Cymbalta for Musculoskeletal Pain
Cymbalta (duloxetine hydrochloride) is a selective serotonin and norepinephrine reuptake inhibitor (SNRI). It is a prescription-only drug approved for the treatment of chronic musculoskeletal pain and chronic low back pain, which can be caused by conditions such as osteoarthritis. Cymbalta was first approved by the U.S. Food and Drug Administration (FDA) in 2004 for major depressive disorder. Subsequently, it was also approved for treatment of anxiety, pain caused by diabetic neuropathy, and pain caused by fibromyalgia before gaining FDA approval for chronic musculoskeletal pain in 2010.
Narcotic Analgesic
I. See Also
- Pharmacology: Metabolism of Opioids
- Codeine: Metabolizes to Hydrocodone and morphine
- Heroin: Metabolizes to 6-MAM and then to Morphine
- Morphine and Hydrocodone: metabolize to Hydromorphone
EQUIANALGESIC DOSING FOR MANAGEMENT OF ACUTE* OR CHRONIC PAIN
EQUIANALGESIC DOSING FOR MANAGEMENT OF ACUTE* OR CHRONIC PAIN
(Equivalent to Morphine 10mg IM/SC/IV)
Drug | IM/SC/IV (mg) | PO/PR/SL (mg) | Duration of Action (hrs) |
AGONISTS | |||
Morphine | 10 | 20-30 | 3-4 |
Codeine | 120-130 | 200 | 3-4 |
Hydromorphone | 2 | 4 | 3-4 |
Oxycodone | - | 15-20 | 3-4 |
Meperidine** | 75-100 | 300 | 3 |
Fentanyl | 100mcg (0.1mg) | - | 2-3 |
Fentanyl Transdermal | 25mcg/hr = 30- 66 mg IM/IV morphine/24hrs |
25mcg/hr = 60-134mg PO morphine/24hrs |
3 days |
Methadone | - | Depends on morphine dose (see below)** |
>6 |
* dose conversion is based on chronic pain management. May require lower IV doses for acute pain,
especially with IV bolus dosing
** not recommended for chronic pain management
- 2 x Tylenol #3 is approximately equivalent to 10mg PO morphine
- 2 x 292 is approximately equivalent to 10mg PO morphine.
- In round the clock administration of narcotics the IV/IM/SC routes are essentially equianalgesic.
- The oral, rectal, and sublingual routes are equianalgesic, if available
- Dosing frequency is usually based on the duration of action of the analgesic used; however,
certain individuals may obtain control with longer dosing intervals, and some patients may need
more frequent administration.
- Intravenous narcotics may have a shorter duration of action compared to other routes of administration.
**Daily chronic oral morphine equivalent |
Conversion ratio morphine:methadone |
< 100 mg |
3:1 |
100-300mg |
5:1 |
300-600mg |
10:1 |
600-800mg |
12:1 |
800-1000mg |
15:1 |
> 1000 mg |
20:1 |
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Opioid analgesic dose conversions
Opioid analgesic dose conversions
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Opioid analgesics are the cornerstone to treatment and control of severe pain. Equivalence of dose potency is not absolute and care must be taken in changing analgesics. In general, it is safer to use a lower regular dose with breakthrough analgesia rather than to convert immediately to the “equivalent” dose.
It is important nevertheless to know the approximately dosage conversions.
Equivalence to morphine 30 mg oral (1) | ||||||
Drug | Dosage | Ratio | ||||
morphine (subcutaneous) | 10 mg | 1:3 | ||||
morphine (intramuscular) | 6 mg | 1:5 | ||||
morphine (intravenous) (2) | 5 mg | 1:6 | ||||
oxycodone (oral) (3) | 15 mg | 1:2 | ||||
hydromorphone (oral) (4) | 6.5-7.5 mg | 1:4-5 | ||||
hydromorphone (subcutaneous/intramuscular) |
1.3-2.0 mg | 1:15-25 | ||||
fentanyl (transdermal patch) | 50 mcg/hr (*) | complex | ||||
codeine (oral) | 180 mg (**) | 6:1 | ||||
codeine (intramuscular) | 120 mg (**) | 4:1 | ||||
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Conversion to oral slow release formulations
Conversion to oral dosing is usually fairly simple.
DO:
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An example:
A patient has received morphine 5 mg subcutaneously q4-hourly regularly and in the past 24 hours, received an additional three 5 mg subcutaneous bolus breakthrough doses. To convert into and regimen of oral morphine:
(Step One): Calculate total dose over 24 hours
- regular doses: 5 mg x 6 doses = morphine 30 mg (s/c)
- bolus doses: 5 mg x 3 doses = morphine 15 mg (s/c)
- Total: morphine 45 mg (s/c) per 24 hours
(Step Two): Conversion to equivalent oral morphine
- subcutaneous morphine to oral morphine ~ 1:3
- Thus: 45 mg/day x 3
- Oral equivalent daily dose: morphine 135 mg (PO) per 24 hours
(Step Three): Split into divided doses
- Split dose (2 per day): morphine 135 mg (PO) / 2
- Thus: morphine SR 67.5 mg per dose twice daily
- Rounded down: morphine SR 60 mg (PO) twice daily
(Step Four): Breakthrough analgesia
- Regular dose: morphine SR 60 mg (PO) per 12 hours
- Breakthrough dose: (60 mg /12) x 50-100% = morphine 2.5-5.0 mg (PO) per hour
- Given that oral (short acting) morphine is given every fourth hourly: 2.5-5.0 mg/hr x 4 hr
- Breakthrough dose: morphine (immediate release) 10-20 mg (PO) q4-hourly PRN
Summary:
morphine SR 60 mg PO twice daily
+
morphine (imm. release) 10-20 mg PO q4-hourly PRN
After 24 hours, review the breakthrough (PRN) requirements. If a significant amount of breakthrough analgesia was required, this should be added to the regular analgesia.
Reference articles
(1) Examples of approximate equivalent doses when changing from morphine to another opioid (Table 10.7). Therapeutic guidelines: Analgesic, version 4, 2002.
(2) Morphine Sulfate Injection BP (DBL). MimsOnline. Last updated: 20 October 2005.
(3) OxyContin (oxycodone hydrochloride). MimsOnline. Last updated: 29 October 2004.
(4) Dilaudid (hydromorphone hydrochloride). MimsOnline. Last updated: 9 July 2004.
(5) Codeine Phosphate. MimsOnline. Last updated: 6 September 2001.