ANTIHISTAMINES,PHENOTHIAZINE-DERIVATIVE (Systemic)

Some commonly used brand names are:

In the U.S.?

• Anergan 25 ²
• Anergan 50 ²
• Antinaus 50 ²
• Pentazine ²
• Phenazine 25 ²
• Phenazine 50 ²
• Phencen-50 ²
• Phenergan ²
• Phenergan Fortis ²
• Phenergan Plain ²
• Phenerzine ²
• Phenoject-50 ²
• Pro-50 ²
• Promacot ²
• Pro-Med 50 ²
• Promet ²
• Prorex-25 ²
• Prorex-50 ²
• Prothazine ²
• Prothazine Plain ²
• Shogan ²
• Tacaryl ¹
• V-Gan-25 ²
• V-Gan-50 ²

In Canada?

• Histantil ²
• Panectyl ³
• Phenergan ²

Another commonly used name for trimeprazine is alimemazine.

Category

• Antiemetic?Promethazine
• Antihistaminic, H ₁-receptor?Methdilazine; Promethazine; Trimeprazine
• Antivertigo agent?Promethazine
• Sedative-hypnotic?Promethazine; Trimeprazine

Description

Phenothiazine (FEE-noe-THYE-a-zeen)-derivativeantihistamines are used to relieve or prevent the symptoms of hay fever andother types of allergy. They work by preventing the effects of a substancecalled histamine, which is produced by the body. Histamine can cause itching,sneezing, runny nose, and watery eyes. Also, in some persons histamine canclose up the bronchial tubes (air passages of the lungs) and make breathingdifficult.

Some of these antihistamines are also used to prevent motion sickness,nausea, vomiting, and dizziness. In addition, some of them may be used tohelp people go to sleep and control their anxiety before or after surgery.

Phenothiazine-derivative antihistamines may also be used for other conditionsas determined by your doctor.

In the U.S. these antihistamines are available only with your doctor'sprescription. In Canada some are available without a prescription. However,your doctor may have special instructions on the proper dose of the medicinefor your medical condition.

These medicines are available in the following dosage forms:

Oral
• Methdilazine
  • Syrup (U.S.)
  • Tablets (U.S.)
  • Chewable tablets (U.S.)
• Promethazine
  • Syrup (U.S. and Canada)
  • Tablets (U.S. and Canada)
• Trimeprazine
  • Extended-release capsules
  • Syrup (Canada)
  • Tablets (Canada)

Parenteral
• Promethazine
  • Injection (U.S. and Canada)

Rectal
• Promethazine
  • Suppositories (U.S.)

Before Using This Medicine

In deciding to use a medicine,the risks of taking the medicine must be weighed against the good it willdo. This is a decision you and your doctor will make. For phenothiazine-derivativeantihistamines, the following should be considered:

Allergies?Tell your doctor if you have ever had any unusual orallergic reaction to these medicines or to phenothiazines. Also tell yourhealth care professional if you are allergic to any other substances, suchas foods, preservatives, or dyes.

Pregnancy?Methdilazine, promethazine, and trimeprazine havenot been studied in pregnant women. In animal studies, promethazine has notbeen shown to cause birth defects. However, other phenothiazine medicinescaused jaundice and muscle tremors in a few newborn babies whose mothers receivedthese medicines during pregnancy. Also, the newborn baby may have blood clottingproblems if promethazine is taken by the mother within 2 weeks before delivery.Before taking this medicine, make sure your doctor knows if you are pregnantor if you may become pregnant.

Breast-feeding?Small amounts of antihistamines pass into the breastmilk. Use by nursing mothers is not recommended since babies are more sensitiveto the side effects of antihistamines, such as unusual excitement or irritability.Also, with the use of phenothiazine-derivative antihistamines there is thechance that the nursing baby may be more at risk of having difficulty in breathingwhile sleeping or of the sudden infant death syndrome (SIDS). However, morestudies are needed to confirm this.

