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Phenergan Injection

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Generic Name: Promethazine hydrochloride
Product Name: Phenergan Injection


Phenergan is an antihistamine used in the treatment of allergies; to stop nausea and vomiting; and for sedation and premedication.


Phenergan (promethazine) is derived from a group of medicines called phenothiazines, however, it is also part of the family of sedating antihistamines.

Histamine is a chemical in the body that causes the symptoms of an allergic reaction. These can include inflammation of the skin, airways or tissues, rashes, itching of the skin, eyes or nose, nasal congestion and narrowing of the airways. Promethazine blocks the binding of histamine to receptors in many areas of the body and thereby prevents the actions of histamine. This helps prevent and relieve the typical symptoms of an allergic reaction. Histamine may be released from and act in a small (localised) area of the body e.g. the nose. Alternatively, histamine can result in a serious or complete body reaction e.g. anaphylactic reaction. Promethazine is useful for the prevention or relief of localised or less serious allergies such as hay fever or itchy rash in addition to serious allergic reactions such as anaphylaxis.

Promethazine blocks histamine receptors in an area of the brain called the vomiting centre. It also acts to block other receptors in the vomiting centre (serotonin receptors). Therefore promethazine prevents the vomiting centre from sending the nerve messages to the stomach that would normally result in vomiting. Promethazine also acts on receptors in the gut (muscarinic receptors) to decrease the amount of fluid secreted from the lining of the gut and decrease the actions of the gut muscles. This further aids the treatment or prevention of nausea and vomiting.

Promethazine is known as a sedating antihistamine as it enters the brain in significant quantities and causes drowsiness. As a result it is commonly used for the short-term treatment of sleep disturbances and to provide sedation prior to minor procedures or surgery.

Dose advice

Dosage varies according to the condition being treated and the individual response to the dose

Allergic Disorders:

  • Adults: 25-75mg as a single dose at night, or 10-20mg 2-3 times daily
  • Children 6 to 12 years: 10-25mg as a single dose at night, or 10mg 2-3 times daily
  • Children 2 to 5 years: 5-15mg as a single dose at night, or 5mg 2-3 times daily


  • Adults: 25 to 75mg as a single dose at night
  • Children 6 to 12 years: 10-25mg as a single dose at night
  • Children 2 to 5 years: 5-15mg as a single dose at night

Travel sickness:

To be taken the night before travel and repeated every 6-8 hours on the following day as required

  • Adults: 25mg as a single dose
  • Children 6 to 12 years: 10mg as a single dose
  • Children 2 to 5 years: 5mg as a single dose

Nausea and Vomiting:

  • Adults: 25mg every 4-6 hours to a maximum daily dose of 100mg
  • Children 6 to 12 years: 10mg every 4-6 hours to a maximum daily dose of 25mg
  • Children 2 to 5 years: 5mg every 4-6 hours to a maximum daily dose of 15mg



Common side effects

When taking Phenergan, you may experience some of the following:

  • Dry mouth
  • Loss of appetite
  • Nausea
  • Vomiting
  • Diarrhoea
  • Constipation
  • Sedation
  • Restlessness
  • Dizziness
  • Fatigue
  • Uncoordination
  • Blurred vision

Uncommon side effects

Tell your doctor if any of the following side effects affect you:

  • Increased/decreased heart rate
  • Feeling of faintness
  • Increased sensitivity to the sun
  • Rash
  • Swelling
  • Ringing in the ears
  • Yellowness of the eyes or skin
  • Nervousness
  • Insomnia
  • Abnormal movements of the hands, legs, face, neck and tongue, e.g. tremor, twitching, rigidity (extrapyramidal effects)
  • Rhythmical involuntary movement of the tongue, face, mouth and jaw, which may sometimes be accompanied by involuntary movements of the arms and legs (tardive dyskinesia)

For further information talk to your doctor.

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Posted On: 22 July, 2003
Modified On: 22 October, 2015


Created by: myVMC