Phenergan is a part of a group of drugs called “promethazines” – a phenothiazine derivative with antidopaminergic, antihistamine, and anticholinergic properties. The FDA-approved drug is a direct antagonist at the mesolimbic dopamine receptors and alpha-adrenergic receptors, allowing for antihistamine effects as an H1-receptor blocker.

Phenergan is typically used to treat nausea, vomiting, motion sickness, and allergic reactions such as rashes, itching, and runny noses. It may also be used for sedation or to help with cold symptoms. The drug is typically taken orally two to four times per day. Some injectable doses may also be available. The doses are usually prescribed within a certain period before the desired or anticipated reaction, which may vary based on its use.

Phenergan Precautions and Warnings

Patients should avoid taking Phenergan if they have narrow-angle glaucoma, prostatic hypertrophy, stenosing peptic ulcer, pylori duodenal obstruction, or a bladder-neck obstruction. This is because of the drug’s anticholinergic properties. Phenergan should also be used with caution for patients who have cardiovascular disease or impaired liver function.

Phenergan suppositories increase risks of CNS depression, potentially impairing mental and physical abilities required for tasks such as driving or operating machinery. Use with other CNS depressants may amplify this impairment. Additionally, respiratory depression, lowered seizure threshold, bone marrow depression, and Neuroleptic Malignant Syndrome (NMS) are associated risks.

Patients with compromised respiratory function should avoid Phenergan use, and caution is warranted in those with seizure disorders or bone marrow depression. NMS, though rare, requires immediate discontinuation of Phenergan and other implicated drugs, along with intensive symptomatic treatment. Careful consideration is needed before reintroducing Phenergan due to reported recurrences of NMS with phenothiazines.

Ages 65 and Older

Clinical studies of promethazine formulations needed more representation of subjects aged 65 and over, preventing the determination of differential responses compared to younger individuals. However, reported clinical experiences did not reveal notable response variations between elderly and younger patients.

To mitigate potential risks associated with decreased hepatic, renal, or cardiac function and concomitant diseases or drug therapies, cautious dose selection is recommended for elderly patients. Starting with lower doses of Phenergan suppositories is advised due to the risk of confusion and oversedation in the elderly, necessitating close monitoring for adverse effects.

Pediatric Patients and Children

Phenergan should not be used for pediatric patients less than two years old. This may increase the risk of fatal respiratory depression. Cases of this, including some fatalities, have been reported. For pediatric patients of this age group, it is recommended only to administer the lowest effective dose to avoid any other respiratory depressant effect. The use of Phenergan also puts this group at increased risk for apnea, Reye’s Syndrome, and other hepatic diseases.

No evidence supports the safety or efficacy of cough-and-cold products in children under six. Only use these products for cold symptoms in young children if explicitly directed by a doctor. Additionally, certain products like long-acting tablets/capsules are unsuitable for children under 12.

Fertility and Pregnancy

Studies have not yet been done to study Phenergan’s effect on fertility. Those who are pregnant are urged to remain cautious. During rat-feeding studies, teratogenic effects were not observed at doses of 6.25 and 12.5 mg/kg of promethazine (approximately 2.1 to 4.2 times the maximum recommended daily dose for a 50-kg subject). However, higher doses of 25 mg/kg intraperitoneally resulted in fetal mortality.

No specific studies were done on the drug’s effects on parturition, lactation, and neonatal development.  Preliminary findings in rats showed no significant impact.

Phenergan should be used during pregnancy only when the potential benefits outweigh the possible risks to the fetus. Administering Phenergan to a pregnant woman within two weeks of delivery may also inhibit platelet aggregation in the newborn.

During labor and delivery, promethazine HCl can be used alone or with narcotic analgesics without significantly affecting labor duration or the need for intervention in the newborn. The impact on the newborn’s future growth and development is still unknown. It is uncertain if promethazine HCl is excreted in human milk. I think caution is advised because of the potential for adverse reactions in nursing infants.

Phenergan Side Effects

There are many side effects to be aware of when taking Phenergan.

Common Side Effects

The most common side effects include:

  • Fatigue during the day
  • Bad dreams
  • Dizziness or unsteadiness
  • Difficulty concentrating
  • Headaches
  • High skin sensitivity to sunlight

Severe Side Effects

Adults over age 65 are at increased risk of experiencing more severe side effects. They should talk with a doctor if they are experiencing:

  • Confusion
  • Dry mouth
  • Cloudy vision
  • Trouble urinating
Uncommon Severe Side Effects

Other serious, less common side effects include:

  • Yellowing whites of the eyes
  • Increased bruising and bleeding
  • Muscle stiffness
  • Shaking
  • Unusual movement in the face or tongue

Phenergan Drug Interactions

Phenergan may have harmful interactions with some central nervous system depressants, anticholinergic medications, neurological medications, cardiovascular medications, and gastrointestinal medications.

