Seroquel® vs. Zyprexa®

As a group of medications used to treat clinically diagnosed psychotic disorders (i.e., mental/mood disorders), antipsychotics are regularly prescribed for conditions including schizophrenia, major depressive disorder, and various forms of psychosis. Seroquel and Zyprexa are two medications that fall into the classification of antipsychotics; both drugs may help individuals who need them achieve reduced psychotic symptoms such as hallucinations, major depression, delusions, and manic and depressive episodes. In the United States alone, about 7 million people take antipsychotic medications such as Seroquel and Zyprexa to help manage their symptoms. There are benefits and potential drawbacks to using each, some of which we will cover below. Continue reading to learn about what Seroquel and Zyprexa are, how Seroquel and Zyprexa differ from one another and how they are similar, and how DNA testing can help you decide whether Seroquel or Zyprexa may be better for you.

Seroquel vs Zyprexa: What are They?

According to the National Institute of Mental Health, about three out of every 100 people will experience a form of psychosis at some point in their lives. The term “psychosis” may refer to hallucinations (such as hearing, seeing, smelling, tasting, or having a sensation about something that is not real or present) but could also include paranoia, delusions, and disordered thoughts and speech. Medications such as Seroquel and Zyprexa were developed to address the parts of the brain associated with hallucinogenic thoughts and psychosis and help reduce or eliminate them. There are various ways to treat psychosis; some people seek talk therapy in the form of cognitive behavioral therapy (CBT) with individual or group therapy. Others layer on antipsychotic medications such as Seroquel or Zyprexa.

Both Quetiapine (Seroquel) and Olanzapine (Zyprexa) may be helpful for the aforementioned conditions and the symptoms associated with them, but how they interact with individuals depends on individualized metabolisms, body chemistry makeup, and many other factors.

Prior to embarking on any antipsychotic medication journey, it is important to understand the nuances between the drugs you are considering. Knowing the differences between Seroquel and Zyprexa is crucial for helping individuals make educated decisions about which one will be best for them. Let’s take a closer look at how each of these antipsychotic medications works.

What is Seroquel?

Quetiapine (Seroquel) is an atypical antipsychotic medication (also known as a second-generation antipsychotic) that is primarily used for certain mood disorders such as schizophrenia, bipolar disorder, and mania or clinical depression associated with bipolar disorder. When used for the adjunctive treatment of major depressive disorder (MDD), Seroquel should be taken in conjunction with an antidepressant. Seroquel works by helping restore the balance of certain neurotransmitters in the brain. It may help decrease the presence of hallucinations and improve concentration in individuals with the aforementioned diagnoses, as well as improve mood swings, sleep, appetite, and energy levels.

What is Zyprexa?

Olanzapine (Zyprexa) is also a mental health medication that falls under the class of drugs called atypical antipsychotics. Zyprexa is primarily used to treat mood disorders that include but are not limited to schizophrenia and bipolar disorder. Olanzapine’s resemblance to dopamine and serotonin work to help improve thinking, mood, and behavior in individuals diagnosed with the aforementioned conditions. Just like Seroquel, Zyprexa is also recognized as a second-generation antipsychotic (SGA).

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Seroquel vs Zyprexa: Common Side Effects

Introducing a new medication of any kind into your system comes with an increased risk of side effects, some of which may be averse to individuals. How you experience side effects from an antipsychotic medication depends on a variety of factors, some of which include your body chemistry and makeup, weight, other medications you may be taking, and your mental and medical condition. Read on to learn about some of the most common side effects users experience when taking Seroquel and Zyprexa.

