Inclusion Criteria:
* Normal healthy adult subjects between 20-40 years of age.
* Body weight within 80-120% of ideal body weight. Ideal body weight = (height-80)0.7
* Acceptable medical history and physical examination including:
* Normal chest X-ray and ECG results within six months prior to Period I dosing.
* No particular clinical significance in general disease history within two months prior to Period I dosing.
* Acceptable clinical laboratory determinations without significant deviation from normal values within two months prior to Period I dosing, which includes:
* AST (SGOT)
* ALT (SGPT)
* Gama-GT
* alkaline phosphatase
* total bilirubin
* albumin
* glucose
* BUN
* uric acid
* creatinine
* total cholesterol
* triglyceride(TG)
* Acceptable hematology within two months prior to the study, which includes hemoglobin, hematocrit, red blood cells, MCV, MCH, MCHC, white blood cells, differential white blood cells and platelets.
* Acceptable urinalysis within two months prior to the study, which includes pH, blood, glucose and protein.
* Signed the written informed consent to participate in this study.
Exclusion Criteria:
* Recent history of drug or alcohol addiction or abuse.
* A clinically significant disorder involving the cardiovascular, respiratory, renal, gastrointestinal, immunologic, hematologic, endocrine or neurologic system(s) or psychiatric disease (as determined by the clinical investigator).
* History of allergic response(s) to nalbuphine or related drugs.
* History of clinically significant allergies including drug allergies or allergic bronchial asthma.
* Evidence of chronic or acute infectious diseases.
* Any clinically significant illness or surgery during the four weeks prior to Period I dosing (as determined by the clinical investigator).
* Taking any drug known to induce or inhibit hepatic drug metabolism within one month prior to the beginning of the study.
* Receiving any investigational drug within one month prior to Period I dosing.
* Taking any prescription medication or any nonprescription medication within two weeks prior to Period I doing.
* Donating greater than 150 ml of blood within two months prior to Period I dosing or donating plasma (e.g., plasmapheresis) within 14 days prior to Period I dosing. All subjects will be advised not to donate blood for four weeks after completing the study.
* Consumption of caffeine, xanthine-containing products (i.e., coffee, tea, caffeine-containing sodas, colas and chocolate, etc.) and/or alcohol at least 48 hours prior to days on which dosing is scheduled and during the periods when blood samples are being collected.
* Any other medical reason as determined by the clinical investigator.
* Patient is pregnant or breastfeeding. Women of childbearing potential must have a negative urine pregnancy test at Baseline.