Medical attention should be sought immediately if symptoms such as pale or blue lips, fingernails, skin, difficulty breathing, irregular breathing patterns, or shortness of breath are experienced, as these may indicate respiratory depression.

Talk to a doctor and discontinue medication if directed by a healthcare provider upon encountering symptoms such as muscle stiffness, fever, rapid or complex breathing, seizures, increased heart rate, excessive sweating, loss of bladder control, ashen skin, or feelings of fatigue or weakness, as these could signal a serious condition known as neuroleptic malignant syndrome. Also, talk to a doctor before consuming alcohol or other central nervous system depressants alongside the medication.

Some specific types of medications to avoid while on Phenergan include:

  • Other sedatives
  • Narcotics
  • Sleeping medication
  • Muscle relaxers
  • Seizure medications
  • Antidepressants
  • Anxiety medication
  • Lithium
  • Atropine
  • Benztropine
  • Dimenhydrinate
  • Methscopolamine
  • Scopolamine
  • Blood pressure medications
  • Blood thinners (such as Eliquis or Xarelto)
  • Bronchodilators (such as Anoro)
  • Bladder medications
  • MAO inhibitors
  • Parkinson’s disease medications (such as Neupro)
  • Restless leg syndrome medications
  • Pituitary gland tumors medications
  • Stomach ulcer medications
  • Irritable bowel syndrome medications

Phenergan Strengths and Dosages

The typical recommended doses are as follows:

 Allergy SymptomsMotion SicknessNausea and VomitingSedationPain or Anxiety Control for Surgery
Teenagers and Adults12.5 mg before meals and at bedtime or 25 mg at bedtime as needed25 mg twice per day, with the initial dose taken 30 to 60 minutes before traveling


Dose may be repeated 8 to 12 hours later if necessary

25 mg initially, increased to 12.5 to 25 mg every 4 to 6 hours as needed25 to 50 mg as needed50 mg the night before surgery, followed by 25 to 50 mg after surgery
Children Age 2 and OlderDetermined by weight and/or size (typically between 6.25 to 12.5 mg three times per day, or 25 mg at bedtime as needed)Determined by weight and/or size. (typically between 12.5 and 25 mg 30 to 60 minutes before traveling)


The dose may be repeated 8 to 12 hours later if necessary

Determined by weight and size (typically 0.5 mg per pound of body weight, or 12.5 to 25 mg every 4 to 6 hours as needed).Determined by weight and size (typically 12.5 to 25 mg)Determined by weight and size (typically 0.5 mg per pound of body weight, or 12.5 to 25 mg before or after surgery).
Children Under Age 2Consult a doctor for appropriate dosageConsult a doctor for appropriate dosageConsult a doctor for appropriate dosageConsult a doctor for proper dosageConsult a doctor for appropriate dosage.


Individuals should talk with a doctor before taking any medication. The oral medication can be taken with food, a glass of water, or a glass of milk to lessen stomach irritation.

Frequently Asked Questions About Phenegran

Your healthcare professional should answer all your questions, as they will be able to evaluate the details of your lifestyle.

Does Phenegran make you sleepy?

Phenergan does cause sleepiness. One of its many uses is as a sedative, typically for those undergoing surgical procedures. Taking too much of the medication can also increase these otherwise mild effects.

Is Phenegran safe to use during pregnancy?

Many studies have not yet proven whether Phenegran is harmful during pregnancy. Use with caution and only if instructed by a medical professional. It may sometimes be prescribed for C-section surgeries or to reduce the effects of nausea during pregnancy. Some experts suggest stopping taking the drug two weeks before the delivery date as it may cause irritability or excitement in the mother.

How long does it take for Phenegran to start working?

Promethazine acts quickly. Usually, symptoms can be improved within 20 minutes of taking the medication. The effects of promethazine generally persist for 4-6 hours but may extend up to 12 hours.

What is the cost of Phenergan in America?

A Phenergan injectable solution costs around $98 for a supply of 25 milliliters before coupons or coverage options. This may vary depending on the pharmacy.

IMPORTANT NOTE: The information provided here is for educational purposes only and is not intended to serve as medical advice, diagnosis, or treatment recommendations. It should not be taken as an endorsement of any specific medication or treatment. Individual health conditions and responses to treatment can vary greatly; therefore, this information should not be seen as a guarantee of safety, suitability, or effectiveness for any particular individual. Always consult with a healthcare professional for personalized medical advice and before making any decisions regarding your health or treatment plans.

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