Hydromorphone

Information from VetDepot.com:

Major Uses

Hydromorphone is used in dogs and cats as a sedative, restraining agent, analgesic or preanesthetic. The drug is usually less sedating than morphine and rarely causes vasodilation and hypotension. However, there have been more incidences during testing of nausea and vomiting than with morphine.

Common Precautions

Hydromorphone is an opiate and should be used with caution in patients with hypothyroidism, Addison's disease, or severe renal insufficiency. Caution should also be used in geriatric or severely debilitated animals. Any animal that is suspected of gastric dilation, volvulus, or intestinal obstruction should be evaluated before taking hydromorphone due to the fact it may cause vomiting. Hydromorphone should be considered with extreme caution for animals with head injuries, increased intracranial pressure and acute abdominal conditions because of the possibility of the drug complicating the diagnosis or clinical course of these conditions.

Dogs have been noted to become sedated, whine, pant, become more vocal, vomit and defecate while taking hydromorphone. There is a possibility of dose related respiratory depression. A cat's body temperature can increase, which can last up to five hours. Hypothermia has been reported in cats, as well as bizarre behavioral changes. Hydromorphone can also cause bradycardia in the animals.

Hydromorphone should not be used in animals with a known allergy or hypersensitivity to the drug.

Storage

The injection and tablet form should be stored at room temperature in a light resistant container. The injection remains stable for at least 24 hours when mixed with IV fluids if protected from light. Suppositories need to be kept in the refrigerator.

Administration

Hydromorphone is available in oral, injectable and suppository form. After the drug is given to dogs, the peak levels occur between 10-30 minutes after dosing. Hydromorphone is five times more potent as an analgesic on a per weight basis when compared to morphine.

A typical dose of hydromorphone for dogs using an IV is 0.02-0.1 mg/kg, every two to four hours. When using an IM or SC injection, 0.05-0.2 mg/kg is used for every two to six hours. A typical dose for a cat using an IV, IM or SC injection is 0.05-0.1 mg/kg every two to six hours.

Doses may vary in different species, when the drug is given by a different route or concurrently with other medications, and with regards to a patient's age, breed, and health status. A veterinarian's dosing instructions and/or those printed on the medication label should be followed closely.

Information from Plumb's Veterinary Drug Handbook, 7th Edition, by Donald C. Plumb:

All opiates should be used with caution in patients with hypothyroidism, severe renal insufficiency (Addison's), and geriatric or severely debilitated patients. Hydromorphone is contraindicated in patients hypersensitive to narcotic analgesics, and those with diarrhea caused by a toxic ingestion (until the toxin is eliminated from the GI tract). Because it may cause vomiting, hydromorphone use should be considered contraindicated as a preanesthetic medication in animals with suspected gastric dilation, volvulus, or intestinal obstruction. Hydromorphone 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 or clinical course of these conditions. It should be used with extreme caution in patients sufferening from respiratory disease or acute respiratory dysfunction (e.g. pulmonary edema secondary to smoke inhalation). Hydromorphone can cause bradycardia and therefore should be used cautiously in patients with preexisting bradyarrythmias. Neonatal, debilitated, or geriatric patients may be more susceptible to the effects of hydromorphone and may require lower dosages. Patients with severe hepatic disease may have prolonged duration of action of the drug. Hyperthermia has been reported in cats with hydromorphone use and some recommend to avoid the use of this drug in cats. If used in cats at high dosages, the drug has been recommended to be given along with a tranquilizing agent, as hydromorphone alone can produce bizarre behavioral changes in this species. 

Hydromorphone has a similar adverse effect profile to oxymorphone or morphine in dogs and cats. In dogs, sedation, panting, whining, vocalization, vomiting, and defecation are often noted. Comiting, nausea, and defecation may occur more frequently with SC dosing versus IV dosing. CNS depression may be greater than desired, particularly when treating moderate to severe pain. In dogs, CRIs may cause sedation and adverse effects severe enough to require reducing the rate. Dose related respiratory depression is possible, and more likely during general anesthesia. Panting (may occur more often than with oxymorphone) and cough (suppressionmay be of benefit) may occur. Opioids can increase body temperature in cats. The increased body temperature is usually self-limiting and the majority return to normal within 5 hours, with no apparent morbidity or mortality. Administration of ketamine or isofluorance in addition to the hydromorphone did not produce a clinically relevant increase in body temperature compared with that of hydromorphone alone. Should hyperthermia occur, naloxone has been used to rapidly reduce body temperature in cats. Secondary to enhanced vagal tone, hydromorphone can cause bradycardia. Hydromorphone may cause histamine release that, while significantly less that with morphine and usually clinically insignificant, may be significant in critically ill animals. Constipation is possible with chronic dosing.

May have effects on fetus. Most opiates are excreted into milk, but effects on nursing offspring may not be significant. 

Massive overdoses may produce a profound reqspiratory and/or CNS depressionin most species. Other effects may include cardiovascular collapse, hypothermia, and skeletal muscle hypotonia. Mania may be seen in cats. 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's effects can diminish before sub-toxic levels of oxymorphone are attained. Mechanical respiratory support should be considered in cases of severe respiratory depression. In susceptible patients, moderate overdoses may require naloxone and supportive treatment as well. 

The following drugs may have interactions with hydromorphone: butorphanol, nalbuphine, other CNS depressants, diuretics, monoamine oxidase inhibitors, skeletal muscle relaxants, phenothiazines, tricyclic antidepressants, warfarin.