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. |
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 | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for PHENERGAN VC (PHENERGAN VC).
| Breastfeeding | Excreted in breast milk in low amounts (M/P ratio unknown for promethazine; phenylephrine M/P ratio ~0.3). Potential for infant sedation, irritability, and decreased milk supply (phenylephrine). Use only if benefit outweighs risk. |
| 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). |
■ 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 |
["Children younger than 2 years (black box warning)","Hypersensitivity to promethazine, phenylephrine, or any component","Asthma or other lower respiratory tract disease","Comatose states","Concurrent use of MAO inhibitors or within 14 days","Narrow-angle glaucoma","Symptomatic prostatic hypertrophy","Bladder neck obstruction","Hypertension or coronary artery disease (severe)"]
| 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."] |
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| 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. |