In addition, since these medicines tend to decrease the secretions of thebody, it is possible that the flow of breast milk may be reduced in some patients.

Children?Serious side effects, such as convulsions (seizures),are more likely to occur in younger patients and would be of greater riskto infants than to older children or adults. In general, children are moresensitive to the effects of antihistamines. Also, nightmares or unusual excitement,nervousness, restlessness, or irritability may be more likely to occur inchildren. The use of phenothiazine-derivative antihistaminesis not recommended in children who have a history of difficulty in breathingwhile sleeping, or a family history of sudden infant death syndrome (SIDS).

Children younger than 2 years of age should nottake promethazine because it may cause severe and sometimes fatal breathingand lung problems. Check with your doctor or pharmacistright away if you are unsure about whether or not your child or infant shouldbe taking promethazine.

Children who show signs of Reye's syndrome should not be given phenothiazine-derivativeantihistamines, especially by injection. Uncontrolled movements that may occurwith phenothiazine-derivative antihistamines may be mistakenly confused withsymptoms of Reye's syndrome.

Adolescents?Adolescents who show signs of Reye's syndrome shouldnot be given phenothiazine-derivative antihistamines, especially by injection.Uncontrolled movements that may occur with phenothiazine-derivative antihistaminesmay be mistakenly confused with symptoms of Reye's syndrome.

Older adults?Elderly patients are especially sensitive to theeffects of antihistamines. Confusion; difficult or painful urination; dizziness;drowsiness; feeling faint; or dryness of the mouth, nose, or throat may bemore likely to occur in elderly patients. Also, nightmares or unusual excitement,nervousness, restlessness, or irritability may be more likely to occur inelderly patients. In addition, uncontrolled movements may be more likely tooccur in elderly patients taking phenothiazine-derivative antihistamines.

Other medicines?Although certain medicines should not be usedtogether at all, in other cases two different medicines may be used togethereven if an interaction might occur. In these cases, your doctor may want tochange the dose, or other precautions may be necessary. When taking phenothiazine-derivativeantihistamines, it is especially important that your health care professionalknow if you are taking/receiving any of the following:

• Amoxapine (e.g., Asendin) or
• Antipsychotics (medicine for mental illness) or
• Methyldopa (e.g., Aldomet) or
• Metoclopramide (e.g., Reglan) or
• Metyrosine (e.g., Demser) or
• Pemoline (e.g., Cylert) or
• Pimozide (e.g., Orap) or
• Rauwolfia alkaloids (alseroxylon [e.g., Rauwiloid], deserpidine [e.g.,Harmonyl], rauwolfia serpentina [e.g., Raudixin], reserpine [e.g., Serpasil])?Sideeffects of these medicines, such as uncontrolled body movements, may becomemore severe and frequent if they are used together with phenothiazine-derivativeantihistamines

• Anticholinergics (medicine for abdominal or stomach spasms or cramps)?Sideeffects of phenothiazine-derivative antihistamines or anticholinergics, suchas dryness of mouth, may be more likely to occur

• Central nervous system (CNS) depressants (medicines that cause drowsiness)or
• Maprotiline or
• Tricyclic antidepressants (medicine for depression)?Effectsof CNS depressants or antihistamines, such as drowsiness, may become moresevere; also, taking maprotiline or tricyclic antidepressants may cause someside effects of antihistamines, such as dryness of mouth, to become more severe;taking promethazine with these medicines may make very serious lung problemsworse

• Contrast agent, injected into spinal canal?If you are havingan x-ray test of the head, spinal canal, or nervous system for which you aregoing to receive an injection into the spinal canal, phenothiazine-derivativeantihistamines may increase the chance of seizures; stop taking any phenothiazine-derivativeantihistamine 48 hours before the test and do not start taking it until 24hours after the test

• Levodopa?When used together with phenothiazine-derivative antihistamines,the levodopa may not work as it should

