PHENAZINE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for PHENAZINE (PHENAZINE).
Phenazine is a phenothiazine neuroleptic that blocks postsynaptic D2 dopamine receptors in the mesolimbic and mesocortical pathways, thereby alleviating positive symptoms of schizophrenia. It also has anticholinergic (M1 receptor blockade), alpha1-adrenergic receptor antagonism, and H1-histamine receptor antagonism properties, contributing to its adverse effect profile.
| Metabolism | Extensively metabolized in the liver primarily via CYP2D6 and CYP3A4 isoenzymes; also undergoes glucuronidation and sulfation. |
| Excretion | Primarily renal (up to 80% as unchanged drug and metabolites), with approximately 15% biliary/fecal elimination. |
| Half-life | Terminal half-life approximately 6-10 hours; may be prolonged in hepatic or renal impairment, requiring dose adjustment. |
| Protein binding | Approximately 85-90%, primarily to albumin. |
| Volume of Distribution | Approximately 1.5 L/kg, indicating extensive tissue distribution. |
| Bioavailability | Oral: 50-60% due to first-pass metabolism; Intramuscular: 75-85%; Intravenous: 100%. |
| Onset of Action | Oral: 1-2 hours; Intramuscular: 20-40 minutes; Intravenous: immediate (within 5 minutes). |
| Duration of Action | Oral: 6-12 hours; Intramuscular: 8-12 hours; Intravenous: 4-6 hours; duration may be extended with higher doses or in slow metabolizers. |
| Action Class | H1 Antihistaminics (First Generation) |
| Brand Substitutes | Phenamin Syrup, Phenzee 5mg/5ml Syrup, Premagan Syrup, Prompt Syrup, Emispan Syrup |
Phenazine is not a standard pharmaceutical agent. The name is ambiguous and may refer to a chemical compound (phenazine) or a historical preparation. No established dosing exists.
| Dosage form | CAPSULE |
| Renal impairment | Not applicable; no established dosing for any phenazine-based drug product. |
| Liver impairment | Not applicable. |
| Pediatric use | No data available. |
| Geriatric use | No data available. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for PHENAZINE (PHENAZINE).
| Breastfeeding | Phenelzine is excreted into breast milk. The milk-to-plasma (M/P) ratio is not well established; limited data suggest small amounts. Breastfeeding is not recommended due to potential adverse effects in the infant (e.g., central nervous system stimulation, growth inhibition). Alternative therapies with better safety data should be considered. |
| Teratogenic Risk | Phenazine (phenelzine) is a monoamine oxidase inhibitor (MAOI). Teratogenic risk: First trimester: There are no adequate well-controlled studies in pregnant women; animal studies have shown adverse effects (e.g., decreased fetal weight, increased skeletal variations) at doses less than the maximum recommended human dose. Second and third trimesters: Potential risk of hypertensive crisis and serotonin syndrome in the neonate if used near term, as MAOIs may cross the placenta. Maternal use may be associated with neonatal withdrawal symptoms, including irritability and hypertonia. |
■ FDA Black Box Warning
Increased mortality in elderly patients with dementia-related psychosis. Phenazine is not approved for the treatment of dementia-related psychosis.
| Serious Effects |
Comatose states, CNS depression, known hypersensitivity to phenothiazines, bone marrow suppression, narrow-angle glaucoma, concurrent use of large amounts of ethanol or other CNS depressants, and severe hepatic impairment.
| Precautions | May cause tardive dyskinesia, neuroleptic malignant syndrome (NMS), QT prolongation (risk of torsades de pointes), hypotension, seizures, leukopenia/neutropenia/agranulocytosis, anticholinergic effects (e.g., constipation, urinary retention), weight gain, and hyperprolactinemia. |
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| Fetal Monitoring | Monitor maternal blood pressure and heart rate regularly due to risk of hypertensive crisis. Fetal monitoring: assess fetal growth via ultrasound and monitor for signs of adverse effects (e.g., tachycardia, irritability). Neonatal monitoring: observe for symptoms of withdrawal (e.g., hypertonia, jitteriness) and hypertensive crisis in the neonate after delivery. |
| Fertility Effects | Phenelzine may impair fertility in males by causing erectile dysfunction and ejaculatory disorders. In females, it may lead to menstrual irregularities or ovulatory dysfunction due to its effects on prolactin and neurotransmitter balance. Data on human fertility are limited, but potential for reversible reduction in fertility exists. |