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| Names | |
|---|---|
| Pronunciation | bue tor’ fa nol[1] |
| Trade names | Stadol, others |
| Other names | BC 2627 |
| |
| Clinical data | |
| Drug class | Opioidagonist–antagonist[1] |
| Main uses | Moderate to severe pain[1] |
| Side effects | Sleepiness,respiratory depression, confusion,feeling high, agitation, itchiness, sweating, nausea,constipation[1] |
| Pregnancy category |
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| Routes of use | IV, intranasal |
| Onset of action | Within 15 min[2] |
| Duration of action | Up to 5 hrs[2] |
| Typical dose | 1 to 2 mg[2] |
| External links | |
| AHFS/Drugs.com | Monograph |
| MedlinePlus | a682667 |
| Legal | |
| Legal status |
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| Pharmacokinetics | |
| Bioavailability | Nasal: 60-70%; Sublingual: 25%-35%; PO 10% |
| Metabolism | Liver hydroxylated &glucuronidated |
| Eliminationhalf-life | 4-7 hours |
| Excretion | Kidney, 75% Biliary, 11-14% Fecal, 15% |
| Chemical and physical data | |
| Formula | C21H29NO2 |
| Molar mass | 327.468 g·mol−1 |
| 3D model (JSmol) | |
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Butorphanol, sold under the brand nameStadol among others, is anopioid used to treat pain.[1] As anasal spray, it may be used to treatmigraines.[1] By injection into a vein or muscle, it may be used to treat moderate to severe pain.[1][2] Onset of effects is within 15 minutes and may last up to 5 hours.[2]
Side effects may include sleepiness,respiratory depression, confusion,feeling high, agitation, itchiness, sweating, nausea, andconstipation.[1] While there is the potential for misuse, this is less thanmorphine.[1] Long term use in pregnancy can result inneonatal abstinence syndrome in the baby.[3] It hasagonist–antagonist effects at the µ and ĸ typeopiate receptors.[1]
Butorphanol was patented in 1971 and approved for medical use in 1978.[4][1] It is available as ageneric medication.[1] In the United States a 1 mg vial for injection costs about 6 USD.[5] In the United States it is aschedule IV controlled substance.[1]
The most common indication for butorphanol is management ofmigraine using the intranasal spray formulation. It may also be usedparenterally for management of moderate-to-severe pain, as a supplement for balanced generalanesthesia, and management of pain duringlabor. Butorphanol is also quite effective at reducing post-operative shivering (owing to its Kappa agonist activity). Butorphanol is more effective in reducing pain in women than in men.[6]
It may be used at a dose of 1 mg IV or IN.[2] IM injections may be 2 mg.[2]
As with other opioid analgesics, central nervous system effects (such assedation,confusion, anddizziness) are considerations with butorphanol.Nausea andvomiting are common. Less common are the gastrointestinal effects of other opioids (mostly constipation). Another side effect experienced by people taking the medication is increased perspiration.
Butorphanol exhibitspartial agonist andantagonist activity at theμ-opioid receptor, as well as partial agonist activity at theκ-opioid receptor (Ki = 2.5 nM;EC50 = 57 nM;Emax = 57%).[6][7] Stimulation of these receptors oncentral nervous systemneurons causes an intracellularinhibition ofadenylate cyclase, closing of influx membranecalcium channels, and opening of membranepotassium channels. This leads to hyperpolarization of the cellmembrane potential and suppression of action potential transmission of ascending pain pathways.Because of its κ-agonist activity, at analgesic doses butorphanol increases pulmonary arterial pressure and cardiac work. Additionally, κ-agonism can causedysphoria at therapeutic or supertherapeutic doses; this gives butorphanol a lower potential for abuse than other opioid drugs.[8]
Within theINN,USAN,BAN, andAAN naming systems this drug is known asbutorphanol, while withinJAN it is namedtorbugesic.[9][10][11] As thetartratesalt, butorphanol is known asbutorphanol tartrate (USAN,BAN).[9][10][11]
Its tradenameStadol was recently discontinued by the manufacturer. It is now only available in its generic formulations manufactured byApotex,Mylan, Novex and Ben Venue Laboratories.
Butorphanol is available in the U.S. as ageneric drug; it is available in various nations under one of any number of trade names, including Moradol and Beforal (Brand name Stadol no longer available in the US); veterinary trade names include Butorphic, Dolorex, Morphasol, Torbugesic, and Torbutrol.
Butorphanol is listed under theSingle Convention on Narcotic Drugs 1961 and in the United States is a Schedule IV Narcotic controlled substance with a DEA ACSCN of 9720; being in Schedule IV it is not subject to annual aggregate manufacturing quotas. The free base conversion ratio of the hydrochloride is 0.69.[12] Butorphanol was originally in Schedule II and at one point it was decontrolled.
Inveterinary anesthesia, butorphanol (trade name: Torbugesic) is widely used as asedative and analgesic in dogs, cats and horses. For sedation, it may be combined with tranquilizers such as alpha-2 agonists (medetomidine), benzodiazepines, oracepromazine in dogs, cats and exotic animals. It is frequently combined withxylazine ordetomidine in horses.[13]
Butorphanol is frequently used for post-operative and accident-related pain in small mammals such as dogs, cats, ferrets, coatis, raccoons, mongooses, various marsupials, some rodents and perhaps some larger birds, both in the operating suite and as a regular prescription medication for home use, for management of moderate to severe pain.
Although butorphanol is commonly used for pain relief in reptiles, no studies (as of 2014) have conclusively shown that is an effective analgesic in reptiles.[14]
Butorphanol is a commonly used narcotic for pain relief in horses. It is administered either IM or IV, with its analgesic properties beginning to take effect about 15 minutes after injection and lasting 4 hours. It is also commonly paired with sedatives, such asxylazine anddetomidine, to make the horse easier to handle during veterinary procedures.
Side effects specific to horses include sedation, CNS excitement (displayed byhead pressing or tossing). Overdosing may result in seizures, falling, salivation, constipation, and muscle twitching. If an overdose occurs, a narcotic antagonist, such asnaloxone, may be given. Caution should be used if butorphanol is administered in addition to other narcotics, sedatives, depressants, or antihistamines as it will cause an additive effect.
Butorphanol can cross the placenta, and it will be present in the milk of lactating mares who are given the drug.
The drug is also prohibited for use in competition by most equestrian organizations, including theFEI, which considers it a class A drug.
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