In what patients should you avoid Phenergan?

October 12, 2025 •

3 min read

The U.S. Food and Drug Administration (FDA) has issued a boxed warning for Phenergan (promethazine), explicitly prohibiting its use in pediatric patients younger than 2 years of age because of the risk of potentially fatal respiratory depression. This caution extends to other vulnerable populations and individuals with specific health conditions where the medication's risks outweigh its benefits.

Quick Summary

Promethazine is contraindicated in children under 2 and patients in a comatose state due to respiratory depression risks. It should be avoided or used with caution in the elderly, those with compromised breathing, glaucoma, seizures, and other specific medical conditions.

Key Points

Pediatric Risk: Promethazine is contraindicated in children younger than 2 years due to the risk of fatal respiratory depression.
Elderly Sensitivity: Avoid in older adults due to increased risk of anticholinergic side effects, sedation, confusion, and falls.
Respiratory Compromise: Patients with asthma, COPD, or sleep apnea should not take Phenergan due to the risk of worsening respiratory function.
Seizure Potential: Promethazine lowers the seizure threshold and should be avoided in patients with a history of seizures.
Drug Interactions: Concomitant use with other CNS depressants, like alcohol or narcotics, is dangerous and can cause amplified sedative effects.
Anticholinergic Concerns: Avoid in patients with conditions aggravated by anticholinergic effects, such as narrow-angle glaucoma and urinary obstruction.
Injection Risk: Parenteral (injection) use carries a risk of severe tissue injury, including gangrene, especially with improper administration.

Phenergan, also known as promethazine, is a first-generation antihistamine used to treat allergies, motion sickness, nausea, and can also act as a sedative for sleep or pre- and post-operative care. However, it carries significant risks and is not suitable for all individuals. Understanding these risks and contraindications is crucial for safe use.

The pediatric population

A critical warning for Phenergan involves young children. Due to the risk of potentially fatal respiratory depression, the FDA has issued a boxed warning against using promethazine in children younger than 2 years old. This risk exists regardless of the dose. While children aged 2 and older may use Phenergan, caution is still necessary. The lowest effective dose should be used, and it should not be given with other medications that depress the respiratory system. Some health authorities also recommend avoiding oral promethazine in children under 6 due to concerns about central nervous system and psychiatric side effects.

The geriatric population

Older adults are also at higher risk for adverse effects from Phenergan. It is listed in the American Geriatrics Society's Beers Criteria as potentially inappropriate for this population, mainly due to its strong anticholinergic effects. These effects can lead to issues like dry mouth, blurred vision, urinary retention, constipation, confusion, delirium, and an increased risk of falls in seniors. The slower metabolism in older adults can also lead to drug accumulation and increased toxicity. If used, a low starting dose is recommended.

Patients with compromised respiratory function

Because Phenergan can suppress breathing, it should be avoided in individuals with existing respiratory problems. This includes conditions like asthma, Chronic Obstructive Pulmonary Disease (COPD), and sleep apnea. Using Phenergan in these patients could dangerously worsen their breathing.

Patients with seizure disorders

Promethazine can lower the threshold for seizures, making individuals with a history of seizure disorders more susceptible to experiencing them. {Link: MedCentral medcentral.com}

Patients with specific medical conditions

Promethazine use requires caution or avoidance in individuals with certain medical conditions, including bone-marrow depression, narrow-angle glaucoma, urinary or gastric obstruction, impaired liver function, cardiovascular disease, or a history of Neuroleptic Malignant Syndrome (NMS).

Comparison of Promethazine Risks in Different Patient Groups

A comparison of promethazine risks across various patient populations can be found on {Link: MedCentral medcentral.com}

Interactions with other medications

Phenergan can increase the effects of other CNS depressants like alcohol, narcotics, tranquilizers, and sedatives, leading to increased sedation.

Consideration for pregnancy and breastfeeding

Promethazine is classified as Pregnancy Category C. Animal studies suggest potential harm at high doses. Using it near delivery could affect newborn platelet aggregation. It is unknown if promethazine passes into breast milk, and its sedative effects could impact a nursing infant. Safer alternatives are often preferred during pregnancy and breastfeeding.

Conclusion

While useful for certain conditions, Phenergan is not appropriate for everyone. Key contraindications include children under 2 and those with compromised breathing. Caution and often avoidance are necessary for the elderly and individuals with conditions like seizures, glaucoma, severe liver or cardiovascular disease. A thorough patient evaluation is essential before prescribing. For comprehensive prescribing details, consult authoritative sources such as {Link: DailyMed dailymed.nlm.nih.gov}.

Frequently Asked Questions

The FDA has placed a black box warning on Phenergan for children younger than 2 because it can cause severe and sometimes fatal respiratory depression (slowed or stopped breathing).

Generally, Phenergan should be avoided in elderly patients, particularly those over 65. They are more susceptible to side effects like confusion, excessive sedation, and an increased risk of falls due to the medication's strong anticholinergic properties.

No, Phenergan is contraindicated in patients with compromised respiratory function, including those with asthma, COPD, and sleep apnea, as it can worsen their breathing difficulties.

Phenergan has dangerous interactions with other CNS depressants, including alcohol, narcotics, sedatives, and tranquilizers. This combination can cause excessive drowsiness and slowed breathing.

Phenergan is a Pregnancy Category C drug, meaning there are no adequate human studies to confirm its safety. Use is only recommended if the potential benefits justify the potential risks, and safer alternatives may be preferred.

NMS is a rare but potentially fatal reaction characterized by high fever, muscle rigidity, and altered mental status. It has been reported in patients taking promethazine, either alone or with antipsychotic drugs, so anyone with a history of NMS should not use Phenergan.

Yes, the injection form of Phenergan carries a risk of severe tissue injury, including gangrene, regardless of the administration route. The preferred route for injection is deep intramuscular, while intravenous concentrations above 1 mg/mL, intra-arterial, and subcutaneous injections are contraindicated.