action makes it particularly beneficial for patients who experience certain co-occurring symptoms with depression, such as sleep disturbances and appetite loss. However, it is crucial to consult a healthcare professional to understand the appropriate use, benefits, and risks associated with Avanza.

Primary Medical Use: Major Depressive Disorder

Avanza's primary, FDA-approved use is the treatment of Major Depressive Disorder (MDD) in adults. It works by influencing the balance of specific neurotransmitters in the brain, particularly noradrenaline and serotonin. Unlike other antidepressants, it increases the activity of these chemicals by blocking certain receptors rather than inhibiting reuptake. Clinical trials have shown its efficacy in improving depressive symptoms, with some patients noticing improvement within the first couple of weeks, though the full effect can take four to six weeks to manifest.

Avanza may be particularly beneficial for treating specific symptoms of depression, including:

Significant anxiety: Mirtazapine has been shown to be especially helpful for depressed patients experiencing significant anxiety.
Insomnia: As it has a sedative effect, Avanza is useful for individuals with depression who have trouble sleeping.
Poor appetite or weight loss: One of the drug's side effects is an increase in appetite and subsequent weight gain, which can be beneficial for those struggling with appetite loss due to depression.

Off-Label Uses of Avanza (Mirtazapine)

Beyond its approved indication, Avanza is frequently prescribed for several off-label conditions. It's important to note that off-label use means the drug is prescribed for a purpose for which it was not originally approved, and it should be done under a doctor's guidance.

1. Insomnia

Due to its strong sedative properties, Avanza is often used at low doses to treat insomnia, even in patients without depression. It blocks histamine H1 receptors, similar to how sedating antihistamines work, which causes drowsiness. This can help patients fall asleep faster and improve overall sleep quality.

2. Anxiety Disorders

Some studies support the use of Avanza for various anxiety disorders, including Generalized Anxiety Disorder (GAD), Social Anxiety Disorder, and Panic Disorder. It is sometimes used as a treatment alternative when first-line options like SSRIs prove ineffective or intolerable.

3. Appetite Stimulation and Weight Gain

Avanza can cause increased appetite and weight gain, a side effect leveraged for therapeutic purposes. It is sometimes used for patients experiencing anorexia nervosa or other medical conditions causing significant weight loss, such as cancer.

4. Post-Traumatic Stress Disorder (PTSD)

In some cases, particularly in combination with other medications like SSRIs, Avanza has been used to help manage symptoms of PTSD.

Mechanism of Action: How Avanza Works

Mirtazapine's therapeutic effects stem from its unique mechanism as a Noradrenergic and Specific Serotonergic Antidepressant (NaSSA). It enhances the availability of key brain chemicals in a novel way compared to other antidepressants. The main actions include:

Alpha-2 Adrenergic Receptor Blockade: Avanza blocks presynaptic alpha-2 adrenergic receptors, which increases the release of both norepinephrine and serotonin.
Serotonin Receptor Antagonism: By blocking specific serotonin receptors (5-HT2 and 5-HT3), Avanza reduces certain side effects associated with other antidepressants, such as anxiety, insomnia, and nausea.
Histamine H1 Receptor Blockade: This action is responsible for the drug's powerful sedative and appetite-stimulating effects.

Side Effects and Risks of Avanza

As with all medications, Avanza carries the potential for side effects. Many are mild and improve with continued use, but some can be serious.

Common Side Effects:

Drowsiness or sleepiness
Increased appetite and weight gain
Dizziness
Dry mouth
Constipation
Headaches

Serious Side Effects:

Suicidal Thoughts: A boxed warning indicates an increased risk of suicidal thoughts and behavior, especially in young adults (under 25) at the start of treatment or following dose changes.
Serotonin Syndrome: Risk is increased when combined with other serotonergic drugs or MAOIs.
Blood Cell Abnormalities: Rare but serious side effects include a temporary shortage of white blood cells (granulocytopenia).
Angle-Closure Glaucoma: The medication may cause an increase in eye pressure.

Avanza (Mirtazapine) vs. Common SSRIs


Feature	Avanza (Mirtazapine)	Common SSRIs (e.g., Sertraline, Fluoxetine)
Mechanism of Action	NaSSA: Blocks alpha-2, 5-HT2, 5-HT3, and H1 receptors.	SSRI: Blocks reuptake of serotonin, increasing its availability.
Primary Use	Major Depressive Disorder.	Major Depressive Disorder, and various anxiety disorders.
Effect on Sleep	Often causes drowsiness; can improve sleep patterns, including reduced sleep latency.	Can cause sleep disturbances like insomnia or agitation, though effects vary.
Effect on Appetite & Weight	Tends to increase appetite and cause weight gain.	Can cause appetite changes; some may experience a decrease, others an increase.
Effect on Sexual Function	Less likely to cause sexual dysfunction compared to SSRIs.	Can frequently cause sexual side effects.
Onset of Action	Faster onset for some symptoms like sleep and anxiety (within 1-2 weeks), but full antidepressant effect takes longer.	Typically takes several weeks to show noticeable improvements.
Common Side Effects	Drowsiness, dizziness, weight gain, dry mouth.	Nausea, headache, insomnia, nervousness, sexual dysfunction.

Conclusion

Avanza (mirtazapine) is a distinct and effective antidepressant for treating Major Depressive Disorder, particularly for patients who also suffer from insomnia, anxiety, or appetite loss. Its unique pharmacological action provides a different side effect profile compared to other antidepressants, notably a lower risk of sexual dysfunction but a higher likelihood of sedation and weight gain. The decision to use Avanza, especially for off-label purposes, should always be made in consultation with a healthcare provider, who can weigh the potential benefits against the risks for your specific circumstances. Patients should be aware of the serious potential for suicidal ideation, especially early in treatment, and the gradual tapering required to discontinue the medication.

Important Considerations for Safe Use

Do not stop taking Avanza suddenly without talking to your doctor, as this can cause withdrawal-like symptoms.
Avoid alcohol while on this medication, as it can increase drowsiness and impair alertness.
Inform your doctor about all other medications and supplements you are taking to avoid dangerous drug interactions, especially with MAOIs or other serotonergic drugs.
Monitor for changes in mood, behavior, or suicidal thoughts, particularly at the beginning of treatment or after dosage adjustments, and report them to your doctor immediately.

For more detailed information, consult the MedlinePlus drug information page for mirtazapine, the generic name for Avanza.

Frequently Asked Questions

Avanza is a brand name for the generic drug mirtazapine used in some countries like Australia and New Zealand. Remeron is the brand name for mirtazapine in the U.S. and other regions. They contain the same active ingredient and have the same uses and effects.

While some improvements in sleep and anxiety may be noticed in the first one to two weeks, the full antidepressant effect of Avanza can take four to six weeks to become apparent. Patients should not get discouraged or stop the medication prematurely.

Yes, Avanza is often prescribed off-label at a low dose (e.g., 7.5mg or 15mg) specifically for insomnia, due to its sedative effects caused by blocking histamine receptors. This is typically for patients who do not have depression.

Yes, increased appetite and weight gain are well-known side effects of Avanza (mirtazapine). This is because the drug blocks histamine H1 receptors, which can stimulate appetite.

Abruptly stopping Avanza is not recommended and can lead to withdrawal-like symptoms such as anxiety, dizziness, headaches, and nausea. A doctor will typically prescribe a gradual reduction in dosage to safely discontinue the medication.

It is advised not to drink alcohol while taking Avanza. Combining alcohol with this medication can significantly increase sleepiness and sedation, impairing alertness and potentially leading to dangerous consequences.

Avanza (mirtazapine) has a different mechanism than SSRIs, giving it a distinct side effect profile. It is more likely to cause sedation and weight gain but less likely to cause sexual dysfunction compared to many SSRIs.