Promethazine Dosage

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Usual Adult Dose for Anaphylaxis

Parenteral: 25 mg IV or IM once, followed by close observation for response. This dose may be repeated within 2 hours if needed. Oral therapy should be started as soon as feasible if continued medication is required.

Oral: 25 mg orally once. This dose may be repeated every 4 hours as needed.

Rectal: 25 mg administered rectally once. This dose may be repeated every 4 hours as needed.

Usual Adult Dose for Allergic Reaction

Oral or rectal: 12.5 mg before meals and 25 mg at bedtime, if necessary. Alternatively, a single 25 mg dose given at bedtime or 6.25 mg to 12.5 mg three times daily.
IM or IV: 25 mg, may repeat in 2 hours if necessary.

Usual Adult Dose for Allergic Rhinitis

Parenteral: 25 mg IV or IM, followed by close observation for response. This dose may be repeated within 2 hours if needed. Oral therapy should be started as soon as feasible if continued medication is required.

Oral: 25 mg at bedtime. Alternatively, 12.5 mg may be administered before the evening meal and again at bedtime for antihistamine effects.

Rectal: 25 mg at bedtime. Alternatively, 12.5 mg may be administered before the evening meal and again at bedtime for antihistamine effects.

The safety of promethazine for long-term treatment of allergic rhinitis has not been established.

Usual Adult Dose for Light Sedation

Parenteral: 25 mg IV or IM once, followed by close observation for response. An additional dose, up to 50 mg, may be administered to achieve the desired clinical effect.

Oral: 25 mg once. An additional dose, up to 50 mg, may be administered to achieve the desired clinical effect.

Rectal: 25 mg once. An additional dose, up to 50 mg, may be administered to achieve the desired clinical effect.

Usual Adult Dose for Motion Sickness

Oral or rectal: 25 mg 30 to 60 minutes before departure, then every 12 hours as needed.

Usual Adult Dose for Nausea/Vomiting

Oral, rectal, IM or IV: 12.5 to 25 mg every 4 to 6 hours as needed.

Usual Adult Dose for Opiate Adjunct

Oral, rectal, IM or IV: 25 to 50 mg every 4 hours as needed to augment the effects of concomitantly administered opioids.

Usual Adult Dose for Urticaria

Parenteral: 25 mg IV or IM, followed by close observation for response. This dose may be repeated within 2 hours if needed. Oral therapy should be started as soon as feasible if continued medication is required.

Oral: 25 mg at bedtime. Alternatively, 12.5 mg may be administered before the evening meal and again at bedtime for antihistamine effects.

Rectal: 25 mg at bedtime. Alternatively, 12.5 mg may be administered before the evening meal and again at bedtime for antihistamine effects.

Usual Adult Dose for Sedation

Oral, rectal, IM or IV: 25 to 50 mg/dose.

Usual Adult Dose for Vertigo

Acute Vertigo:
Initial: 25 mg IM, IV, orally, or by suppository.
Maintenance: 12.5 to 50 mg every 4 to 8 hours.

Maximum daily dose should not exceed 75 mg.

Usual Pediatric Dose for Allergic Reaction

Greater than or equal to 2 years: oral or rectal: 0.1 mg/kg/dose every 6 hours during the day and 0.5 mg/kg/dose at bedtime as needed.

Usual Pediatric Dose for Motion Sickness

Greater than or equal to 2 years: Oral or rectal: 0.5 mg/kg (not to exceed 25 mg) 30 minutes to 1 hour before departure, then every 12 hours as needed.

Usual Pediatric Dose for Nausea/Vomiting

Greater than or equal to 2 years: oral, rectal, IM or IV: 0.25 to 1 mg/kg/dose (not to exceed 25 mg) 4 to 6 times a day as needed.

Usual Pediatric Dose for Sedation

Greater than or equal to 2 years: Sedation: oral, IM, IV, or rectal: 0.5 to 1 mg/kg/dose (not to exceed 25 mg) every 6 hours as needed.

