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BackMorphine Data - Uses, Dosage, Drug class, Brand name, Warnings, etc
| Pharmacology | Morphine and other opioids interact with stereospecific opiate receptors in the CNS and other tissues. Morphine, a mu opioid agonist, inhibits nociceptive reflexes by reducing neurotransmitter release, inhibits neurons conveying nociceptive information to higher brain centers, and enhances activity in descending inhibitory pathways in the spinal cord. Mu receptors mediate analgesia, respiratory depression, miosis, decreased GI motility, and euphoria. Kappa receptors cause analgesia, less intense miosis, respiratory depression, dysphoria, and psychotomimetic effects. The role of delta receptors in humans is unclear. Pain relief is specific, leaving other sensory modalities and mental processes largely unaffected, except in large doses or opioid-naive patients. Morphine also has antitussive effects at lower doses than required for analgesia. |
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| Administration and Adult Dosage |
No ceiling dose for morphine (except transdermal fentanyl); very large doses may be required for severe pain: - PO for analgesia: 8–20 mg every 4 hr - SR Tablet (12-hr): • Narcotic-naive: 30 mg every 8–12 hr initially • Narcotic-tolerant: Total daily oral morphine equivalent in 2 divided doses every 12 hr - SR Capsule (24-hr): • Narcotic-naive: 20 mg every 24 hr initially • Narcotic-tolerant: Total daily oral morphine equivalent every 24 hr - SC for analgesia: 5–15 mg every 4 hr (10 mg/70 kg optimal initial dose) - PR for analgesia: 10–20 mg every 4 hr - IV for analgesia: 4–10 mg, dilute and inject slowly over 2–3 min - IV infusion: 1–10 mg/hr; up to 95 mg/hr for chronic pain - IV PCA: 1 mg per activation initially, 5–20 min lockout, titrated to response - Epidural (unpreserved solution): • Intermittent: 5 mg initially, may repeat with 1–2 mg after 1 hr • Continuous infusion: 0.05–0.1 mg/kg loading dose, then 0.005–0.01 mg/kg/hr - IT for cancer pain (unpreserved): 0.4–8.3 mg/day (average 1–23 mg/day) - IT for cesarean section (unpreserved): 0.1 mg - Intraventricular (unpreserved): 0.1–2 mg, repeated ~every 24 hr - Inhalation for dyspnea: 5–15 mg in 2 mL sterile water or NS via nebulizer every 4 hr - IM administration not recommended due to pain |
| Special Populations - Pediatric Dosage |
- PO: 0.3 mg/kg every 3–4 hr - IV: 0.05–0.2 mg/kg every 4 hr - IV infusion: 0.01–0.04 mg/kg/hr - Epidural: 0.05–0.08 mg/kg - IT: 0.01–0.03 mg/kg |
| Special Populations - Geriatric Dosage | Reduce initial dosage; use smaller incremental increases (~25%) in total daily dosage compared to younger patients. |
| Other Conditions | Reduce initial dosage in debilitated patients. |
| Dosage Forms |
- Capsule: 15, 30 mg - Solution: 2, 4, 20 mg/mL - Suppository: 5, 10, 20, 30 mg - Tablet: 10, 15, 30 mg - Sustained-Release Tablet (8, 12 hr): 15, 30, 60, 100, 200 mg - Sustained-Release Capsule (24 hr): 20, 50, 100 mg - Injection (unpreserved): 0.5, 1, 10, 25, 50 mg/mL - Injection (preserved): 2, 3, 4, 5, 8, 10, 15, 25, 50 mg/mL |
| Patient Instructions |
- Take as directed; do not exceed recommended dosage - May cause drowsiness; avoid driving or operating machinery until effects are known - Avoid alcohol and other CNS depressants - Report severe constipation, difficulty breathing, or confusion to your physician |
| Missed Doses |
- If taken on a regular schedule, take a missed dose as soon as remembered - If near the time for the next dose, take that dose only; do not double the dose or take extra |
| Pharmacokinetics - Onset and Duration | - Analgesia (IM): Onset 10–30 min; peak 0.5–1 hr; duration 3–5 hr |
| Pharmacokinetics - Serum Levels | - Moderate analgesia: ~50 µg/L (88 nmol/L) |
| Pharmacokinetics - Fate |
- Bioavailability: Oral 24 ± 12% due to extensive first-pass conjugation; nebulized 5 ± 3%, peak at 10 min - Peak Levels (10 mg IM): ~56 µg/L (98 nmol/L) within 20 min - Protein Binding: 35 ± 2%; decreased in acute viral hepatitis, cirrhosis, hypoalbuminemia - Distribution: Vd = 2.12 L/kg (young normals), 1.16 L/kg (elderly) - Clearance: Cl = 2.02 L/hr/kg (young normals), 1.66 L/hr/kg (elderly); adult levels by 6 months–2.5 yr - Metabolism: Hepatic conjugation to morphine-6-glucuronide (active) and morphine-3-glucuronide (inactive/antagonistic) - Excretion: Mostly urinary; 14 ± 7% as morphine-6-glucuronide, 3.4% (oral) to 9% (parenteral) unchanged - Higher morphine-6-glucuronide levels with oral vs. parenteral administration; reduced clearance in renal insufficiency |
| Pharmacokinetics - t¹⁄₂ | - Elimination half-life: 1.9 ± 0.5 hr; increased in neonates and premature infants |
| Adverse Reactions & Side Effects |
Major: - Respiratory depression, circulatory depression, constipation Frequent: - Sedation, dizziness, nausea, vomiting, sweating Occasional: - Euphoria, dysphoria, dry mouth, biliary tract spasm, postural hypotension, syncope, tachy-/bradycardia, urinary retention, myoclonus (dose-related, especially IV/intraspinal) Epidural-specific: - Urinary retention, pruritus (manageable with naloxone or butorphanol) Rare: - Allergic-type reactions (skin rash, wheal/flare with IV, due to histamine release, not true allergy) - Confusion/disorientation (linked to phenol/formaldehyde preservatives in epidural infusions) - Seizures (high-dose IV with sodium bisulfite) - Increased adverse reaction risk in renal failure |
| Contraindications | - Hypersensitivity to morphine or other opioids |
| Precautions & Warnings |
- Use caution with CNS depressants, pregnancy, head injury, intracranial lesions, increased intracranial pressure, acute asthma, COPD, cor pulmonale, decreased respiratory reserve, hypoxia, hypercapnia, compromised blood pressure, atrial flutter/supraventricular tachycardias, prostatic hypertrophy, urethral stricture, elderly/debilitated patients, acute abdominal pain (may obscure diagnosis), renal dysfunction, elevated bilirubin/LDH - Infants >1 month eliminate morphine efficiently but may need longer dosing intervals - Do not administer IV, IT, or epidurally to opioid-naive patients without narcotic antagonist and respiratory support available |
| Drug Interactions |
- CNS depressants (e.g., alcohol, antipsychotics, anesthetics, antidepressants, sedative-hypnotics) increase respiratory depression risk - Cimetidine increases opioid serum concentration and duration of effect |
| Parameters to Monitor | - Monitor pain control, respiratory, and cardiovascular depression signs |
| Class and Drug Brand Name |
- Class: Opioids - Brand Name: Various |
| Notes |
- Myoclonus can be managed by switching opioids or using benzodiazepines/dantrolene - Continuous infusion with PCA effective for chronic cancer pain - Inhalation useful for dyspnea management |
References
Hand of Clinical Drug Data