ORAMORPH SR
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ORAMORPH SR (ORAMORPH SR).
Morphine is a full opioid agonist with relative selectivity for the mu-opioid receptor, although it can interact with other opioid receptors at higher doses. Binding to mu-opioid receptors in the central nervous system (CNS) and peripheral tissues results in analgesia, euphoria, sedation, respiratory depression, and physical dependence. Morphine also activates descending inhibitory pathways and inhibits ascending nociceptive transmission.
| Metabolism | Primarily metabolized via glucuronidation in the liver to morphine-3-glucuronide (M3G, major inactive metabolite) and morphine-6-glucuronide (M6G, active metabolite with analgesic and respiratory depressant effects). Minor metabolism via sulfation. Involved enzymes: UGT2B7 (primary), UGT1A1, UGT1A3, UGT1A8. CYP450 enzymes play a minimal role. |
| Excretion | Renal (approximately 90% as morphine-3-glucuronide and morphine-6-glucuronide, minor amounts of unchanged morphine, and other conjugates); biliary/fecal (approximately 10%). |
| Half-life | 2–4 hours in adults; in controlled-release formulation, effective half-life is prolonged due to sustained absorption. Clinically, steady-state is achieved in 1–2 days. |
| Protein binding | 30–35% bound, primarily to albumin. |
| Volume of Distribution | 3–5 L/kg (large Vd indicates extensive tissue distribution, including sequestration in skeletal muscle and fat). |
| Bioavailability | Oral (immediate-release): 20–40% (first-pass metabolism); Oral (controlled-release): approximately 15–30% (slightly lower due to slow release formulation). |
| Onset of Action | Oral (immediate-release): 30–60 minutes; Oral (controlled-release, ORAMORPH SR): 1–2 hours |
| Duration of Action | Oral (controlled-release, ORAMORPH SR): 8–12 hours; clinical note: analgesic effect may last up to 12 hours with steady-state dosing. |
| Molecular Weight | 285.34 |
10-30 mg orally every 8-12 hours, sustained-release; titrate as needed for pain.
| Dosage form | TABLET, EXTENDED RELEASE |
| Renal impairment | GFR 10-50 mL/min: administer 75% of usual dose every 12 hours; GFR <10 mL/min: administer 50% of usual dose every 12 hours. |
| Liver impairment | Child-Pugh Class A: no adjustment; Class B: reduce dose by 50% and monitor; Class C: reduce dose by 75% or consider alternative. |
| Pediatric use | 0.2-0.4 mg/kg/dose orally every 12 hours as sustained-release; maximum 1 mg/kg/dose; not recommended for children <6 months. |
| Geriatric use | Start at the low end of dosing range (e.g., 10 mg every 12 hours) and titrate cautiously due to increased sensitivity and risk of respiratory depression; consider renal function. |
| 1st trimester | Limited human data; animal studies show no evidence of teratogenicity at therapeutic doses. Risk of neural tube defects with high doses. Use only if clearly needed. |
| 2nd trimester | No malformation risk; may cause fetal dependence and withdrawal. Use with caution. |
| 3rd trimester | Associated with neonatal respiratory depression, withdrawal syndrome (irritability, hypertonia, tremors, feeding difficulties). Avoid prolonged use or high doses near term. |
Clinical note
Comprehensive clinical and safety monograph for ORAMORPH SR (ORAMORPH SR).
