Thiethylperazine (Intramuscular, Oral, Rectal)

Thiethylperazine is a phenothiazine and CNS depressant which relieves nausea and vomiting associated with chemotherapy, radiation therapy and anesthesia.


Thiethylperazine is a phenothiazine which works to relieve nausea and vomiting. It is particularly effective in treating nausea and vomiting associated with anesthesia, radiation therapy, emetic cancer chemotherapy agents and other toxins. It is not designed for use in people who experience nausea and vomiting as a result of motion sickness or vertigo.

This drug is only available with a doctor's prescription and is available in tablet form to be taken orally, a solution to be injected into the muscle, and suppository form to be taken rectally. In the US, the drug is known under the brand name Torecan.

Condition(s) treated?

  • Nausea
  • Vomiting

Type of medicine?

  • Phenothiazine

Side Effects

There are a wide variety of side effects associated with thiethylperazine, some of which are serious and require urgent medical care, and some of which are minor. It's important to familiarize yourself with all side effects so that in the event of experiencing dangerous ones you can seek care as quickly as possible.

The following symptoms should be mentioned to your doctor as soon as possible:

  • Abdominal or stomach pains
  • Swelling of hands, arms or face
  • Joint and muscle aches
  • Muscles spasms
  • Convulsions or seizures
  • Shuffling walk
  • Difficulty swallowing or speak
  • Rapid heartbeat
  • Blurred vision, color changes or poor night vision
  • Loss of balance control
  • Shuffling walk
  • Fever and chills
  • Smacking or puckering of lips
  • Puffing of cheeks
  • Rapid, worm-like movements of tongue
  • Tic-like, twitching movements
  • Uncontrolled chewing movements
  • Uncontrolled movements or arms or legs
  • Mask-like face (difficulty moving face)
  • Nausea, vomiting or diarrhea
  • Nosebleeds
  • Yellow skin or eyes
  • Sore throat with fever
  • Unusual bruising or bleeding
  • Confusion
  • Excitement, nervousness, restlessness or irritability
  • Abnormal lethargy, fatigue or weakness

The following side effects are relatively minor and do not require urgent medical attention. If they become particularly persistent or bothersome, you may want to discuss them with your doctor:

  • Dizziness
  • Drowsiness
  • Lightheadedness or dizziness when getting up from sitting or lying down
  • Fainting
  • Fever
  • Headache
  • Ringing or buzzing in ears
  • Skin rash
  • Dryness of mouth, nose and throat
  • Constipation

If you notice any other side effects not listed here, refer them to your doctor. You could also report them to the FDA.

Overdose of thiethylperazine

As with any drug, an overdose of thiethylperazine could be incredibly dangerous. If you believe you've taken more thiethylperazine than you should have done, seek urgent care even if you feel well. The following symptoms are signs of thiethylperazine overdose:

  • Severe confusion
  • Serve convulsions or seizures
  • Spasms in neck and face
  • Hyperextension of neck and trunk
  • Severe dizziness or drowsiness
  • Loss of consciousness
  • Severe dry mouth
  • Inability to move eyes
  • Labored breathing
  • Stuffy nose


Adults and children over the age of 12 usually require 10 mg of thiethylperazine, 1 to 3 times each day. However, this may vary depending on your medical history and the severity of your nausea and vomiting symptoms. The drug can be taken orally, rectally or via intramuscular injection.

Oral route administration

Thiethylperazine tablets should be taken with food or with an 8-ounce glass of water or milk. This will help to prevent stomach irritation. If you miss a dose, take it as soon as you remember unless it is almost time for the next dose, in which case simply skip the missed dose and maintain your original dosing schedule. Do not double dose on thiethylperazine to make up for a missed dose.

Rectal route administration

Thiethylperazine suppositories are supplied in foil wrappers which should be removed before insertion. Moisten the suppository with cold water, then insert it reasonably high into the rectum using your finger. Laying down on your side might help to make the insertion process easier. If suppositories are very soft and difficult to insert, you can place them in the fridge for 30 minutes first, or run them under cold water until they firm up. Always wash hands with warm, soapy water after inserting a suppository. If you have missed a dose of thiethylperazine, take it as soon as you remember unless it is almost time for the next dose. In these instances, simply skip the missed dose and take the next one at the usual time. Never insert more than one thiethylperazine suppository at one time.

Intramuscular route

Thiethylperazine is usually administered via intramuscular injection when it is needed to relieve nausea and vomiting associated with surgery and anesthesia. It is therefore usually administered by a doctor, nurse or other trained healthcare professional shortly before anesthesia is terminated. If you are to administer thiethylperazine injections yourself at home, follow the advice given to you by your healthcare provider.