• Monoamine oxidase (MAO) inhibitor activity (isocarboxazid [e.g.,Marplan], isocarboxazid [e.g., Marplan], phenelzine [e.g., Nardil], procarbazine[e.g., Matulane], selegiline [e.g., Eldepryl], tranylcypromine [e.g., Parnate])?Ifyou are now taking or have taken within the past 2 weeks any of the MAO inhibitors,the side effects of the phenothiazine-derivative antihistamines may becomemore severe; these medicines should not be used together

Other medical problems?The presence of other medicalproblems may affect the use of antihistamines. Make sure you tell your doctorif you have any other medical problems, especially:

• Blood disease or
• Heart or blood vessel disease?These medicines may cause moreserious conditions to develop

• Airway blockage or
• Breathing/lung problems or
• Sleep apnea (stop breathing while asleep)?Promethazine shouldnot be used; may make condition much worse

• Comatose state (unconscious)?These medicines should not begiven to patients who are in a coma.

• Encephalopathy (brain disease) or
• Reye's syndrome?Phenothiazine-derivative antihistamines, especiallypromethazine, may increase the chance of uncontrolled movements. Promethazineuse should be avoided in children with these conditions.

• Enlarged prostate or
• Urinary tract blockage or difficult urination?Phenothiazine-derivativeantihistamines may cause urinary problems to become worse

• Epilepsy or
• Seizure disorders?Phenothiazine-derivative antihistamines,especially promethazine, may increase the chance of seizures

• Glaucoma?These medicines may cause a slight increase in innereye pressure that may worsen the condition

• Intestinal tract obstruction or
• Stomach ulcer?Phenothiazine-derivative antihistamines shouldbe used with caution. They may make the condition worse.

• Jaundice?Phenothiazine-derivative antihistamines may make thecondition worse

• Liver disease?Phenothiazine-derivative antihistamines may buildup in the body, which may increase the chance of side effects such as musclespasms

Proper Use of This Medicine

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

For patients taking this medicine by mouth:

• Antihistamines can be taken with food or a glass of water or milkto lessen stomach irritation if necessary.
• If you are taking the extended-release capsule form of this medicine, swallow it whole. Do not break, crush, or chewbefore swallowing.

For patients taking promethazine for motion sickness:

• Take this medicine 30 minutes to 1 hour before you begin to travel.

For patients using the suppository form of this medicine:

• To insert suppository: First remove the foil wrapper and moistenthe suppository with cold water. Lie down on your side and use your fingerto push the suppository well up into the rectum. If the suppository is toosoft to insert, chill the suppository in the refrigerator for 30 minutes orrun cold water over it before removing the foil wrapper.

For patients using the injection form of this medicine:

• If you will be giving yourself the injections, make sure you understandexactly how to give them. If you have any questions about this, check withyour health care professional.

Dosing?The dose of an antihistamine will be differentfor different patients. Follow your doctor's orders orthe directions on the label. The following information includes onlythe average doses of antihistamines. If your dose isdifferent, do not change it unless your doctor tells you to do so.

The number of capsules or tablets or teaspoonfuls of liquid that you takedepends on the strength of the medicine. Also, the numberof doses you take each day and the time between doses depends on whether youare taking a short-acting or long-acting form of antihistamine.

For methdilazine
• For regular (short-acting) oral dosageforms (tablets or liquid):
  • For allergy symptoms:
    • Adults and teenagers?8 milligrams (mg) every six to twelvehours as needed.
    • Children younger than 3 years of age?Use and dose must be determinedby your doctor.
    • Children 3 to 12 years of age?4 mg every six to twelve hoursas needed.

