Hydromorphone, a Schedule II semi-synthetic opiate, possesses a structure similar to that of morphine, which makes it part of phenanthrenes group1. Additionally, this drug is a µ receptor agonist and is 7-10 times more potent than morphine2. It is prescribed as an analgesic for moderate to moderately severe pain under the following trade names: Dilaudid, Exalgo and Palladone. Hydromorphone is widely prescribed with approximately 3.9 million prescriptions in 2012 and 972,000 in the first quarter of 2013.
Hydromorphone is administered orally via a tablet with typical doses of 2-8 mg. An extended release formulation is available, for patients who require around the clock pain relief, in tablet or capsule form with a dose of 8-32 mg. Furthermore, hydromorphone may be administered intravenously, subcutaneously or intramuscularly with typical doses ranging from 1-10 mg5.
Following an 8 mg oral dose of hydromorphone, peak plasma concentrations occurred around 0.8 hours with a half-life of 3-9 hours. Following a single extended release dose of 32 mg, peak plasma concentrations occurred around 16 hours with a half-life of 10-22 hours5.
Hydromorphone is extensively metabolized via glucuronidation in the liver, with greater than 95% of the dose metabolized to hydromorphone-3-glucuronide along with minor amounts of 6-hydroxy reduction metabolites2,5.
Approximately 6% of parent drug, 36% of conjugated hydromorphone, and traces of minor metabolites are excreted in the 24 hour urine5.
For qualitative screening purposes, hydromorphone will significantly cross-react with the opiate Enzyme Immunoassay (EIA) at the 300 ng/mL cutoff 6. Ultra-Performance Liquid Chromatography-Tandem Mass Spectrometry (UPLC-MS/MS) is used to confirm and quantify hydromorphone, with a cutoff concentration of 20 ng/mL. The urine samples are hydrolyzed prior to analysis and the total hydromorphone concentration is reported.
The interpretation of patients prescribed hydromorphone should be conducted with caution since it is a prescription drug and a metabolite of hydrocodone. Patients prescribed only hydromorphone should not have hydrocodone in their urine. However, hydromorphone preparations may contain morphine and hydrocodone as impurities up to 0.025 % and hydromorphone is a known impurity in oxymorphone preparations up to 0.1 %8. Also, in a study conducted by Coneet al, patients chronically administered morphine had low concentrations of hydromorphone present7. Therefore, if other opiates are present in the urine at low concentrations in addition to hydromorphone, clinical interpretations should include the entire medical history of the patient and known contaminants in the medication.