Greater than or equal to 2 years: Preoperative analgesia/hypnotic adjunct: IM, IV: 1.1 mg/kg once in combination with an analgesic or hypnotic (at reduced dosage) and with an atropine-like agent (at appropriate dosage). Note: Promethazine dosage should not exceed half of suggested adult dosage.

Renal Dose Adjustments

It is generally recommended that dosage selection for the elderly be started at the low end of the dosage range because of the greater frequency of decreased renal function reported in this population.

Liver Dose Adjustments

It is generally recommended that dosage selection for the elderly be started at the low end of the dosage range because of the greater frequency of decreased hepatic function reported in this population.

Dose Adjustments

65 years and older: In general, the therapeutic requirements for sedative drugs in this population tend to be lower. The manufacturer recommends a reduction in the dose of the tablets and the suppositories.

Precautions

Promethazine tablets and suppositories are contraindicated in pediatric patients less than 2 years of age because of the potential for fatal respiratory depression.

Caution should be exercised when administering promethazine tablets and suppositories to pediatric patients 2 years of age or older because of the potential for fatal respiratory depression. Respiratory depression and apnea, sometimes associated with death, are strongly associated with promethazine products and are not directly related to individualized weight-based dosing, which might otherwise permit safe administration. Concomitant administration of promethazine products with other respiratory depressants has an association with respiratory depression, and sometimes death, in pediatric patients.

Central and obstructive apneas have been observed in infants given promethazine. Promethazine has been implicated by some as a possible cause of the Sudden Infant Death Syndrome (SIDS).

Antiemetics are not recommended for treatment of uncomplicated vomiting in pediatric patients, and their use should be limited to prolonged vomiting of known etiology. The extrapyramidal symptoms which can occur secondary to promethazine tablets and suppositories administration may be confused with the CNS signs of undiagnosed primary disease, e.g., encephalopathy or Reye's syndrome. The use of promethazine should be avoided in pediatric patients whose signs and symptoms may suggest Reye's syndrome or other hepatic diseases.

Promethazine injectable formulation is indicated for deep IM injection or IV administration only. Extreme care should be taken to avoid intra-arterial injection during the use of parenteral promethazine. Inadvertent intra-arterial injection carries a high risk of distal necrosis and frequently requires amputation of the affected limb.

Promethazine may cause severe drowsiness and it can impair the mental and/or physical ability needed to drive a vehicle, ride a bicycle, and/or operate heavy machinery.

A potentially fatal syndrome complex also called Neuroleptic Malignant Syndrome (NMS) has occurred with promethazine alone or in combination with antipsychotic drugs. Symptom presentation include hyperpyrexia, muscle rigidity, altered mental status and evidence of autonomic instability (irregular pulse or blood pressure, tachycardia, diaphoresis and cardiac dysrhythmias).

Promethazine tablets and suppositories are contraindicated in comatose patients.

Respiratory depression, potentially fatal, may occur with the use of promethazine. Avoid the use of promethazine in patients with compromised respiratory function (e.g., COPD, sleep apnea). Antihistamines are contraindicated for use in the treatment of lower respiratory tract symptoms including asthma.

Promethazine should be used with caution in patients with seizure disorders because it may lower the seizure threshold. Similarly, if used with other medications that may affect seizure threshold such as narcotics or local anesthetics.

As with other anticholinergic drugs, caution is recommended when promethazine is used in patients with narrow-angle glaucoma, prostatic hypertrophy, stenosing peptic ulcer, pyloroduodenal obstruction, or bladder neck obstruction.

Cholestatic jaundice has been associated with the use of promethazine.

Dialysis

Promethazine is not dialyzable.

Other Comments

Promethazine may interfere with the following tests:
Pregnancy test - Diagnostic pregnancy tests based on immunologic reactions between HCG and anti-HCG, resulting in false-positive or false-negative interpretations.
Glucose tolerance test- Increase in glucose tolerance along with increase in blood glucose have been reported.

Avoid prolonged exposure to the sun.

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