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Promethazine is an antihistamine used to relieve allergic rhinitis (seasonal allergy) symptoms including sneezing, runny nose, itching, and watery eyes and itching and swelling associated with uncomplicated allergic skin reactions. It is also used as a sleep aid for surgical procedures and to prevent/treat motion sickness, nausea, and vomiting. Promethazine is available as a nonprescription product alone and in a combination product to treat symptoms of allergy, colds, and upper respiratory infections. It is also available in prescription products with codeine, to treat coughs associated with colds and upper respiratory infections.

Summary of Interactions with Vitamins, Herbs, & Foods

dnicon_Beneficial May Be Beneficial: Depletion or interference—This medication may deplete these substances from the body or interfere with how they work; extra intake may help replenish them.


dnicon_Beneficial May Be Beneficial: Side effect reduction and/or prevention—These substances may help reduce the likelihood and/or severity of a potential side effect caused by the medication.


dnicon_Beneficial May Be Beneficial: Supportive interaction—These substances may help this medication work better.


dnicon_Avoid Avoid: Reduces drug effectiveness—When taking this medication, avoid these substances as they may decrease the medication's absorption and/or activity in the body.


dnicon_Avoid Avoid: Adverse interaction—When taking this medication, avoid these substances, as the combination may cause undesirable or dangerous interactions.


dnicon_Check Check: Explanation needed—When taking this medication, read the article details and discuss them with your doctor or pharmacist before taking these substances.


An asterisk (*) next to an item in the summary indicates that the interaction is supported only by weak, fragmentary, and/or contradictory scientific evidence.

Interactions Details

Interactions with Herbs

Henbane (Hyoscyamus niger)

Antihistamines, including promethazine, can cause “anticholinergic” side effects such as dryness of mouth and heart palpitations. Henbane also has anticholinergic activity and side effects. Therefore, use with promethazine could increase the risk of anticholinergic side effects,1 though apparently no interactions have yet been reported with promethazine and henbane. Henbane should not be taken except by prescription from a physician trained in its use, as it is extremely toxic.

Interactions with Foods & Other Compounds


Promethazine causes drowsiness.2 Alcohol may intensify this effect and increase the risk of accidental injury.3 To prevent problems, people taking promethazine or promethazine-containing products should avoid alcohol.


Common brand names:

Phenadoz, Phenergan, Promethegan


1. Blumenthal M, ed. The Complete German Commission E Monographs. Austin, TX: American Botanical Council, 1998, 146.

2. Threlkeld DS, ed. Respiratory Drugs, Antihistamines. In Facts and Comparisons Drug Information. St. Louis, MO: Facts and Comparisons, May 1998, 192b–2c.

3. Threlkeld DS, ed. Respiratory Drugs, Antihistamines. In Facts and Comparisons Drug Information. St. Louis, MO: Facts and Comparisons, May 1998, 192b–2c.

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