Central nervous system (CNS) depressants

Thiethylperazine is a CNS depressant, and if administered concurrently with other CNS depressants these effects could be heightened. CNS depressants can lead to breathing difficulties, blurred vision, impaired thinking, slowed reflexes, uncoordinated movement and, in the worst instances, unconsciousness and coma.

Examples of other CNS depressants include:

  • Barbiturates, often used to treat mild anxiety and sleep disorders, such as:
    • Amobarbital (Amytal)
    • Mephobarbital (Mebaral)
    • Pentobarbitalsodium (Nembutal)
  • Benzopdiazepines, often used to treat acute anxiety, stress and panic attacks, such as:
    • Alprazolam (Xanax)
    • Chlordiazepoxide HCI (Librium)
    • Diazepam (Valium)
  • Non-benzodiazepine sleep medications, such as
    • Eszopiclone (Lunesta)
    • Zalepon (Sonata)
    • Zolpidem (Ambien)

Make sure your doctor is aware of all CNS depressants you are taking. They may adjust your dosages or instruct you to take them at different times to minimize the potential risk of harmful CNS depression during thiethylperazine therapy.

Alcohol is also a CNS depressant, and patients taking thiethylperazine should use great caution when consuming alcohol with the drug. It is usually safest to avoid alcohol completely during thiethylperazine therapy, but at the very least you should have no more than one or two drinks while taking the medicine.

Contraindicated interactions

The only medicine which is completely contraindicated for use alongside thiethylperazine is saquinavir (Invirase), which is a drug used to treat HIV infection. Individuals who are already taking saquinavir are likely to be prescribed alternative therapies to treat nausea and vomiting while avoiding harmful interactions.

Interactions which may require dosage adjustments

The following medicines are known to interact with thiethylperazine, but they may still be prescribed if both medicines are absolutely necessary. Doses or dosage schedules may be adjusted to minimize interaction:

  • Alfentanil
  • Bromazepam
  • Buprenorphine
  • Butorphanol
  • Codeine
  • Dihydrocodeine
  • Donepezil
  • Doxylamine
  • Fentanyl
  • Flibanserin
  • Gatifloxacin
  • Hydrocodone
  • Hydromorphone
  • Ibutilide
  • Isradipine
  • Levorphanol
  • Meperidine
  • Methadone
  • Metrizamide
  • Morphine
  • Morphine Sulfate Liposome
  • Nalbuphine
  • Octreotide
  • Oxycodone
  • Oxymorphone
  • Pentamidine
  • Pentazocine
  • Periciazine
  • Procarbazine
  • Remifentanil
  • Sufentanil
  • Tapentadol
  • Tramadol

The following drugs are known to interact with thiethylperazine and may increase the risk of certain side effects. However, they may still be prescribed with adjusted dosages if the benefits of both drugs outweigh the risk of side effects:

  • Aminolevulinic Acid
  • Belladonna
  • Belladonna Alkaloids
  • Betel Nut
  • Evening Primrose
  • Phenylalanine

Interactions with other medical problems

Some pre-existing medical problems might interact with thiethylperazine and increase the risk or side effects or affect the way the drug behaves. Make sure your doctor is aware of your entire medical history, including all of the conditions you suffer from now and have done in the past.

Thiethylperazine could cause lung secretions to thicken and make them difficult to cough up in people with asthma or with other lung diseases.

People with a blood disease, heart disease or blood vessel disease may see complications of their condition when taking thiethylperazine.

Thiethylperazine can make urinary problems worse in people who are already suffering from an enlarged prostate or who have difficult urination.

In people with glaucoma, thiethylperazine might increase inner eye pressure and cause complications.

People with liver disease are at an increased risk of side effects when taking thiethylperazine because the drug could accumulate in the body which might enhance its effects.

Patients with Parkinson's disease or seizure disorders are at a higher risk of seizures or uncontrolled movements when taking thiethylperazine than those without these conditions.


Risk of hypersensitive or allergic reaction

The injected form of the drug contains sodium metabisulfite which can cause allergic reactions, anaphylactic reactions or asthmatic episodes in some people. The risk of these reactions are relatively low for the general population, but asthmatic individuals are at a higher risk of an adverse reaction than non-asthmatic people. The drug is also unsuitable for patients who have had a hypersensitive reaction to phenothiazines in the past.