| Placental transfer | Extensive; morphine crosses the placenta readily, achieving fetal concentrations 60-100% of maternal levels. |
| Breastfeeding | Morphine is excreted into breast milk in low concentrations (0.09-0.61% of maternal dose). Monitor infant for drowsiness, respiratory depression, and feeding difficulties. Avoid in breastfeeding mothers who are ultra-rapid metabolizers of CYP2D6 (risk of toxicity). |
■ FDA Black Box Warning
["Addiction, Abuse, and Misuse: ORAMORPH SR exposes patients and other users to the risks of opioid addiction, abuse, and misuse, which can lead to overdose and death. Assess each patient's risk before prescribing.","Life-Threatening Respiratory Depression: Serious, life-threatening, or fatal respiratory depression may occur. Monitor for respiratory depression, especially during initiation or following a dose increase.","Accidental Ingestion: Accidental ingestion of even one dose of ORAMORPH SR, especially by children, can result in a fatal overdose of morphine.","Neonatal Opioid Withdrawal Syndrome: Prolonged use during pregnancy can result in neonatal opioid withdrawal syndrome, which may be life-threatening if not recognized and treated.","Cytochrome P450 3A4 Interaction: The concomitant use of ORAMORPH SR with all cytochrome P450 3A4 inhibitors may result in an increase in morphine plasma concentrations, which could increase or prolong adverse reactions and may cause potentially fatal respiratory depression. In addition, discontinuation of a concomitantly used cytochrome P450 3A4 inducer may result in an increase in morphine plasma concentration.","Risks from Concomitant Use with Benzodiazepines or Other CNS Depressants: Concomitant use of opioids with benzodiazepines or other central nervous system (CNS) depressants may result in profound sedation, respiratory depression, coma, and death."]
| Serious Effects |
Severe respiratory depressionAcute or severe bronchial asthmaKnown hypersensitivity to morphine or any componentParalytic ileusConcurrent use of monoamine oxidase inhibitors (MAOIs) or within 14 days of discontinuation
Loading safety data…
| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | First trimester: Limited human data, but animal studies show no teratogenicity at clinically relevant doses. Second and third trimesters: Chronic use may lead to fetal dependence and neonatal withdrawal syndrome (neonatal abstinence syndrome); use only if clearly needed. Risk of preterm labor and low birth weight with prolonged use. |
| Fetal Monitoring | Monitor maternal respiratory rate, sedation level, and oxygen saturation. Fetal monitoring includes non-stress test and biophysical profile as appropriate for gestational age. Assess for signs of neonatal withdrawal after delivery (e.g., Naloxone administration, Finnegan scoring). |
| Fertility Effects | Animal studies show no significant impairment of fertility at therapeutic doses. Human data limited; chronic opioid use may suppress ovulation and spermatogenesis due to hypothalamic-pituitary-gonadal axis suppression. |
| Precautions | Addiction, abuse, and misuse, Life-threatening respiratory depression, Accidental ingestion, Neonatal opioid withdrawal syndrome, Interaction with benzodiazepines and other CNS depressants, Chronic pulmonary disease: increased risk of respiratory depression, Head injury and increased intracranial pressure: may exacerbate effects, Hepatic or renal impairment: increased risk of toxicity, Hypotensive effects: caution in patients with circulatory shock, Gastrointestinal effects: may cause constipation; avoid in suspected paralytic ileus, Seizures: may aggravate seizure disorders, Biliary tract disease: may cause spasm of the sphincter of Oddi, Driving and operating machinery: may impair mental/physical abilities |
| Food/Dietary | Avoid alcohol; may potentiate CNS depression. No specific food restrictions, but high-fat meals may delay absorption. Maintain adequate fluid and fiber intake to prevent constipation. |
| Clinical Pearls | Oramorph SR is a sustained-release morphine formulation for chronic pain; do not crush or chew tablets. Onset is delayed; use immediate-release opioids for breakthrough pain. Equianalgesic dosing: 30 mg oral morphine ≈ 10 mg parenteral morphine. Monitor for respiratory depression, especially in opioid-naive patients. Avoid in patients with GI obstruction or acute asthma. Taper upon discontinuation to prevent withdrawal. |
| Patient Advice | Swallow tablets whole; do not crush, chew, or dissolve. · Take exactly as prescribed; do not increase dose without consulting doctor. · Avoid alcohol and other CNS depressants. · May cause drowsiness; avoid driving until you know how it affects you. · Store securely away from children and others; dispose of unused medication properly. · Common side effects: constipation, nausea, dizziness, drowsiness. · Contact doctor if you experience shallow breathing, severe drowsiness, or difficulty waking up. |