Monday, May 27, 2024
Homebreast cancerHaldol (haloperidol) vs. Zyprexa (olanzapine): Antipsychotic Side Effects

Haldol (haloperidol) vs. Zyprexa (olanzapine): Antipsychotic Side Effects

Haldol (haloperidol) vs. Zyprexa (olanzapine): What’s the difference?

  • Haloperidol and olanzapine are different types of antipsychotic medications used to treat schizophrenia
  • Haloperidol is also used to treat acute psychosis and for tics and vocal utterances of Tourette's syndrome.
  • Olanzapine is also used to treat acute manic episodes associated with bipolar I disorder and some types of depression.
  • A brand name for haloperidol is Haldol.
  • Brand names for olanzapine include Zyprexa, Zyprexa Zydis, and Zyprexa Relprevv.
  • Side effects of haloperidol and olanzapine that are similar include extrapyramidal effects (sudden, often jerky, involuntary motions of the head, neck, arms, body, or eyes; muscle stiffness, restlessness, Parkinsonism), dizziness, tiredness/drowsiness, weight gain, insomnia, dry mouth, constipation, and dizziness on standing.
  • Side effects of haloperidol that are different from olanzapine include hyperactivity, nausea, sedation, erectile dysfunction, menstrual irregularities, swelling of breast tissue in males (gynecomastia), and vomiting.
  • Side effects of olanzapine that are different from haloperidol include an inability to sit still (akathisia) and tremor.
  • Do not stop using haloperidol suddenly, or you could have unpleasant withdrawal symptoms.

What is haloperidol? What is olanzapine?

Haloperidol is an antipsychotic medication used for treating schizophrenia, acute psychosis, and to control tics and vocal utterances of Tourette's syndrome. Haloperidol interferes with the effects of neurotransmitters in the brain. Haloperidol blocks receptors for the neurotransmitters dopamine and serotonin type 2 so the nerves are not "activated" by these neurotransmitters.

Olanzapine is an atypical antipsychotic used to treat schizophrenia, acute manic episodes associated with bipolar I disorder, and some types of depression. The exact mechanism of action of olanzapine is unknown. It may work by blocking receptors for several neurotransmitters in the brain. It binds to alpha-1, dopamine, histamine H-1, muscarinic, and serotonin type 2 (5-HT2) receptors.

What are the side effects of haloperidol and olanzapine?


The most common side effects associated with Haldol are:

  • extrapyramidal effects (sudden, often jerky, involuntary motions of the head, neck, arms, body, or eyes, muscle stiffness, akathisia, Parkinsonism),
  • dizziness,
  • hyperactivity,
  • tiredness, and
  • nausea.

Other important side effects are:

Haldol may cause a condition called "orthostatic hypotension" during the early phase of treatment (first week or two). Orthostatic hypotension causes patients to become dizzy upon arising from a lying or sitting position because of a drop in blood pressure.

Haldol also may cause abnormal heart beats, sudden death, seizures, decreases in red and white blood cells, and withdrawal symptoms.

Elderly patients with dementia-related psychosis and treated with antipsychotic drugs such as Haldol are at an increased risk of early death.



  • Elderly patients with dementia related psychosis treated with antipsychotics are at an increased risk of death.
  • When using olanzapine and fluoxetine in combination, also refer to the boxed warning section of the package insert for Symbyax.

Common side effects

Common side effects seen with olanzapine are:

Several disorders of movement also may occur with olanzapine, for example, extrapyramidal effects (sudden, often jerky, involuntary motions of the head, neck, arms, body, or eyes). Tardive dyskinesia (involuntary movements of the mouth, tongue, jaw, or eyelids) also may occur in 1 in 100 patients receiving olanzapine. Some cases can be irreversible. The likelihood of developing tardive dyskinesia increases with prolonged treatment.

There may be an increased risk of elevated blood sugar levels and diabetes with olanzapine as well as the other antipsychotic medications in its class. Patients should be tested during treatment for elevated blood sugar. Additionally, persons with risk factors for diabetes, including obesity or a family history of diabetes, should have their fasting levels of blood sugar tested before starting treatment and periodically throughout treatment to detect the onset of diabetes. Any patient developing symptoms that suggest diabetes during treatment should be tested for diabetes.