For promethazine
• For regular (short-acting) oral dosageforms (tablets or liquid):
  • For allergy symptoms:
    • Adults and teenagers?10 to 12.5 mg four times a day beforemeals and at bedtime; or 25 mg at bedtime as needed.
    • Children younger than 2 years of age?Should not be used
    • Children 2 years of age and older?Your doctor will determinedose based on the weight and/or size of the child. Children usually are given5 to 12.5 mg three times a day or 25 mg at bedtime as needed.
  • For nausea and vomiting:
    • Adults and teenagers?25 mg for the first dose, then 10 to 25mg every four to six hours if needed.
    • Children younger than 2 years of age?Should not be used
    • Children 2 years of age and older?Your doctor will determinedose based on the weight and/or size of the child. Children usually are given10 to 25 mg every four to six hours as needed.
  • For prevention of motion sickness:
    • Adults and teenagers?25 mg taken one-half to one hour beforetraveling. The dose may be repeated eight to twelve hours later if needed.
    • Children younger than 2 years of age?Should not be used
    • Children 2 years of age and older?Your doctor will determinedose based on the weight and/or size of the child. Children usually are given10 to 25 mg one-half to one hour before traveling. The dose may be repeatedeight to twelve hours later if needed.
  • For vertigo (dizziness):
    • Adults and teenagers?25 mg two times a day as needed.
    • Children younger than 2 years of age?Should not be used
    • Children 2 years of age and older?Your doctor will determinedose based on the weight and/or size of the child. Children usually are given10 to 25 mg two times a day as needed.
  • For use as a sedative:
    • Adults and teenagers?25 to 50 mg.
    • Children younger than 2 years of age?Should not be used
    • Children 2 years of age and older?Your doctor will determinedose based on the weight and/or size of the child. Children usually are given10 to 25 mg.
• For injection dosage form:
  • For allergy symptoms:
    • Adults and teenagers?25 mg injected into a muscle or into avein.
    • Children younger than 2 years of age?Use and dose must be determinedby your doctor.
    • Children 2 years of age and older?Your doctor will determinedose based on the weight and/or size of the child. Children usually are given6.25 to 12.5 mg injected into a muscle three times a day or 25 mg at bedtimeas needed.
  • For nausea and vomiting:
    • Adults and teenagers?12.5 to 25 mg injected into a muscle orinto a vein every four hours as needed.
    • Children younger than 2 years of age?Use and dose must be determinedby your doctor.
    • Children 2 years of age and older?Your doctor will determinedose based on the weight and/or size of the child. Children usually are given12.5 to 25 mg injected into a muscle every four to six hours as needed.
  • For use as a sedative:
    • Adults and teenagers?25 to 50 mg injected into a muscle orinto a vein.
    • Children younger than 2 years of age?Use and dose must be determinedby your doctor.
    • Children 2 years of age and older?Your doctor will determinedose based on the weight and/or size of the child. Children usually are given12.5 to 25 mg injected into a muscle.
• For suppository dosage form:
  • For allergy symptoms:
    • Adults and teenagers?25 mg inserted in rectum. Another 25-mgsuppository may be inserted two hours later if needed.
    • Children younger than 2 years of age?Should not be used
    • Children 2 years of age and older?Your doctor will determinedose based on the weight and/or size of the child. Children usually are given6.25 to 12.5 mg inserted into the rectum three times a day or 25 mg at bedtimeas needed.
  • For nausea and vomiting:
    • Adults and teenagers?25 mg inserted into the rectum for thefirst dose, then 12.5 to 25 mg every four to six hours if needed.
    • Children younger than 2 years of age?Should not be used
    • Children 2 years of age and older?Your doctor will determinedose based on the weight and/or size of the child. Children usually are given12.5 to 25 mg inserted into the rectum every four to six hours as needed.
  • For vertigo (dizziness):
    • Adults and teenagers?25 mg inserted into the rectum, two timesa day as needed.
    • Children younger than 2 years of age?Should not be used
    • Children 2 years of age and older?Your doctor will determinedose based on the weight and/or size of the child. Children usually are given12.5 to 25 mg inserted into the rectum two times a day as needed.
  • For use as a sedative:
    • Adults and teenagers?25 to 50 mg inserted into the rectum.
    • Children younger than 2 years of age?Should not be used
    • Children 2 years of age and older?Your doctor will determinedose based on the weight and/or size of the child. Children usually are given12.5 to 25 mg inserted into the rectum.

