PHENERGAN VC
Clinical safety rating: caution
Comprehensive clinical and safety monograph for PHENERGAN VC (PHENERGAN VC).
Phenergan VC is a combination of promethazine (a phenothiazine derivative with antihistaminic, sedative, antiemetic, and anticholinergic effects) and phenylephrine (a sympathomimetic amine that acts as a decongestant via alpha-1 adrenergic receptor agonism). Promethazine antagonizes H1 receptors, thereby suppressing allergic reactions and motion sickness. Phenylephrine causes vasoconstriction in the nasal mucosa, reducing congestion.
| Metabolism | Promethazine undergoes hepatic metabolism primarily via CYP2D6 and to a lesser extent by other CYP enzymes. Phenylephrine is metabolized in the liver by monoamine oxidase (MAO) and sulfotransferase. |
| Excretion | Renal: 70-80% as metabolites; biliary/fecal: 20-30%. |
| Half-life | 9-16 hours; prolonged in hepatic impairment. |
| Protein binding | 76-90% bound to albumin. |
| Volume of Distribution | 13-18 L/kg; extensive tissue distribution. |
| Bioavailability | Oral: 25-70% due to first-pass effect; IM: 85-95%. |
| Onset of Action | Oral: 15-60 minutes; IM: 10-20 minutes. |
| Duration of Action | 6-12 hours; longer in elderly or hepatic impairment. |
| Molecular Weight | 340.9 |
10-20 mL orally every 4-6 hours as needed; each 5 mL contains 6.25 mg promethazine HCl and 5 mg phenylephrine HCl.
| Dosage form | SYRUP |
| Renal impairment | GFR 30-60 mL/min: administer with caution; GFR <30 mL/min: avoid use due to risk of accumulation of promethazine metabolites. |
| Liver impairment | Child-Pugh Class A: no adjustment needed; Child-Pugh Class B: reduce dose by 50%; Child-Pugh Class C: contraindicated. |
| Pediatric use | Children 2-5 years: 5-10 mL orally every 4-6 hours; 6-12 years: 10-15 mL orally every 4-6 hours; not recommended for children under 2 years due to risk of respiratory depression. |
| Geriatric use | Initiate at the lower end of the dosing range (e.g., 10 mL orally every 6 hours) due to increased sensitivity to anticholinergic effects and risk of sedation, confusion, and hypotension; avoid prolonged use. |
| 1st trimester | Phenergan VC contains promethazine, which has been associated with congenital malformations in some studies, though data are limited. Use only if clearly needed. |
| 2nd trimester | Limited data; potential for adverse effects on fetal development. Use only if benefit outweighs risk. |
| 3rd trimester | Avoid near term due to potential for respiratory depression in neonate and other adverse effects (e.g., extrapyramidal signs). |
Clinical note
Comprehensive clinical and safety monograph for PHENERGAN VC (PHENERGAN VC).
| Placental transfer | Promethazine crosses the placenta; documented in human studies. |
| Breastfeeding | Promethazine is excreted into breast milk in small amounts. May cause drowsiness or irritability in nursing infants. Use with caution, especially in preterm infants or those with respiratory instability. |
■ FDA Black Box Warning
WARNING: RESPIRATORY DEPRESSION IN CHILDREN. Promethazine is contraindicated in children younger than 2 years due to the risk of fatal respiratory depression. Use in children aged 2 years and older with caution and at lowest effective dose.
| Serious Effects |
Hypersensitivity to promethazine or phenothiazinesComatose statesConcurrent use of MAOIsSevere CNS depressionRespiratory symptoms in children under 2 yearsNewborn or premature infants
| Precautions | Respiratory depression: Avoid in children <2 years; use caution in patients with respiratory conditions like asthma or COPD., CNS depression: May cause drowsiness; avoid with alcohol or other CNS depressants., Anticholinergic effects: Use caution in patients with glaucoma, prostatic hypertrophy, or pyloroduodenal obstruction., Cardiovascular effects: Phenylephrine may cause hypertension, arrhythmias; use caution in heart disease, hyperthyroidism, diabetes., Extrapyramidal symptoms: Rare but possible with promethazine., Neuroleptic malignant syndrome: Discontinue if suspected., Drug interactions: MAO inhibitors, beta-blockers, other antihypertensives. |
| Food/Dietary |
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| Lactation Rating | L3 - Moderately Safe |
| Teratogenic Risk | First trimester: Limited human data; animal studies show no consistent malformations. Second/third trimester: Risk of neonatal respiratory depression, hypotonia, and withdrawal if used near term. Avoid in late pregnancy due to risk of Kernicterus in jaundiced neonates (sulfite component). |
| Fetal Monitoring | Monitor maternal blood pressure and heart rate due to phenylephrine (vasoconstrictor). Fetal heart rate monitoring if used during labor. Assess neonatal respiratory status and alertness if used near term. |
| Fertility Effects | No human data on fertility impairment. Animal studies show no significant reproductive toxicity. Phenylephrine may reduce uterine blood flow transiently but clinical relevance unknown. |
| Avoid alcohol and grapefruit juice. Alcohol increases CNS depression; grapefruit juice may enhance phenylephrine effects. No significant food restrictions otherwise. |
| Clinical Pearls | PHENERGAN VC combines promethazine (an antihistamine/antiemetic) and phenylephrine (a decongestant). Avoid use in children <2 years due to risk of fatal respiratory depression. Monitor for CNS depression, especially with concurrent CNS depressants. Contraindicated in patients with severe hypertension or coronary artery disease due to phenylephrine component. |
| Patient Advice | Do not use in children under 2 years old due to risk of serious breathing problems. · May cause drowsiness; avoid driving or operating heavy machinery until you know how this medication affects you. · Avoid alcohol and other sedatives while taking this medication. · Phenylephrine can raise blood pressure; monitor if you have high blood pressure or heart problems. · Take folic acid as directed to prevent neural tube defects. · Do not exceed recommended dose; consult your doctor if symptoms persist. |