Pain Management
MORPHINE: DRUG FACTS
What preparations are available?
Immediate Release(IR): suppositories (5,10,20,30 mg); tablets (5,10,15mg);
liquids (1mg/ml, 2 mg/ml, 20 mg/ml);
Sustained Release(SR): tablets (MS Contin, Oramorph) (15,30,60,100, 200 mg)
Parenteral Solutions(IR): preserved solutions (1,10,15 mg/ml);
preservative free solutions (1 mg/ml; 25 mg/ml)
How is it used?
Oral (PO): route of choice; 30mg=10mg IM in repeated doses because first pass effect of hepatic metabolism (portal circulation from the gut goes to liver where part of the dose is metabolized); immediate release preparations are effective for breakthrough pain to titrate doses and for acute pain; often less expensive and allows for mobility and independence; sustained release tablets are useful when 24 hour dose is known and to decrease the number of times per day that pills are taken.
Rectal (PR): 30mg=10mg IM; circulation to the rectum may be either portal or systemic-if using MS Contin per rectum (off label use), decrease initial dose to 1/3 oral dose and rapidly titrate to effect (prevents overdose if rectal circulation is predominately systemic); useful when swallowing is compromised or with severe nausea and vomiting.
Sublingual (SL): Has poor absorption and bitter taste; use not advised.
Subcutaneous (SC): 10mg SC=10mg IM; drug concentration limited to 60 mg/ml (not soluble at higher doses); infuse at no greater than 2 ml/hr/infusion site; use of preservative-free solutions is recommended for high dose infusions (causes sedation); may be easier route for families to maintain than IV.
Intramuscular (IM): 10mg is equalizing dose for other opioids.
Intravenous (IV): 5mg IV=10mg IM for bolus doses, 10mg IV=10mg IM for continuous infusions; use of preservative-free solutions is recommended for high dose infusions (preservatives may cause sedation).
Epidural (Epi): 10mg Epi=60mg/24 hr IM; use of preservative-free solutions is recommended (preservatives may cause neural damage).
Intrathecal (IT): 1mg IT=60mg/24 hr IM; use of preservative-free solutions is recommended (preservatives may cause neural damage).
When should it be used?
PO: first choice drug when the GI tract is functioning.
PR: po not possible.
SC, IM, IV Bolus: rapid pain relief is required.
SC, IV Infusion: rapid pain relief is required and PO not possible; excessive sedation with PO (especially SC); for limited IV access, SC easy for family.
Epidural: PO/SC/IM/IV not possible; excessive sedation with other routes.
Intrathecal: PO/SC/IM/IV not possible; excessive sedation with other routes; smaller dose needed because the epidural concentration limit of morphine has been reached.
When should it not be used?
PO: vomiting, dysphagia, bowel obstruction, altered absorption.
PR: severe diarrhea.
SC, IM, IV Bolus: thrombocytopenia.
SC, IV Infusion: as first choice route when po route available.
Epidural: septicemia, thrombocytopenia.
Intrathecal: septicemia, thrombocytopenia.
What are the common side effects?
PO/PR/SC/IM/IV: constipation, sedation, nausea and vomiting.
SCInfusion: erythema at injection site (use dexamethasone in solution).
Epidural: constipation, sedation, nausea and vomiting, itching, myoclonus.
Intrathecal: nausea and vomiting, constipation, itching, myoclonus.
What doses have been used and are possible to use?
PO/PR: 35,000 mg/day.
IV: 1,564 mg/hr.
Intrathecal: 200 mg/day.
*** Special Note *** There is no ceiling or maximum dose that can be given!! As dose is increased and increased pain relief occurs, tolerance develops to all side effects, except constipation.
When does it start to work (onset)? When is the most effective level (peak)? How long does it work (duration)?
Morphine: / Onset / Peak / DurationIRPO: / 30 min / 1-2 hr / 4-5 hr
SR PO: / 30-45 min / 3.5 hr / 8-12 hr
PR: / 30 min / 1-2 hr / 4-5 hr
SC Bolus: / 10-30 min / 50-90 min / 4-5 hr
IM: / 10-30 min / 30-60 min / 4-5 hr
IV Bolus: / 5 min / 20 min / 2-4 hr
Epidural: / 15-60 min / Up to 24 hr
Intrathecal: / 15-60 min / Up to 24 hr
When should it be titrated?
Titrate upward when pain relief goal is not achieved until there are dose limiting side effects (excessive side effects). Titrate downward when the patient's pain relief goal is achieved but patient is somnolent.
How is it titrated?
For immediate release PO or PR morphine, increase the 24 hour dose based on amount of morphine required to "rescue" the patient from breakthrough pain and increase the rescue dose to 5-10% of the new 24 hour dose. For parenteral infusions, the loading dose should be equal to the mg/hr dose. Increases the mg/hr by 10% to 20% if pain is not relieved. To withdraw from morphine, decrease the 24 hour dose by 50% and give 25% of this dose every 6 hours; after 2 days, reduce daily dose by an additional 25% every 2 days until 24 hour dose is 30mg PO per day, then discontinue the morphine.
When should it be changed to another route?
Oral is the preferred route. The slow onset of action makes the oral route less effective when control of rapidly changing pain is needed; the IV route is better for this type of pain. SC infusions have been associated with less nausea than oral morphine. Epidural or intrathecal morphine may be indicated when sedation is a dose limiting side effect.
How should it be changed to another route?
Calculate the total 24 hour dose, convert to equianalgesic dose for new route. Administer appropriate fraction of 24 hour dose for new route. For example, 180mg MS Contin every 12 hours plus 80mg IR MS for breakthrough pain=440mg PO MS/24 hr. From the equianalgesic conversion chart, 10mg IM=30mg PO MS. Therefore, to start a continuous SC infusion,
440mg divided by 3=147 IM MS equivalents; 147mg/24 hr=6mg/hr.
When should it be changed to another drug?
When dose limiting side effects occur, changing to another agonist (e.g., Dilaudid, methadone, fentanyl) may improve analgesia and should be considered before progressing to a more invasive route. Favorable prior experience with another drug may be an important reason to change to another drug.
How should it be changed to another drug?
Calculate the 24 hr dose, convert to equianalgesic dose for the new drug. For example, 180mg MS Contin every 12 hours plus 80mg IR MS for breakthrough pain=440mg PO MS/24 hr. Using the conversion chart, 7.5mg PO Dilaudid = 30mg PO MS. Thus, 440mg/30mg equals
?mg/7.5mg=110mg 24 hr Dilaudid; 110mg/6 doses per 24 hr=18mg q 4 hr. Experts recommend that 2/3 of this dose be administered to compensate for the lack of cross-tolerance between morphine and hydromorphone: 110 x .66=72.6mg/6 doses per 24 hr=12mg q 4 hr. If this dose is insufficient to relieve pain, escalate it to the original 18mg q 4 hr. Titrate upward as needed to relieve pain.