What Factors Affect Phenergan® Dosage?

Phenergan®, sometimes known by its generic name of promethazine, is a potent antihistamine. Antihistamines prevent a compound involved in the allergic response, known as histamine, from binding to cell receptors and having a negative effect on the body. For this reason, it is used for severe allergies. It is also sometimes used to treat nausea and insomnia, although the phenergan® dosage used for each purpose can vary. Age of the person taking this drug, as well as other factors, can sometimes influence the necessary dose for these various uses.

Typically, adults can take a phenergan® dosage of up to 25 milligrams (mg) at night in order to treat allergies. Due to the efficiency this drug has at absorbing into the body through different routes, 25 mg is used whether the drug is given as an oral tablet or syrup, or provided in a suppository. Alternately, smaller doses, ranging from 6.25 mg to 12.5 mg, may be taken at equal intervals during the day to control allergies with a minimal level of sedation.

Nausea with a known cause can be controlled with this drug. A phenergan® dosage of 25 mg can be given to adults for this purpose, and, as needed, a maintenance dose of 12.5 mg to 25 mg can be provided. Children generally take a reduced dose for this purpose, based on their body weight. The usual reduced dose is 0.5 mg per 1 kilogram (kg), or 2.2 pounds (lb) of body weight, for both initial and maintenance doses. Both children and adults may sometimes find it advantageous to take this drug in a suppository for this purpose, if tablets cannot successfully be held down.

Adults and children may sometimes find this compound useful for its sleep-inducing properties in the treatment of insomnia. Commonly, a phenergan® dosage of 25 mg to 50 mg, depending on the body weight, is used by adults for this function. Reduced dosages are often used when provided to children for assisting with sleep, with 12.5 mg to 25 mg being the most common amounts given.

Sedation before surgery can also be accomplished with promethazine. Similar dosages for insomnia are provided the night before surgery. Depending on the other sedatives that are provided, however, a lower phenergan® dosage may be desirable to avoid potentially harmful interactions. Classes of drugs like benzodiazepines and barbiturates, which are common sedatives, should also have their doses lowered when mixed with phenergan® for this purpose.