Page 166 - 2026 SMOG

PROMETHAZINE (PHENERGAN)
Class/Mechanism of Action
• Phenothiazine derivative, Antiemetic, Histamine H Antagonist, Sedative
1
Blocks postsynaptic dopaminergic receptors in the brain; has a strong alpha-adrenergic blocking effect
and depresses the release of hypothalamic and hypophyseal hormones; reduces stimuli to the reticular
system.
˚ Onset of action—IV: 5min; Duration: 4–6hr
Indications
• Labeled Indications
Symptomatic treatment for allergic conditions; antiemetic; motion sickness; sedative; adjunct to
˚ postoperative analgesia and anesthesia
• Off-Label Indications
˚ Treatment of nausea and vomiting of pregnancy
Contraindications
• Hypersensitivity to promethazine, phenothiazine allergy, or any component of the formulation
• Coma
• Children <2 years old
• Intra-arterial and SubQ administration
• IV concentrations greater than 1mg/mL: greater risk for tissue necrosis
Adverse Reactions/Precautions
• May cause bradycardia, hyper/hypotension, nonspecific QT changes, orthostatic hypotension,
tachycardia. A life-threatening arrhythmia has occurred with a normal dosage.
• May cause extrapyramidal symptoms (pseudoparkinsonism, acute dystonic reactions, akathisia, etc.)
• Avoid use in severe respiratory disease (asthma, COPD), and in patients using other sedatives or
depressants: may lead to respiratory depression.
• Vesicant (causes blisters): can cause severe tissue injury regardless of the route of delivery
Deep IM injection or IV inline
˚ For IV, ensure proper needle/catheter venous placement; avoid extravasation. Slow IVP over 1min
• ˚ Pregnancy: Category C
• Lactation: Not recommended
Dose/Administration
PEDIATRIC
ADULT
(Always reference Broselow Tape)
Antiemetic Antiemetic
• IM/IV push over >1min • IM/IV
12.5mg not to exceed 25mg. May repeat Children ≥2 years: 0.25–0.5mg/kg 4–6 times a
˚ 12.5mg once after 10min if the first dose is ˚ day prn (max: 12.5mg/dose)
ineffective. Subsequent dose of 25mg may be Preoperative Analgesia/Hypnotic Adjunct
given q4–6hr • IM/IV
˚ Can dilute with 10–20mL of NS Children ≥2 years: 1.1mg/kg in combination
Sedation, Analgesia/Hypnotic Adjunct ˚ with an analgesic or hypnotic (at reduced
• IM/IV dosage) and with an atropine like agent (at
25–50mg in combination with analgesic or appropriate dosage)
˚ hypnotic (at reduced dosage)
Note: Promethazine dosage should not exceed half
Allergic Conditions (Including Allergic Reactions of the suggested adult dosage
to Blood or Plasma)
• IM/IV
˚ 25mg; may repeat in 2hr prn

158 • MEDICATIONS