Introduction 
    Pain is one of the most common clinical signs, and is listed as the fifth vital sign after respiration, body temperature, pulse, and blood pressure. Severe pain caused by acute trauma, surgery, and chronic and recurrent diseases has become an unbearable burden to the body.

    Pain includes the sensation produced when the body is damaged, and the response the body reacts to damage. Pain can be a warning that the body is being injured to induce a series of defensive protective mechanisms. However, warning has its limits; certain types of chronic severe pain are unbearable.

    Indications 
    Indication approved by Taiwan FDA: Relief of moderate to severe pain after surgery

    Mechanism 
    Nalbuphine is primarily a κ-agonist / partial μ-antagonist analgesic. Nalbuphine exhibits a ceiling effect on respiratory depression such that increases in dose greater than 30 mg do not produce further respiratory depression. Naldebain® is a long-acting analgesic injection that contains a prodrug of nalbuphine in a special formulation designed for intramuscular (IM) administration only.

    The sustained release of Naldebain® prodrug from the IM injection site and its quick conversion to nalbuphine upon absorption into the blood stream allows nalbuphine plasma levels to be maintained at therapeutic range longer than IM administration of nalbuphine itself. Thus a single dose of Naldebain® prior to surgery would provide sufficient pain relief up to several days post-surgery, which greatly improves patient compliance and reduces healthcare costs.

    Trial Information
    A series of nonclinical studies and two Phase I clinical trials have been completed for Naldebain®. A Phase II/III clinical trial was completed in 2015 Q2. The Phase I pharmacokinetic data show that one IM injection of Naldebain® resulted in sustained plasma levels of nalbuphine over a period of seven days, underscoring the long-acting effect of the formulation.

    Furthermore, Naldebain® exhibited lower maximum blood concentration (Cmax) than nalbuphine itself, and thus has a better safety profile than nalbuphine itself.

    The results of the Phase III clinical trial in hemorrhoidectomy patients (N=209) showed pain assessment calculated as the area under the curve (AUC) of VAS pain intensity scores through 48 hours post surgery, and the consumption of oral analgesics from Day 3-7, in subjects from the Naldebain® group were lower than those in the control group showing statistical significance (p-value of 0.0052 and 0.0002, respectively).

    In terms of safety, no drug-related serious adverse event (SAE) were reported in patients administered with Naldebain®.