Butorphanol Tartrate

(butorphanol tartrate)

Brands

Veterinary: Torbutrol, Torbugesic

Veterinary Availability:

Torbutrol tablets: 1 mg, 5 mg, 10 mg
Suspension: variety of strengths can be obtained from compounding pharmacies, online, through prescription from veterinarian (e.g., Wedgewood Pharmacy, based in New Jersey: https://www.wedgewoodpharmacy.com/items/pimobendan-oral-suspension.html).
Torbutrol injectable: 0.5 mg/mL in 10 mL vials
Torbugesic injectable: 10 mg/mL in 50 mL vials

Brands

Human: Stadol

Human Availability:

Stadol injectable: 1 mg/mL, 2 mg/mL

Pharmacology

Butorphanol is a synthetic partial opiate agonist that is structurally related to Morphine. It is a more potent analgesic than Morphine, but unlike Morphine it possesses less cardiovascular effects, and respiratory center sensitivity.

Its actions are similar to that of other partial agonists such as, pentazocine or nalbuphine. The agonist activity of butorphanol is believed to be exerted at the kappa and sigma receptors.

Butorphanol binds to opiate receptors at sites in the central nervous system and alters perception and response to pain. It also has the ability to act as an antitussive.

Duration of action following dose appears to be 4 hours.

It is absorbed in the gut with its highest distribution levels being in the kidney, liver, and intestine. Levels throughout other tissues are found to be higher than plasma. The drug is metabolized in the liver, crosses placental barrier, and distributed into breast milk. It is excreted in urine and bile and eliminated in the feces.

Safety in pregnant and very young animals has not been determined.

Indications

Used as an analgesic and a sedative.

Drug Interactions or Contraindications

Incompatible mixed with dimenhydrinate and pentobarbital sodium.
Use cautiously in hypothyroidism, severe renal insufficiency, or severely debilitated.
Butorphanol, if used with other central nervous system depressants may increase the CNS or respiratory depression of those drugs. It is recommended to decrease butorphanol’s dosage if used in conjunction with those particular drugs.

Adverse Reactions

CNS: sedation, confusion, lethargy, agitation.

CV: bradycardia

Resp: decreased respiratory rate

GI: constipation

GU: urinary retention

Skin: itching

Other:

*Note:In the event there are signs of overdose such as cardiac and respiratory depression administer the following:

naloxone 0.01 to 0.10 mg/kg SC, IP (narcotic reversal) ¹^, ³⁴^, ⁴¹^, ⁴²
fluids
O2
vasopressors

Dosage Recommendations

0.2 mg/kg to 2 mg/kg, q2hr to q4hr ³⁵^, ⁴¹^,  ⁴⁴

or

1 mg/kg to 2 mg/kg, SQ, q4hr ⁴¹^,  ⁴⁴

or

0.5 mg/kg to 2 mg/kg, SQ, q6hr ²

or

1 mg/kg to 5 mg/kg, SQ, q2hr to q4hr (Sedation) ¹

or

1 mg/kg to 5 mg/kg, SQ, q4hr ²⁶^,  ³⁴^, ⁴¹^, ⁴²^,  ⁴⁴

or

0.18 mg/lb to 10 mg/lb SQ, or 1 mg/lb , PO, q4hr to q6hr ³^, ¹²

or

0.25 mg/lb to 1 mg/lb, SQ (effective for pain) ³, ¹²

or

When combined with diazepam: 0.25 mg/lb butorphanol and 1 mg/lb diazepam. ³^, ¹²

Considerations

Note to veterinarians: the chance of rats developing pica following the use of butorphanol may be less than it is with buprenorphine due to butorphanol’s short duration of action.

However, it is advised to instruct pet owners to monitor for this behavior if an opioid medication is given, and to contact vet immediately. Also have the pet owner remove the rat from any bedding source that might be chewed and ingested until medication has passed through the system.

It is also important to be aware that pica may be observed, in rats, where pain has not been adequately addressed.
Store drug at room temperature away from light.

References

Anesthesia and Analgesia in Laboratory Animals at UCSF. (2018, April). Retrieved September 5, 2020, from https://larc.ucsf.edu/veterinary-information.
Takeda, N., Hasegawa, S., Morita, M., & Matsunaga, T. (1993). Pica in rats is analogous to emesis: an animal model in emesis research. Pharmacology, biochemistry, and behavior, 45(4), 817–821. https://doi.org/10.1016/0091-3057(93)90126-e