1 What is Pentazine?

Brand: Pentazine, Phenergan, Phenadoz, Phen- Tuss, Promethegan

Generic: Promethazine

Pentazine is an antihistamine under phenothiazine group of drugs, used to treat symptoms of allergic reactions. This medication blocks histamine, a natural chemical produced by your body during allergic reactions, to relieve itching, rashes, runny nose, sneezing and other symptoms of allergies.

Pentazine also acts on the brain and affects other body chemicals (i.e. acetylcholine) to reduce pain and nausea. It is also used to induce sleep or as a sedative agent because it causes drowsiness.


Read your medication guide and follow your prescription label at all times.

  • Take Pentazine by mouth/orally before or after meals, 2- 4 times a day depending on the doctor’s prescription.
  • To treat motion sickness or nausea, take your first dose at least 30 minutes- 1 hour before traveling.
  • To treat allergic reactions, take Pentazine once a day during the sleeping hour to prevent drowsiness at daytime.
  • If Pentazine is used as sedative before surgery, take it at night time prior or just before the surgical procedure per doctor’s order.
  • Use a standard medicine cup/ spoon (not household spoon) to obtain the accurate amount for each dose if you are using the liquid form.
  • The dosage depends on your medical condition, weight or treatment response. Do not adjust your dose without your doctor’s recommendation.
  • Avoid alcohol intake and do not engage in activities that require mental alertness (i.e. driving, operating machinery) because Pentazine can cause drowsiness/ dizziness and blurring of vision.
  • Avoid overexposure to sunlight or tanning booths and wear protective clothes when you are outdoors because Pentazine can make you oversensitive to sunlight.
  • Continue taking Pentazine on a regular schedule (at the same time of the day). Do not stop taking Pentazine abruptly without consulting your doctor.
  • Do not give this to children less than 2 years old to prevent breathing problem such as slow or shallow breathing.

Inform your doctor immediately if your condition aggravates or does not improve.

Take your missed dose as soon as possible. However, make sure that the time interval between the missed and the next dose is not too close. Otherwise, stick with the regular schedule and leave out the missed dose. Do not double dose to cover up a missed dose. Record your missed doses and inform your doctor immediately if you missed several doses.


Pentazine may interact with:

  • Topical antihistamine (i.e. diphenhydramine ointment)
  • Metoclopramide
  • Sleeping pills
  • Alprazolam, diazepam, zolpidem and other anti- anxiety drugs
  • Muscle relaxants and
  • Narcotic pain relievers (i.e. codeine)

Some drugs may either lessen the beneficial effects or worsen the side effects of Pentazine. Likewise, Pentazine may make some drugs less efficient or intensify their side effects.

Make sure to inform your doctor about all other drugs you are currently taking or using (prescribed and non-prescribed medications including vitamins, minerals, and herbal products) to check for possible drug interaction with Pentazine.

Never alter the doses of other medications while on Pentazine neither stop nor start any medicine without the doctor’s recommendation.

Side Effects:

There are no side effects known aside from a possible allergic reaction in people who have previous or unknown hypersensitivity to the drug.

Watch out for signs of allergic reactions such as:

  • Rash
  • Itching
  • Swelling


Before taking Pentazine, tell your health care provider if you have/are:

  • Any allergies to any substance, food or medication, particularly to Pentazine or to another phenothiazine (i.e. prochlorperazine)
  • Medical history or a present condition such as:
    • Breathing disorder (i.e. asthma, chronic obstructive pulmonary disease/ COPD)
    • Bone marrow depression and other immune system or blood disorder
    • Glaucoma
    • Heart disease
    • High blood pressure or hypertension
    • Liver disease
    • Neuroleptic malignant syndrome, Reye’s syndrome, and another nervous system disease
    • Seizure
    • Increased activity of the thyroid or hyperthyroidism
    • Stomach or intestinal disorder
    • Trouble in urinating due to prostate enlargement
    • Diabetes
  • Pregnant, planning to get pregnant or currently breastfeeding a baby (It is not known if Pentazine can harm an unborn child or if it can pass through breast milk that may harm the nursing child. The risks and benefits of using this medication during pregnancy must be discussed well with your doctor.)
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