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Side Effects of Amoxapine (Asendin)


Amoxapine (brand name Asendin) is an antidepressant drug of the class “tricyclic antidepressants” (TCAs) that is used to treat major depressive disorder (MDD), agitation, or anxiety disorders (e.g. panic disorder) and bipolar disorder.

Serious Side Effects of Amoxapine

Suicide ideation may occur, especially if you are younger than 24 years old. Immediately contact your healthcare provider if you develop any of the following symptoms: suicide ideation or attempts to commit suicide; anxiety; depression; panic attacks; trouble sleeping; acting on dangerous impulses; irritability; feeling very agitated or restless; being angry or violent; acting aggressive, an extreme increase in activity and talking (mania); or other unusual changes in behavior or mood.


If you have bipolar disorder (manic-depression) or schizophrenia or a history of mental illness or psychosis, you may be more prone to suicidal thoughts or behavior. If you have any of these conditions, tell your doctor to see if Asendin/amoxapine is right for you.


Other serious side effects of amoxapine include liver damage, neutropenia (low white cell count) and lymphopenia (low level of lymphocytes).

Risk of Akathisia

Never take amoxapine in larger amounts, or for longer than recommended by your doctor as it can cause a serious movement disorder that may not be reversible. Symptoms of this disorder include tremors or other uncontrollable muscle movements.

Common Side Effects of Amoxapine

According to the FDA, common side effects of amoxapine include: constipation, dry mouth, feeling sleepy, anxiety, vision problems, confusion, dizziness, headaches, edema, fatigue, nausea, nervousness/restlessness, prolactin levels increases, rash, sweating, tremor, or weakness (Amoxapine label, FDA reporting).

Drug Interactions

Inform your doctor about all your medical conditions, particularly if you are taking an antidepressant known as an SSRI (selective serotonin reuptake inhibitor) such as citalopram (Celexa), escitalopram (Lexapro), fluoxetine (Prozac), fluvoxamine (Luvox), paroxetine (Paxil), or take sertraline (Zoloft) in the past 5 weeks; heart rhythm medications; bladder or urinary medicines; bronchodilators; cold or allergy medicine that contains an antihistamine; medication for Parkinson’s disease or medications to treat excess stomach acid, stomach ulcer, motion sickness, or irritable bowel syndrome.


Discuss with your doctor before combining amoxapine with other medications. Sleeping pills, narcotic pain medicines, muscle relaxers, or medicines for anxiety, depression, or seizures can worsen the sedative (“feeling sleepy”) side effect of amoxapine.


Like other similar antidepressants, amoxapine is metabolized in the body mainly by CYP2C19 and CYP2D6. Their genetic variations can have effects on its clinical response, including adverse reactions. Although no specific recommendation for amoxapine is in place, pharmacogenetic testing used to identify individuals with varying activity of CYP2C19 and CYP2D6 has great merit. (Pediatrics, “Pharmacogenetics for Safe Codeine Use in Sickle Cell Disease,” Jul 2016).

When to Contact Your Doctor

The FDA recommends discussing with your doctor what possible effects might be caused when taking amoxapine. You should immediately contact your doctor if you develop skin rash with fever; uncontrolled muscle movements in your face (chewing, tongue movement, frowning, blinking or eye movement); pounding heartbeats or fluttering in your chest; little or no urination; chest pain or pressure, sudden numbness or weakness (especially on one side of the body), pain spreading to your jaw or shoulder; problems with vision or balance; slurred speech, high fever, severe nervous system reaction–very stiff (rigid) muscles, fast or uneven heartbeats, sweating, confusion, tremors and feeling as though you might pass out (Amoxapine label as reported by the FDA.

About Pharmacogenetic Testing

Many patients do not suffer from adverse reactions when taking amoxapine. However, some patients will suffer multiple severe drug reactions. This inter patient variability is significantly accounted for the differences in genetics between patients. Polymorphisms in the genes and enzymes that interact with amoxapine results in varied reactions to the drug between patients.


Amoxapine is metabolized in the liver by the hepatic cytochrome P450 system (a superfamily of enzymes involved in 75% of all drug metabolism). Alleles in the cytochrome P450 enzymes that metabolize amoxapine could result in an increased probability of developing side effects when taking the drug.


Therefore, identifying these polymorphisms can aid in clinical decision making. For instance, if a clinician knows a patient has a given allele in the enzymes that metabolize amoxapine, they may prescribe a different drug or alter the starting dose. This can reduce side effects associated with amoxapine.

Know Your Risk of Side Effects with the Rxight® Genetic Test

Rxight®, a genetic test by MD Labs, examines how an individual is likely to respond to hundreds of clinically relevant medications (including amoxapine). MD Labs also utilizes state-of-the-art technology to test for 60 alleles on 21 genes to see how a patient metabolizes over 200 medications. The Rxight® pharmacogenetic program helps healthcare providers create an individualized treatment plan. Rxight® assists in developing an effective medication treatment plan that gets patients on the right medication, minimize, and prevent side effects.


Call us for more information about MD Labs, Rxight®, or pharmacogenetics at 1-888-888-1932 or email us at support@Rxight.com.


Contributors to this Article:
Michael Sapko, MD, PhD; Deborah Kallick, PhD, Medicinal Chemistry


Read more about Rxight® Genetic Testing for Medications