Patients may develop severe sedation, coma, and or delirium after an injection of extended release olanzapine. Patients must be examined for 3 hours after receiving an injection.

Olanzapine may increase prolactin levels. Increased prolactin levels may manifest as abnormal menstruation, sexual dysfunction, and breast enlargement.

Latest Mental Health News

Trending on MedicineNet

What is the dosage for haloperidol vs. olanzapine?


  • The recommended oral dose for schizophrenia is 0.5-5 mg two or three times daily up to a maximum dose of 30 mg daily. The lactate solution dose is 2-5 mg every 4-8 hours as needed by intramuscular injection. The lactate solution may also be administered by intravenous injection at 1-2 mg every 2-4 hours and titrated to effect. The maximum single injection dose is 50 mg and the maximum daily dose is 500 mg daily. The dose for the decanoate solution is 10-20 times the daily oral dose once monthly by intramuscular injection. The decanoate solution should not be administered intravenously.
  • The recommended dose for treating Tourette's syndrome is 0.5-5 mg orally two or three times daily.


  • The usual oral dose of olanzapine for treating schizophrenia is 10-20 mg once daily. Therapy is initiated with 5-10 mg/day, and the dose may be increased by 5 mg a day at weekly intervals. The maximum dose is 20 mg daily. The recommended dose of extended release injection is 150-405 mg every 2 or 4 weeks.
  • Treatment of bipolar disorder usually is initiated with oral doses of 10-15 mg once daily. The dose may be increased by 5 mg daily at 24 hour intervals. The maximum dose is 20 mg daily.
  • The usual dose for treating agitation due to schizophrenia or bipolar disorder is 10 mg administered by intramuscular injection (immediate release). Additional 10 mg doses may be administered, but the efficacy of total doses greater than 30 mg daily have not been adequately evaluated.
  • The recommended treatment for resistant depression is 5-20 mg of olanzapine combined with 20-50 mg of fluoxetine once daily in the evening while the recommended treatment for depression associated with bipolar disorder is 5-12.5 mg olanzapine combined with 20-50 mg fluoxetine once daily in the evening.


Laughter feels good because…
See Answer

What drugs interact with haloperidol and olanzapine?


Haldol causes sedation, and sedation may be greater if Haldol is taken with alcohol and other drugs that can cause sedation such as the benzodiazepine class of anti-anxiety drugs for example:

The narcotic class of pain medications and its derivatives for example:

The tricyclic class of antidepressants for example:

Some antihistamines for example:

Certain antihypertensive medications for example:

Carbamazepine (Tegretol) may increase the elimination of Haldol, rendering the Haldol less effective. Rifampin (Rifadin) may decrease the elimination of Haldol, increasing the risk of side effects from Haldol.


  • Carbamazepine (Tegretol) can reduce blood concentrations of olanzapine, possibly necessitating higher doses of olanzapine. Other drugs that may also reduce blood levels of olanzapine are omeprazole (Prilosec) and rifampin.
  • Smoking may reduce blood concentrations of olanzapine.
  • Ciprofloxacin (Cipro), diltiazem (Cardizem, Dilacor, Tiazac), erythromycin, and fluvoxamine (Luvox) may have the opposite effect, that is, they may increase blood levels of olanzapine, and the dose of olanzapine may need to be reduced.
  • Olanzapine can cause orthostatic hypotension, a drop in blood pressure upon standing up that may cause dizziness or even fainting. Taking olanzapine with either diazepam (Valium), other related benzodiazepines or alcohol can exaggerate the orthostatic hypotension caused by olanzapine.

Subscribe to MedicineNet’s Depression Newsletter

By clicking “Submit,” I agree to the MedicineNet Terms and Conditions and Privacy Policy. I also agree to receive emails from MedicineNet and I understand that I may opt out of MedicineNet subscriptions at any time.

Are haloperidol and olanzapine safe to use while pregnant or breastfeeding?


  • Neonates exposed to antipsychotics during the 3rd trimester of pregnancy may develop withdrawal symptoms and extrapyramidal symptoms.
  • Haldol is secreted into breast milk. It should not be used while breast feeding.


  • There are no adequate studies of olanzapine in pregnant women. Olanzapine should only be administered to pregnant women if the benefits justify the unknown risks.
  • Olanzapine is excreted into breast milk. Therefore, it is recommended that olanzapine not be used by nursing mothers.

Most Popular