For trimeprazine
• For regular (short-acting) oral dosageforms (tablets or liquid):
  • For allergy symptoms:
    • Adults and teenagers?2.5 mg four times a day as needed.
    • Children younger than 2 years of age?Use and dose must be determinedby your doctor.
    • Children 2 to 3 years of age?1.25 mg at bedtime or three timesa day as needed.
    • Children 3 to 12 years of age?2.5 mg at bedtime or three timesa day as needed.
• For long-acting oral dosage forms (extended-releasecapsules):
  • For allergy symptoms:
    • Adults and teenagers?5 mg every twelve hours as needed.
    • Children younger than 6 years of age?Use and dose must be determinedby your doctor.
    • Children 6 to 12 years of age?5 mg once a day as needed.

Missed dose?If you are taking this medicine regularly and youmiss a dose, take it as soon as possible. However, if it is almost time foryour next dose, skip the missed dose and go back to your regular dosing schedule.Do not double doses.

Storage?To store this medicine:

• Keep out of the reach of children, since overdose may be very dangerousin children.
• Store away from heat and direct light.
• Do not store the capsule or tablet form of this medicine in the bathroommedicine cabinet, near the kitchen sink, or in other damp places. Heat ormoisture may cause the medicine to break down.
• Keep the liquid form of this medicine from freezing.
• Do not keep outdated medicine or medicine no longer needed. Be surethat any discarded medicine is out of the reach of children.

Precautions While Using This Medicine

Tellthe doctor in charge that you are taking this medicine before you have anyskin tests for allergies. The results of the tests may be affected by thismedicine.

When taking phenothiazine-derivative antihistamines on a regular basis,make sure your doctor knows if you are taking large amounts of aspirin atthe 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 alcoholand other CNS depressants (medicines that slow down the nervous system, possiblycausing drowsiness). Some examples of CNS depressants are sedatives, tranquilizers,or sleeping medicine; prescription pain medicine or narcotics; barbiturates;medicine for seizures; muscle relaxants; or anesthetics, including some dentalanesthetics. Check with your doctor before taking anyof the above while you are using this medicine.

Check with your doctor right away if you have symptoms of pale or bluelips, fingernails, or skin, difficult or troubled breathing, irregular, fast,slow or shallow breathing or shortness of breath. These could be signs ofa condition called respiratory depression.

Check with your doctor right away and stop taking your medicine (if directedby your doctor) if you have muscle rigidity, fever, difficult or fast breathing,seizures, fast heartbeat, increased sweating, loss of bladder control, unusuallypale skin, or tiredness or weakness. These may be symptoms of a serious conditioncalled neuroleptic malignant syndrome.

This medicine may cause some people to become drowsy or less alert thanthey are normally. Even if taken at bedtime, it may cause some people to feeldrowsy or less alert on arising. Make sure you know howyou react to the phenothiazine-derivative antihistamine you are taking beforeyou drive, use machines, or do anything else that could be dangerous if youare not alert.

Phenothiazine-derivative antihistamines may cause dryness of the mouth,nose, and throat. For temporary relief of mouth dryness, use sugarless candyor gum, melt bits of ice in your mouth, or use a saliva substitute. However,if your mouth continues to feel dry for more than 2 weeks, check with yourmedical doctor or dentist. Continuing dryness of the mouth may increase thechance of dental disease, including tooth decay, gum disease, and fungus infections.

This medicine controls nausea and vomiting. For this reason, it may coverup some of the signs of overdose caused by other medicines or the symptomsof appendicitis. This will make it difficult for your doctor to diagnose theseconditions. Make sure your doctor knows that you are taking this medicineif you have other symptoms of appendicitis such as stomach or lower abdominalpain, cramping, or soreness. Also, if you think you may have taken an overdoseof any medicine, tell your doctor that you are taking this medicine.

