HYDROCODONE BITARTRATE AND HOMATROPINE METHYLBROMIDE
Clinical safety rating: avoid
CNS depressants including alcohol and benzodiazepines increase sedation risk Life-threatening respiratory depression may occur.
Hydrocodone is a semisynthetic opioid agonist that binds to mu-opioid receptors in the CNS, inhibiting ascending pain pathways and altering pain perception. Homatropine methylbromide is an anticholinergic agent that reduces gastrointestinal motility and secretions.
| Metabolism | Hydrocodone: primarily hepatic via CYP2D6 and CYP3A4 to hydromorphone, norhydrocodone, and other metabolites. Homatropine methylbromide: poorly absorbed; metabolized via ester hydrolysis and renal excretion. |
| Excretion | Hydrocodone and its metabolites are primarily excreted renally. Approximately 60% of a dose is eliminated in urine as unchanged drug and conjugates, with less than 5% excreted in feces. Homatropine methylbromide is a quaternary ammonium compound that is poorly absorbed and excreted mainly unchanged in feces via biliary elimination. |
| Half-life | The terminal elimination half-life of hydrocodone is approximately 3.8-4.5 hours in adults, though it may be prolonged in hepatic impairment or elderly patients. Homatropine methylbromide has a half-life of about 2-3 hours. |
| Protein binding | Hydrocodone is approximately 20-30% bound to plasma proteins, primarily albumin. Homatropine methylbromide has negligible protein binding (<5%). |
| Volume of Distribution | The volume of distribution for hydrocodone is approximately 3.3-4.7 L/kg, indicating extensive tissue distribution. For homatropine methylbromide, Vd is roughly 0.5-1 L/kg due to its quaternary structure limiting CNS penetration. |
| Bioavailability | Hydrocodone has an oral bioavailability of approximately 50-60% due to first-pass metabolism. Homatropine methylbromide is poorly absorbed orally, with bioavailability less than 10%. |
| Onset of Action | Oral administration: Onset of analgesic effect occurs within 20-30 minutes. Antitussive effect may begin within 15-30 minutes. |
| Duration of Action | Analgesic effect lasts approximately 4-6 hours. Antitussive effect persists for 4-6 hours. Duration may be shorter with immediate-release formulations. |
| Molecular Weight | Hydrocodone bitartrate: 494.5 g/mol; Homatropine methylbromide: 370.3 g/mol. Combined: average ~432.4 Da. |
Oral: 5 mg hydrocodone/1.5 mg homatropine every 4 to 6 hours as needed; maximum 30 mg hydrocodone per day.
| Dosage form | SYRUP |
| Renal impairment | GFR 30-89 mL/min: No adjustment. GFR 10-29 mL/min: Reduce dose by 25-50% or extend interval. GFR <10 mL/min: Reduce dose by 50% or extend interval to every 8-12 hours. |
| Liver impairment | Child-Pugh A: No adjustment. Child-Pugh B: Reduce dose by 50%. Child-Pugh C: Avoid use or use with extreme caution with 75% dose reduction. |
| Pediatric use | Children ≥6 years: 2.5 mg hydrocodone/0.75 mg homatropine orally every 4-6 hours as needed; maximum 15 mg hydrocodone per day. Children <6 years: Not recommended. |
| Geriatric use | Initiate at lowest effective dose (e.g., 2.5 mg hydrocodone/0.75 mg homatropine every 6 hours) with careful titration due to increased risk of falls, respiratory depression, and anticholinergic effects. |
| 1st trimester | Hydrocodone is pregnancy category C; associated with fetal opioid withdrawal and neural tube defects in animal studies. Use only if benefit outweighs risk. |
| 2nd trimester | Continued risk of fetal opioid dependence and preterm labor. Avoid prolonged use. |
| 3rd trimester | High risk of neonatal opioid withdrawal syndrome (NOWS) and respiratory depression. Avoid use, especially near term. |
Clinical note
CNS depressants including alcohol and benzodiazepines increase sedation risk Life-threatening respiratory depression may occur.
| FDA category | Positive |
| Placental transfer | Hydrocodone crosses the placenta readily; detectable in fetal plasma. Homatropine likely crosses but data limited. |
| Breastfeeding |
■ FDA Black Box Warning
Addiction, abuse, and misuse; life-threatening respiratory depression; accidental ingestion; neonatal opioid withdrawal syndrome; risks from concomitant use with benzodiazepines or other CNS depressants.
| Common Effects | Cough |
| Serious Effects |
Hypersensitivity to hydrocodone or homatropineSignificant respiratory depressionAcute or severe bronchial asthmaParalytic ileusConcurrent MAO inhibitor use or within 14 daysNarrow-angle glaucoma (homatropine component)
| Precautions | Respiratory depression, especially in elderly or debilitated; CNS depression; risk of opioid-induced hyperalgesia; increased intracranial pressure; severe hypotension; anticholinergic effects (constipation, urinary retention, blurred vision); tolerance and dependence; interactions with alcohol and other CNS depressants. |
| Food/Dietary |
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| Hydrocodone is excreted into breast milk in low concentrations (relative infant dose ~2-4%). However, CNS depression and withdrawal can occur in neonates. Homatropine may suppress lactation. Use lowest effective dose for shortest duration. |
| Lactation Rating | L3 (Moderately Safe) – cautious use; risk of infant sedation. |
| Teratogenic Risk | First trimester: Limited data; hydrocodone is not a major teratogen but opioid use may be associated with neural tube defects (RR 1.5-2.0) based on some studies. Homatropine methylbromide: No adequate studies; anticholinergics may be associated with minor malformations. Second trimester: No specific structural risks identified. Third trimester: Chronic use may cause neonatal opioid withdrawal syndrome (NOWS); anticholinergic effects may cause neonatal ileus or urinary retention. |
| Fetal Monitoring | Monitor maternal respiratory rate, sedation level, and bowel function. Assess fetal heart rate and uterine activity if used during labor (opioids may depress fetal heart rate variability). Neonatal monitoring for signs of opioid withdrawal (NOWS) for 48-72 hours after birth if used chronically. Consider urine drug screening if concern for misuse. |
| Fertility Effects | No specific studies on hydrocodone or homatropine methylbromide on human fertility. Chronic opioid use may cause hypothalamic-pituitary-gonadal axis suppression leading to hypogonadism, anovulation, and reduced sperm quality. Anticholinergics may cause vaginal dryness and potential impact on cervical mucus, but no direct fertility data. |
| Avoid grapefruit and grapefruit juice as they may increase hydrocodone levels. Avoid alcohol as it enhances CNS depression. No other significant food interactions. |
| Clinical Pearls | Hydrocodone bitartrate is an opioid agonist; homatropine methylbromide is an anticholinergic. The combination is used for cough suppression. Caution in patients with respiratory depression, COPD, or asthma. Monitor for CNS depression and constipation. The anticholinergic component may cause dry mouth, urinary retention, and blurred vision. Avoid use in patients with narrow-angle glaucoma or gastrointestinal obstruction. The recommended dose is one tablet every 4-6 hours; do not exceed 6 tablets per day. Use with caution in elderly or debilitated patients. Abrupt discontinuation may cause withdrawal symptoms. |
| Patient Advice | Take exactly as prescribed. Do not take more than recommended. · Avoid alcohol or other sedatives while taking this medication. · May cause drowsiness or dizziness. Do not drive or operate machinery until you know how it affects you. · Report difficulty breathing, severe constipation, or urinary retention. · May be habit forming. Do not share with others. · Store safely away from children and pets. · Do not stop abruptly without consulting your doctor. |