OXYMORPHONE HCL
Chemistry - A semi-synthetic phenanethrene narcotic agonist, oxymorphone HCl occurs asodorless white crystals or white to off-white powder. It will darken in color with prolonged exposure to light. One gram of oxymorphone HCl is soluble in 4 ml of water and it is sparingly soluble in alcohol and ether. The commercially available injection has a pH of 2.7 - 4.5.
Oxymorphone is approximately 10 times more potent an analgesic on a weight basis when compared to morphine. It has less antitussive activity than does morphine. In humans, it has more of atendency to cause increased nausea and vomiting than does morphine, while in dogs the oppositeappears to be true. At the usual doses employed, oxymorphone alone has good sedative qualities indog. Respiratory depression can occur especially in debilitated, neonatal or geriatric patients.
Bradycardia, as well as a slight decrease in cardiac contractility and blood pressure may also beseen. Like morphine, oxymorphone does initially increase the respiratory rate (panting in dogs)while actual oxygenation may be decreased and blood CO2 levels may increase by 10 mmHg ormore. Gut motility is decreased with resultant increases in stomach emptying times. Unlike eithermorphine or meperidine, oxymorphone does not appear to cause histamine release.
Although absorbed when given orally bioavailability is reduced, probably from a high first-passeffect. After IV administration, analgesic efficacy usually occurs within 3-5 minutes.
Like morphine, oxymorphone concentrates in the kidney, liver, and lungs; lower levels are found inthe CNS. Oxymorphone crosses the placenta and narcotized newborns can result if mothers aregiven the drug before giving birth, but these effects can be rapidly reversed with naloxone.
The drug is metabolized in the liver; primarily by glucuronidation. Because cats are deficient inthis metabolic pathway, half-lives in cats are probably prolonged. The glucuronidated metabolite isexcreted by the kidney.
It may also be used in swine as an adjunctive analgesic with ketamine/xylazine anesthesia and insmall rodents as an analgesic/anesthetic for minor surgical procedures.
Contraindications/Precautions - All opiates should be used with caution in patients with hypothyroidism, severe renal insufficiency, adrenocortical insufficiency (Addison's), and in geriatricor severely debilitated patients. Oxymorphone is contraindicated in patients hypersensitive tonarcotic analgesics, and in patients taking monamine oxidase inhibitors (MAOIs). It is alsocontraindicated in patients with diarrhea caused by a toxic ingestion until the toxin is eliminatedfrom the GI tract.
Oxymorphone should be used with extreme caution in patients with head injuries, increased intracranial pressure and acute abdominal conditions (e.g., colic) as it may obscure the diagnosis orclinical course of these conditions. It should be used with extreme caution in patients sufferingfrom respiratory disease or from acute respiratory dysfunction (e.g., pulmonary edema secondaryto smoke inhalation).
Oxymorphone can cause bradycardia and therefore should be used cautiously in patients withpreexisting bradyarrhythmias.
Neonatal, debilitated or geriatric patients may be more susceptible to the effects of oxymorphoneand may require lower dosages. Patients with severe hepatic disease may have prolonged durationsof action of the drug. If used in cats at high dosages, the drug has been recommended to be givenalong with a tranquilizing agent, as oxymorphone can produce bizarre behavioral changes in thisspecies. This also is true in cats also for the other opiate agents, such as morphine.
Opiate analgesics are also contraindicated in patients who have been stung by the scorpion species
Centruroides sculpturatus Ewing and C. gertschi Stahnke as it may potentiate these venoms.
Overdosage - Massive overdoses may produce profound respiratory and/or CNS depression inmost species. Other effects may include cardiovascular collapse, hypothermia, and skeletal musclehypotonia. Naloxone is the agent of choice in treating respiratory depression. In massive overdoses, naloxone doses may need to be repeated, and animals should be closely observed as naloxone'seffects may diminish before sub-toxic levels of oxymorphone are attained. Mechanical respiratorysupport should also be considered in cases of severe respiratory depression.
MOA inhibitors in humans. Some human patients have exhibited signs of opiate overdose afterreceiving therapeutic doses of oxymorphone while on these agents.
Laboratory Interactions - Plasma amylase and lipase values may be increased for up to 24hours following administration of opiate analgesics as they may increase biliary tract pressure.
Storage, Stability, Compatibility
The injection should be stored protected from light and atroom temperature (15-30° C); avoid freezing. The commercially available suppositories should bestored at temperatures between 2° and 15° C. Oxymorphone has been reported to be compatiblewhen mixed with acepromazine, atropine, and glycopyrrolate. It is incompatible when mixed withbarbiturates, and diazepam.Pharmacology - OXYMORPHONE HCL
See the monograph: Narcotic (Opiate) Analgesics for more infortmation.Oxymorphone is approximately 10 times more potent an analgesic on a weight basis when compared to morphine. It has less antitussive activity than does morphine. In humans, it has more of atendency to cause increased nausea and vomiting than does morphine, while in dogs the oppositeappears to be true. At the usual doses employed, oxymorphone alone has good sedative qualities indog. Respiratory depression can occur especially in debilitated, neonatal or geriatric patients.