Side Effects of This Medicine

Along with its needed effects, a medicine may cause some unwanted effects.Although not all of these side effects may occur, if they do occur they mayneed medical attention.

Check with your doctor as soon as possible if any of the following sideeffects occur:

Less common or rare

Sore throat and fever; unusual bleedingor bruising; unusual tiredness or weakness

Incidence not known

Abdominal or stomach pain; area rash; black, tarry stools; bleeding gums; blood in urine or stools; bloody nose; bluish skin or lips; chest pain or discomfort; chills; clay-colored stools; confusion aboutidentity, place, and time; continuing ringing orbuzzing or other unexplained noise in ears; convulsions; cough or hoarseness; dark urine; decreased awareness or responsiveness; difficult or troubled breathing; difficulty in speaking; drooling; fainting; fever with or without chills; fixed position of eye; general feelingof tiredness or weakness; headache; hearing loss; heavier menstrual periods; high fever; high or lowblood pressure; hives or welts; hysteria; irregular, fast, slow, or shallow breathing; itching; large, hive-likeswelling on face, eyelids, lips, tongue, throat, hands, legs, feet, sex organs; lightheadedness; lossof balance control; loss of bladder control; loss of strength or energy; lower backor side pain; menstrual periods; mimicry of speech or movements; muscle pain or weakness; muscle spasm or jerking of all extremities; muscle trembling, jerking or stiffness; mutism; nausea; negativism; not breathing; painfulor difficult urination; pale or blue lips, fingernails,or skin; peculiar postures or movements, mannerisms,or grimacing; pinpoint red spots on skin; redness of skin; restlessness; seeing, hearing, or feeling things that are not there; severe muscle stiffness; severe musclestiffness; severe sleepiness; shortness of breath; shuffling walk; slow or irregular heartbeat; sore throat; sores, ulcers, or white spots on lips or in mouth; sticking out of tongue; stiffness of limbs; sudden loss of consciousness; swollen glands; tiredness; trouble thinking, speaking, or walking; twisting movements of body; uncontrolledmovements, especially of face, neck, and back; uncontrolledtwisting movements of neck; unpleasant breath odor; unusual bleeding or bruising; unusual tiredness or weakness; unusual weak feeling; unusually pale skin; vomiting of blood; weakness, numbness or tinglingin arms or legs; yellow eyes or skin

Symptoms of overdose

Clumsiness or unsteadiness; convulsions(seizures); drowsiness (severe); dryness of mouth, nose, or throat (severe); feelingfaint; flushing or redness of face; hallucinations (seeing, hearing, or feeling things that are notthere); muscle spasms (especially of neck and back); restlessness; shortnessof breath or troubled breathing; shuffling walk; tic-like (jerky) movements of head and face; trembling and shaking of hands; trouble in sleeping

Other side effects may occur that usually do not need medical attention.These side effects may go away during treatment as your body adjusts to themedicine. However, check with your health care professional if any of thefollowing side effects continue or are bothersome:

More common

Drowsiness (less common with methdilazine); thickening of mucus

Less common or rare

Blurred vision or any change in vision; burning or stinging of rectum (with rectal suppository); confusion; difficult or painful urination; dizziness; dryness of mouth, nose, orthroat; fast heartbeat; feeling faint; increased sensitivity of skin to sun; increased sweating; lossof appetite; nightmares; ringing or buzzing in ears; skin rash; unusual excitement, nervousness, restlessness, or irritability

Incidence not known

blistering, crusting, irritation, itching, or reddening of skin; cracked, dry, scaly skin; double vision; false or unusual sense of well being; lack of coordination; nasal stuffiness; nervousness; noisy breathing; relaxed and calm; seeing double; sleepiness or unusual drowsiness; sleeplessness; swelling; tightness in chest; trouble sleeping; unable to sleep; vomiting; wheezing

Other side effects not listed above may also occur in some patients. Ifyou notice any other effects, check with your health care professional.