promethazine hydrochloride

promethazine hydrochloride

(proe meth' a zeen)

Phenadoz, Phenergan

Pregnancy Category C

Drug classes

Phenothiazine

Dopaminergic blocking agent

Antihistamine

Antiemetic

Anti-motion sickness drug

Sedative or hypnotic

Therapeutic actions

Selectively blocks H₁ receptors, diminishing the effects of histamine on cells of the upper respiratory tract and eyes and decreasing the sneezing, mucus production, itching, and tearing that accompany allergic reactions in sensitized people exposed to antigens; blocks cholinergic receptors in the vomiting center that are believed to mediate the nausea and vomiting caused by gastric irritation, by input from the vestibular apparatus (motion sickness, nausea associated with vestibular neuritis), and by input from the chemoreceptor trigger zone (drug- and radiation-induced emesis); depresses the RAS, including the parts of the brain involved with wakefulness.

Indications

·        Symptomatic relief of perennial and seasonal allergic rhinitis, vasomotor rhinitis, allergic conjunctivitis; mild, uncomplicated urticaria and angioedema; amelioration of allergic reactions to blood or plasma; dermatographism, adjunctive therapy (with epinephrine and other measures) in anaphylactic reactions

·        Treatment and prevention of motion sickness; prevention and control of nausea and vomiting associated with anesthesia and surgery

·        Preoperative, postoperative, or obstetric sedation

·        Adjunct to analgesics to control postoperative pain

·        Adjunctive IV therapy with reduced amounts of meperidine or other opioid analgesics in special surgical situations, such as repeated bronchoscopy, ophthalmic surgery, or in poor-risk patients

Contraindications and cautions

·        Contraindicated with hypersensitivity to antihistamines or phenothiazines, coma or severe CNS depression, bone marrow depression, vomiting of unknown cause, concomitant therapy with MAOIs, lactation (lactation may be inhibited).

·        Use cautiously with lower respiratory tract disorders (may cause thickening of secretions and impair expectoration), glaucoma, prostatic hypertrophy, CV disease or hypertension, breast cancer, thyrotoxicosis, pregnancy (jaundice and extrapyramidal effects in infants; drug may inhibit platelet aggregation in neonate if taken by mother within 2 wk of delivery), children (antihistamine overdose may cause hallucinations, seizures, and death), a child with a history of sleep apnea, a family history of SIDS, or Reye's syndrome (may mask the symptoms of Reye's syndrome and contribute to its development), the elderly (more likely to cause dizziness, sedation, syncope, toxic confusional states, hypotension, and extrapyramidal effects).

Available forms

Tablets—12.5, 25, 50 mg; syrup—6.25, 25 mg/5 mL; suppositories—12.5, 25, 50 mg; injection—25, 50 mg/mL

Dosages

ADULTS

·        Allergy: Average dose is 25 mg PO or by rectal suppository, preferably hs. If necessary, 12.5 mg PO before meals and hs; 25 mg IM or IV for serious reactions. May repeat within 2 hr if necessary.

·        Motion sickness: 25 mg PO bid. Initial dose should be scheduled 30–60 min before travel; repeat in 8–12 hr if necessary. Thereafter, give 25 mg on arising and before evening meal.

·        Nausea and vomiting: 25 mg PO; repeat doses of 12.5–25 mg as needed, q 4–6 hr. Give rectally or parenterally if oral dosage is not tolerated. 12.5–25 mg IM or IV, not to be repeated more frequently than q 4–6 hr.

·        Sedation: 25–50 mg PO, IM, or IV.

·        Preoperative use: 50 mg PO the night before, or 50 mg with an equal dose of meperidine and the required amount of belladonna alkaloid.

·        Postoperative sedation and adjunctive use with analgesics: 25–50 mg PO, IM, or IV.

·        Labor: 50 mg IM or IV in early stages. When labor is established, 25–75 mg with a reduced dose of opioid. May repeat once or twice at 4-hr intervals. Maximum dose within 24 hr is 100 mg.

PEDIATRIC PATIENTS > 2 YR

·        Allergy: 25 mg PO hs or 6.25–12.5 mg tid.