Side Effects Common with Seroquel

Some people who take Seroquel report the following side effects:

  • Increased blood pressure
  • Increased heart rate
  • Drowsiness
  • Headaches
  • Agitation
  • Dizziness
  • Fatigue
  • Involuntary movements (extrapyramidal symptoms)
  • Weight gain
  • Cholesterol changes
  • Increased glucose levels
  • Dry mouth
  • Increased appetite
  • Constipation

Side Effects Common with Zyprexa

Taking Zyprexa may come with certain side effects, some of which include:

  • Low blood pressure
  • Drowsiness
  • Involuntary movements (extrapyramidal symptoms)
  • Restlessness
  • Dizziness
  • Headaches
  • Fatigue
  • Insomnia
  • Weight gain
  • Increased appetite
  • Dry mouth
  • Indigestion
  • Constipation
  • Liver function test abnormalities
  • Weakness
  • Accidental injury

In rare cases, second-generation antipsychotics such as Seroquel and Zyprexa may also increase the levels of the hormone prolactin, which could cause females to develop amenorrhea and men to lose their sex drive or experience erectile problems. Some people also report side effects related to muscle movement including extrapyramidal symptoms (EPS) and tardive dyskinesia (TD). These may present as restlessness, tremors, stiffness, jerky movements, tongue rolling, and chewing movements. Taking second-generation antipsychotics (SGAs) comes with an increased risk of metabolic syndrome, which may present as weight gain, high blood pressure, and high cholesterol.

Seroquel vs Zyprexa: Forms and Dosage

Seroquel Dosage

This drug should always be taken exactly as prescribed by your doctor. Seroquel is available in tablet (immediate release) form as well as in extended-release tablet form as Seroquel XR. Seroquel comes in various strengths including 25 mg, 50 mg, 100 mg, 200 mg, 300 mg, and 400 mg. Seroquel XR is available in 50 mg, 150 mg, 200 mg, 300 mg, and 400 mg strengths.  Most patients take Seroquel or its generic version Quetiapine 1, 2, or 3 times per day either with or without food. Seroquel extended release can be taken without food or with a light meal.

Zyprexa Dosage

Zyprexa should always be taken exactly as prescribed by your healthcare provider. Zyprexa is available in four forms: tablet, orally disintegrating tablet, immediate-release injection, and extended-release injection. Zyprexa tablets come in 2.5 mg, 5 mg, 7.5 m, 10 mg, 15 mg, and 20 mg strengths. Zyprexa Zydix® (the orally disintegrating tablets) comes in 5 mg, 10 mg, 15 mg, and 20 mg strengths. Immediate-release Zyprexa is available in 10 mg vials. Zyprexa Relprevv® (extended-release injection) is available in 150 mg, 210 mg, 300 mg, and 405 mg strengths.

Most patients take Zyprexa tablets 1 time per day with or without food. Your doctor may start you on a low dose of the medication and increase it slowly over the course of several weeks. Orally disintegrating tablets must remain in their original packaging until immediately before use.

The long-acting injection form of Zyprexa will typically be administered by a healthcare professional every 2-4 weeks.

Seroquel vs Zyprexa: How Long Does It Take to Start Working?

How long it takes for Seroquel or Zyprexa to start working depends on a variety of factors, some of which include age, weight, metabolism, and condition. Most people begin to see results within 1 to 2 weeks of starting treatment with Seroquel, with the majority of individuals reporting noticeable results after 2-3 months. In the first 1-2 weeks of treatment, you can expect to see improvement in hallucinations, disorganized thinking, delusions, motivation, and social interaction tendencies. While hallucinations and delusions may improve, they do not always go away completely.

Similar to Seroquel, Zyprexa typically starts to take effect within 1 to 2 weeks of beginning treatment, with the most noticeable effects becoming apparent within 2-3 months. Most people continue to see improvement throughout the first 3 to 4 months of taking Zyprexa.

Regardless of whether you take Seroquel or Zyprexa, the time it takes to see effects will vary for all individuals.

Seroquel vs Zyprexa: Drug Interactions

There are certain medications that are not recommended to be taken with others given the way they may interact. It is always advisable to speak with your doctor and/or pharmacist prior to mixing medications.

Seroquel may block the effectiveness of medications such as levodopa/carbidopa (Sinemet®), bromocriptine, pramipexole (Mirapex®), and ropinirole (Requip®), which are commonly used to treat Parkinson’s disease. Additionally, taking Seroquel with other antipsychotics and antiarrhythmics may increase the risk of heart problems.