Bradycardia, as well as a slight decrease in cardiac contractility and blood pressure may also beseen. Like morphine, oxymorphone does initially increase the respiratory rate (panting in dogs)while actual oxygenation may be decreased and blood CO2 levels may increase by 10 mmHg ormore. Gut motility is decreased with resultant increases in stomach emptying times. Unlike eithermorphine or meperidine, oxymorphone does not appear to cause histamine release.
Pharmacokinetics - OXYMORPHONE HCL
Oxymorphone is absorbed when given by IV, IM , SQ, and rectal routes.Although absorbed when given orally bioavailability is reduced, probably from a high first-passeffect. After IV administration, analgesic efficacy usually occurs within 3-5 minutes.
Like morphine, oxymorphone concentrates in the kidney, liver, and lungs; lower levels are found inthe CNS. Oxymorphone crosses the placenta and narcotized newborns can result if mothers aregiven the drug before giving birth, but these effects can be rapidly reversed with naloxone.
The drug is metabolized in the liver; primarily by glucuronidation. Because cats are deficient inthis metabolic pathway, half-lives in cats are probably prolonged. The glucuronidated metabolite isexcreted by the kidney.
Uses, Indications
Oxymorphone is used in dogs and cats as a sedative/restraining agent, analgesic and preanesthetic and occassionally in horses as an analgesic and anesthesia induction agent.It may also be used in swine as an adjunctive analgesic with ketamine/xylazine anesthesia and insmall rodents as an analgesic/anesthetic for minor surgical procedures.
Contraindications/Precautions - All opiates should be used with caution in patients with hypothyroidism, severe renal insufficiency, adrenocortical insufficiency (Addison's), and in geriatricor severely debilitated patients. Oxymorphone is contraindicated in patients hypersensitive tonarcotic analgesics, and in patients taking monamine oxidase inhibitors (MAOIs). It is alsocontraindicated in patients with diarrhea caused by a toxic ingestion until the toxin is eliminatedfrom the GI tract.
Oxymorphone should be used with extreme caution in patients with head injuries, increased intracranial pressure and acute abdominal conditions (e.g., colic) as it may obscure the diagnosis orclinical course of these conditions. It should be used with extreme caution in patients sufferingfrom respiratory disease or from acute respiratory dysfunction (e.g., pulmonary edema secondaryto smoke inhalation).
Oxymorphone can cause bradycardia and therefore should be used cautiously in patients withpreexisting bradyarrhythmias.
Neonatal, debilitated or geriatric patients may be more susceptible to the effects of oxymorphoneand may require lower dosages. Patients with severe hepatic disease may have prolonged durationsof action of the drug. If used in cats at high dosages, the drug has been recommended to be givenalong with a tranquilizing agent, as oxymorphone can produce bizarre behavioral changes in thisspecies. This also is true in cats also for the other opiate agents, such as morphine.
Opiate analgesics are also contraindicated in patients who have been stung by the scorpion species
Centruroides sculpturatus Ewing and C. gertschi Stahnke as it may potentiate these venoms.
Adverse Effects, Warnings
Oxymorphone may cause respiratory depression and bradycardia(see above). When used in cats at high dosages, oxymorphone may cause ataxia, hyperesthesia andbehavioral changes (without concomitant tranquilization). Decreased GI motility with resultantconstipation has also been described.Overdosage - Massive overdoses may produce profound respiratory and/or CNS depression inmost species. Other effects may include cardiovascular collapse, hypothermia, and skeletal musclehypotonia. Naloxone is the agent of choice in treating respiratory depression. In massive overdoses, naloxone doses may need to be repeated, and animals should be closely observed as naloxone'seffects may diminish before sub-toxic levels of oxymorphone are attained. Mechanical respiratorysupport should also be considered in cases of severe respiratory depression.
Drug Interactions
Other CNS depressants (e.g., anesthetic agents, antihistamines, phenothiazines, barbiturates, tranquilizers, alcohol, etc.) may cause increased CNS or respiratory depressionwhen used with oxymorphone. Oxymorphone is contraindicated in patients receiving monoamineoxidase (MOA) inhibitors (rarely used in veterinary medicine) for at least 14 days after receivingMOA inhibitors in humans. Some human patients have exhibited signs of opiate overdose afterreceiving therapeutic doses of oxymorphone while on these agents.
Laboratory Interactions - Plasma amylase and lipase values may be increased for up to 24hours following administration of opiate analgesics as they may increase biliary tract pressure.