·        Motion sickness: 12.5–25 mg PO or rectally bid.

·        Nausea and vomiting: 1 mg/kg IM q 4–6 hr as needed.

·        Sedation: 12.5–25 mg PO or 12.5–25 mg PO or rectally hs q 4–6 hr.

·        Preoperative use: 1 mg/kg PO in combination with an equal dose of meperidine and the required amount of an atropine-like drug.

·        Postoperative sedation and adjunctive use with analgesics: 1 mg/kg PO, IM, IV, or rectally.

Pharmacokinetics

Route	Onset	Duration
Oral	20 min	12 hr
IM	20 min	12 hr
IV	3–5 min	12 hr

Metabolism: Hepatic; T_1/2: Unknown

Distribution: Crosses placenta; enters breast milk

Excretion: Urine

IV facts

Preparation: Dilute to a concentration no greater than 25 mg/mL.

Infusion: Infuse no faster than 25 mg/min.

Incompatibilities: Do not combine with aminophylline, chloramphenicol, heparin, hydrocortisone, methicillin, pentobarbital, thiopental.

Y-site incompatibilities: Do not give with cefoperazone, foscarnet, heparin, hydrocortisone, potassium chloride.

Adverse effects

·        CNS: Dizziness, drowsiness, poor coordination, confusion, restlessness, excitation, seizures, tremors, headache, blurred vision, diplopia, vertigo, tinnitus

·        CV: Hypotension, palpitations, bradycardia, tachycardia, extrasystoles

·        Dermatologic: Urticaria, rash, photosensitivity, chills

·        GI: Epigastric distress, nausea, vomiting, diarrhea, constipation

·        GU: Urinary frequency, dysuria, urinary retention, decreased libido, impotence

·        Hematologic: Hemolytic anemia, hypoplastic anemia, thrombocytopenia, leukopenia, agranulocytosis, pancytopenia

·        Respiratory: Thickening of bronchial secretions; chest tightness; dry mouth, nose, and throat; respiratory depression; suppression of cough reflex, potential for aspiration

·        Other: Tingling, heaviness and wetness of the hands

Interactions

·        Additive anticholinergic effects with anticholinergic drugs

·        Increased frequency and severity of neuromuscular excitation and hypotension with methohexital, thiamylal, phenobarbital anesthetic, thiopental

·        Enhanced CNS depression with alcohol

Nursing considerations

Assessment

·        History: Hypersensitivity to antihistamines or phenothiazines, severe CNS depression, bone marrow depression, vomiting of unknown cause, concomitant therapy with MAOIs, lactation, lower respiratory tract disorders, glaucoma, prostatic hypertrophy, CV disease or hypertension, breast cancer,thyrotoxicosis, pregnancy, history of sleep apnea or a family history of SIDS, child with Reye's syndrome

·        Physical: Weight, T; reflexes, orientation, IOP; P, BP, orthostatic BP; R, adventitious sounds; bowel sounds and normal output, liver evaluation; urinary output, prostate size; CBC; urinalysis; LFTs, renal and thyroid function tests

Interventions

·        Do not give tablets, rectal suppositories to children < 2 yr.

·        Give IM injections deep into muscle.

·        Do not administer subcutaneously; tissue necrosis may occur.

·        WARNING: Do not administer intra-arterially; arteriospasm and gangrene of the limb may result.

·        Reduce dosage of barbiturates given concurrently with promethazine by at least half; arrange for dosage reduction of opioid analgesics given concomitantly by one-fourth to one-half.

Teaching points

·        Take drug exactly as prescribed.

·        Avoid using alcohol.

·        Avoid driving or engaging in other dangerous activities if dizziness, drowsiness, or vision changes occur.

·        Avoid prolonged exposure to sun, or use a sunscreen or covering garments.

·        Maintain fluid intake, and use precautions against heat stroke in hot weather.

·        Report sore throat, fever, unusual bleeding or bruising, rash, weakness, tremors, impaired vision, dark urine, pale stools, yellowing of the skin or eyes.

Adverse effects in Italic are most common; those in Bold are life-threatening.