Zyprexa may lower your blood pressure, which means it is best to avoid taking other blood-pressure-lowering medications (i.e., propranolol or Inderal®) while on this drug. Taking sedatives such as lorazepam (Ativan®) and diazepam (Valium®) may increase the risk of fatigue or dizziness when used with Zyprexa. This risk increases when the injection form of Zyprexa.

Smoking cigarettes may decrease the levels of Olanzapine (generic form of Zyprexa) and make it less effective.

Seroquel and Zyprexa should not be taken together as doing so may increase the levels and effects of each drug beyond the prescribed and intended amount.

Seroquel vs Zyprexa: Which One Should I Take?

Whether you take Seroquel vs Zyprexa depends on a variety of factors, all of which should be evaluated by you and your healthcare provider prior to starting treatment. The primary reason to take Seroquel vs Zyprexa or vice versa is use. The two drugs are both FDA-approved for schizophrenia and bipolar disorder, but each have different off-label uses that may be more suitable to certain individuals. You and your doctor should discuss your condition to determine which medication will be most suitable for you. Pharmacogenetic testing for medication may also help.

Some people prefer Zyprexa to Seroquel because Seroquel has to be taken multiple times per day, while Zyprexa is a once-daily medication. Additionally, Zyprexa comes in more forms than Seroquel, some of which may be favorable based on preference or ingestion method.

It is important to note that the various forms of Zyprexa come with an increased risk of certain side effects, especially for Zyprexa Relprevv (extended release injection form). Although rare, these side effects include post-injection delirium/sedation akin to an overdose. Patients may also find that taking Zyprexa in its injectable form is more of a hassle because injections must be performed at a registered healthcare facility. Furthermore, patients need to be observed for at least 3 hours post injection.

Please note that the long acting injection Zyprexa Relprevv is only available through Zyprexa Relprevv Patient Care program, a restricted distribution program.

Seroquel vs Zyprexa: Similarities and Differences




Drug group

Atypical Antipsychotic/ Second-Generation Antipsychotic (SGA)

Atypical Antipsychotic/ Second-Generation Antipsychotic (SGA)

FDA Approved Uses

Schizophrenia, bipolar disorder, major depressive disorder (MDD).

Schizophrenia, bipolar disorder, major depressive disorder (MDD).

Off-Label Uses

Delusional parasitosis, posttraumatic stress disorder (PTSD), generalized anxiety disorder, delirium, obsessive compulsive disorder (OCD).

Chemotherapy-associated nausea or vomiting, delirium, delusional parasitosis, posttraumatic stress disorder (PTSD), Tourette’s syndrome.

Intended duration of use



Available in generic form 



May be habit forming?



Available forms

Tablet and extended release tablet. 

Tablet, orally disintegrating tablet, immediate release injection, and extended release injection.

Safe for use while pregnant?

Potential risks during the third trimester. 

Potential risks during the third trimester. 

Safe for use with alcohol?

Not recommended

Not recommended

ClarityX: DNA Testing for Medication

The DNA in our bodies contains valuable information that may be useful to determine how we will respond to certain medications. ClarityX examines DNA to uncover this information and provide patients with detailed reports on how they may react to taking certain drugs. We look for variations with the cytochrome P450 enzymes (which metabolize over 70% of drugs), including the enzymes CYP3A4, CYP2D6, and CYP1A2  that are responsible for how you may react to Seroquel and Zyprexa . ClarityX offers two testing options with our pharmacogenetic testing:

  • Mindwell test: This focuses on treatments for mental health conditions that include but are not limited to depression, anxiety, ADHD, OCD, psychosis, mood disorders, and more.
  • Max Rx test: This covers 31 therapeutic areas to test how an individual may respond to more than 265 medications.

Both the Mindwell and Max Rx tests may help determine how you will react to Seroquel and Zyprexa. This could help you and your healthcare provider make more informed decisions about your treatment plan. Click here to learn more.

1Sandoiu, A. (2017). Antipsychotics: Do they do more harm than good? Medical News Today. Retrieved September 6, 2022, from

U.S. Department of Health and Human Services. (n.d.). Fact sheet: First episode psychosis. National Institute of Mental Health. Retrieved September 6, 2022, from





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