Risk of CNS depression

Thiethylperazine is contraindicated in individuals with severe central nervous (CNS) system depression and in comatose states because it can cause further CNS depression.

If thiethylperazine is injected to control postoperative nausea and vomiting in those who have had surgery, it poses the risk of causing CNS depression during anesthesia recovery. This may lead to complications.

CNS depressants like thiethylperazine can cause drowsiness and blurred vision. Patients should therefore take care when considering driving or operating machinery when using the medication. Only do so if you know how the drug affects you and you feel completely confident that it is safe to do so. The drowsiness associated with thiethylperazine often dissipates after the first few days of taking the medicine as the body adjusts, so you may have to avoid driving or operating machinery for a short period only.

Potential risk of breast cancer

Thiethylperazine, like all phenothiazine drugs, can lead to an elevation of prolactin levels. Prolactin is a hormone produced by the body which around one-third of breast cancers are dependent on. Elevated prolactin levels may not be a problem for most people, but it might pose an increased risk of breast cancer in individuals who have had it in the past. The risk is very low, and is only likely if the individual takes thiethylperazine for a long period of time. Nonetheless, a history of breast cancer is something that doctors should always know about when they are considering the prescription of thiethylperazine.

Use of thiethylperazine during pregnancy and breastfeeding

Thiethylperazine has not been assigned a pregnancy category by the FDA, but the manufacturer of the drug has stated that it is contraindicated during pregnancy.

There have not been enough studies performed on nursing women to understand whether thiethylperazine poses a risk to nursing infants. It isn't clear whether the drug is excreted in human breast milk, but since many are we can assume that thiethylperazine is too. What effects the drug might have on a nursing baby is unknown. For this reason, women who are taking thiethylperazine are advised not to breastfeed.

Enhanced effects in elderly patients

Elderly patients tend to be more sensitive to the effects of phenothiazines such as thiethylperazine. This means that they might experience more drowsiness, dizziness, nervousness and other side effects than younger adults when taking the medicine. Doctors may reduce the dosage of thiethylperazine to reduce these enhanced effects.


Thiethylperazine should be stored in a room temperature environment away from direct light, heat or moisture. It should not be frozen. Store it in a closed container, preferably with a childproof safety cap.

If using thiethylperazine suppositories, you can keep them in the fridge prior to insertion for up to 30 minutes in order to ensure that they are cool and firm enough for easier insertion. However, they should not be stored in the fridge permanently.

Keep thiethylperazine away from children and pets by keeping it up and away from the ground so that it is not within easy reach.

If you have leftover thiethylperazine medication that you no longer need, do not keep hold of it. Instead, ask your healthcare provider how to dispose of it properly. Never use expired medicine.


Thiethylperazine is a phenothiazine used to treat nausea and vomiting. It is often prescribed to relieve these symptoms in patients undergoing chemotherapy, radiation therapy, anesthesia and other treatments which involve toxic ingredients. It works on the central nervous system (CNS). The drug is available in tablet form for oral use, suppository form for rectal use, or solution form for intramuscular injection, although the latter is usually reserved for treating postoperative nausea and vomiting associated with anesthesia.

Since thiethylperazine is a CNS depressant, the most common side effects associated with the drug are drowsiness and dizziness. These do not usually require medical attention, but if they become very severe and the patient also experiences confusion, labored breathing or abnormal bodily movements, urgent medical care may be necessary.

The typical dosage of thiethylperazine is 10 mg taken 1 to 3 times each day. The tablet form of the drug should be taken with food or a full glass of water or milk to reduce stomach irritation. Children under the age of 12 are rarely prescribed the drug as the safety and efficacy of thiethylperazine has not been established in this age group. The drug is also contraindicated for pregnant women and is not recommended while breastfeeding.

Thiethylperazine should be used with caution alongside other CNS depressants, such as barbiturates, benzodiazepines, and non-benzodiazepine sleep medications, because the combination of these drugs could lead to respiratory depression and other serious side effects of CNS depression. Alcohol should be avoided when taking thiethylperazine for the same reason.

The drug poses a risk of seizures or convulsions and may not be suitable for people with Parkinson's disease or seizure disorders because they will be at a higher risk of convulsions. It should also be used with caution in people with asthma or lung diseases, blood, heart or blood vessel diseases, prostate or urinary problems, glaucoma, and liver disease. In all of these instances, thiethylperazine could increase the risk of side effects, make the pre-existing health problem worse or cause other health complications.

Last Reviewed:
December 24, 2017
Last Updated:
April 05, 2018
Content Source: