Amoxapine (Asendin)

What it treats

Amoxapine is approved by the U.S. Food and Drug Administration to treat depression, including depression with psychotic features and depression accompanied by anxiety or agitation.

Off-label use is rare today. Off-label means a purpose the label doesn't formally list even though evidence and practice support it.

How it works

Amoxapine is a tetracyclic drug (four fused rings). It affects norepinephrine and, less strongly, serotonin. Its active metabolite (7-hydroxyamoxapine) blocks dopamine D2 receptors in a way similar to first-generation antipsychotics.

That D2 activity is the important distinguishing feature. It gives amoxapine some antipsychotic-like effect (useful in depression with psychosis), but it also brings the movement side effects that antipsychotics can cause.

Receptor mechanism (detail)

Amoxapine is a tetracyclic antidepressant structurally related to the antipsychotic loxapine. It inhibits NET (norepinephrine transporter) and weakly inhibits SERT. Its major metabolite, 7-hydroxyamoxapine, is a D2 receptor antagonist, giving it a first-generation antipsychotic-like profile. It also has H1, alpha-1, and muscarinic blockade, driving sedation, orthostasis, and anticholinergic effects.

Potency and typical dosing pattern

Ranges are typical framework only, not a prescription for any individual.

Starting is 50 mg two or three times a day. Usual range is 200 to 300 mg per day divided; up to 400 mg per day in refractory cases. Doses above 300 mg are typically reserved for inpatient settings.

Safety monitoring

• AIMS (Abnormal Involuntary Movement Scale) at baseline and every 6 months. Amoxapine is the only tricyclic that requires this because of D2 blockade and tardive dyskinesia risk.
• ECG at baseline, and periodically at higher doses. Tricyclics prolong QRS, PR, and QTc.
• Overdose is dangerous. Narrow therapeutic index; even modest overdoses can cause fatal arrhythmias and seizures.
• Watch for parkinsonism, akathisia, dystonia, particularly early on.
• Anticholinergic burden.
• Prolactin may rise (D2 blockade); check if breast tenderness, galactorrhea, or menstrual changes appear.
• Neuroleptic malignant syndrome, rare but possible.
• Orthostatic vitals.
• Suicidality in the first 4 weeks, especially under age 25 (FDA boxed warning).
• Reassess at 2, 4, and 6 to 8 weeks.

What to expect

Common side effects

Common side effects include:

• Drowsiness.
• Dry mouth.
• Constipation.
• Blurred vision.
• Weight gain.
• Dizziness on standing.
• Movement side effects (parkinsonism, akathisia, restless legs, mild tremor).
• Menstrual changes or breast tenderness (from prolactin rise).

If a side effect is severe, or it isn't improving, that's a conversation to have with the prescriber rather than a reason to stop on your own.

Serious side effects and warnings

Serious problems are uncommon, but a few are worth knowing.

Boxed warning. Like all antidepressants, amoxapine carries an FDA boxed warning that it can increase suicidal thoughts and behaviors in children, teenagers, and young adults under 25, especially in the first weeks of treatment or after a dose change.

• Tardive dyskinesia. Long-term D2 blockade can cause involuntary movements of the tongue, face, or limbs that may not fully reverse when the drug is stopped. This is unique to amoxapine among the tricyclics.
• Neuroleptic malignant syndrome. A rare but life-threatening reaction with high fever, muscle rigidity, and altered mental status. It's a medical emergency.
• Effects on heart rhythm. ECG monitoring matters.
• Seizures. Amoxapine lowers seizure threshold, and seizures are a recognized feature of overdose.
• Danger in overdose. Fatal arrhythmias and seizures are both risks.
• Serotonin syndrome. Do not combine with MAOIs.

Sexual side effects

Amoxapine can reduce sex drive and cause erectile difficulty or delayed orgasm. Elevated prolactin (from D2 blockade) can also contribute to sexual side effects and to menstrual changes or breast tenderness.

Weight, appetite, and sleep

Amoxapine can increase appetite and cause weight gain. Its sedating profile means it's often dosed at bedtime for the largest share.

Starting and dosing basics

This section is general background, not a dosing instruction for any individual. The right dose is a decision for a prescriber.

Amoxapine comes as tablets. Starting is low, with steps up over days to weeks. Splitting the dose across the day is standard because of the half-life. A prescriber weighs the movement risk when deciding whether amoxapine is the right medication in the first place, then monitors with AIMS.

Missed doses and interactions

If you miss a dose, take it when you remember, unless it's almost time for the next dose. Skip the missed dose and carry on. Don't take two doses to make up for one.

Interactions matter. Amoxapine must not be combined with MAOI antidepressants, and a gap is needed when switching. Alcohol adds to CNS depression. Other dopamine-blocking drugs (antipsychotics, metoclopramide) stack the movement risk. Give every prescriber and pharmacist a full list of your medications and supplements, including over-the-counter ones.

Stopping and tapering

Amoxapine isn't a controlled substance and isn't habit-forming in the usual sense.

The body does adjust to it, and stopping abruptly can cause discontinuation symptoms. Movement side effects such as tardive dyskinesia may not fully clear on stopping and can even worsen temporarily. A gradual taper planned with a prescriber is the standard.

Pregnancy and breastfeeding

This is an area where individual circumstances matter and the decision belongs with a clinician. Untreated depression carries its own risks during pregnancy. Anyone who is pregnant, planning a pregnancy, or breastfeeding should talk it through with their prescriber so the specific risks and benefits can be weighed for their situation.

Cost and generic availability

Amoxapine is available as a generic. It isn't widely stocked because it isn't commonly prescribed, so a pharmacy may need time to source it.

Common questions

Why does amoxapine cause movement side effects when other antidepressants don't? Its active metabolite blocks dopamine D2 receptors, the same target as antipsychotics. That D2 blockade can cause parkinsonism, akathisia, and tardive dyskinesia.

Why is an AIMS exam part of monitoring? AIMS is the standard tool for tracking involuntary movements. Because amoxapine carries tardive dyskinesia risk (unlike other tricyclics), the check is worth doing at baseline and every 6 months.

Is it still used? Rarely. Newer antidepressants, or an SSRI paired with a low-dose antipsychotic for depression with psychosis, generally do the job with a better side-effect profile.

Is it dangerous in overdose? Yes. Amoxapine overdose can cause both arrhythmias and seizures, and it's on the higher-risk end of tricyclic overdose.

Is it addictive? No. It's not a controlled substance and doesn't cause cravings. Stopping should still be done gradually.

Questions to ask your prescriber

• Why amoxapine specifically, given other options?
• What's the plan for AIMS checks and monitoring movement side effects?
• Which side effects should I call about right away?
• Do we need an ECG at baseline?
• If we decide to stop it later, how would we do that safely?

Sources

This guide draws on current prescribing information and public health references and current as of June 8, 2026. It is reviewed for clinical accuracy and updated as guidance changes.

• U.S. Food and Drug Administration. Amoxapine (Asendin) prescribing information.
• MedlinePlus, U.S. National Library of Medicine. Amoxapine.
• National Institute of Mental Health. Mental health medications.
• American Psychiatric Association. Practice Guideline for the Treatment of Patients with Major Depressive Disorder.
• American Geriatrics Society. Beers Criteria for Potentially Inappropriate Medication Use in Older Adults (2023).