Phenothiazine (FEE-noe-THYE-a-zeen)-derivative antihistamines are used to relieve or prevent the symptoms of hay fever and other types of allergy.
Promethazine is a phenothiazine in the same class of drugs as chlorpromazine (Thorazine) and trifluoperazine (Stelazine);

Antihistamines are used to relieve or prevent the symptoms of your medical problem. Take them only as directed . Do not take more of them and do not take them more often than recommended on the label, unless otherwise directed by your doctor. To do so may increase the chance of side effects

Sore throat and fever; unusual bleeding or bruising; unusual tiredness or weakness.

Promethazine should not be taken with any of the MAO (mono-amine oxidase) inhibitor-class of antidepressants, for example, isocarboxazid (Marplan), phenelzine (Nardil), tranylcypromine (Parnate), and procarbazine (Matulane), since the effects of both drugs add to each other and lead to complications

In case of overdose, call your local poison control center in the USA at 1-800-222-1222. If the victim has collapsed or is not breathing, call local emergency services at 911.

Excessive sedation may occur when promethazine is combined with other medications that depress the central nervous system (brain). Such drugs include ethanol, barbiturates, anti-anxiety medications, sedatives, other phenothiazines, and narcotic pain medications.

Take the missed dose as soon as you remember it. However, if it is almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one

They work by preventing the effects of a substance called histamine, which is produced by the body. Histamine can cause itching, sneezing, runny nose, and watery eyes. Also, in some persons histamine can close up the bronchial tubes (air passages of the lungs) and make breathing difficult.

Some of these antihistamines are also used to prevent motion sickness, nausea, vomiting, and dizziness. In addition, some of them may be used to help people go to sleep and control their anxiety before or after surgery. Phenothiazine-derivative antihistamines may also be used for other conditions as determined by your doctor

Keep this medication in the carton or container it came in, tightly closed, and out of reach of children. Store promethazine tablets and liquid at room temperature and away from excess heat and moisture (not in the bathroom). Store promethazine suppositories in the refrigerator. Protect the medication from light.

When taking phenothiazine-derivative antihistamines on a regular basis, make sure your doctor knows if you are taking large amounts of aspirin at the same time (as for arthritis or rheumatism). Effects of too much aspirin, such as ringing in the ears, may be covered up by the antihistamine.

Phenothiazine-derivative antihistamines will add to the effects of alcohol and other CNS depressants (medicines that slow down the nervous system, possibly causing drowsiness).