General Information

Subsys is a sublingual spray formulation of fentanyl. Fentanyl is an opioid agonist whose principal therapeutic action is analgesia. The precise mechanism of the analgesic action is unknown although fentanyl is known to be a mu-opioid receptor agonist.

Subsys was specifically approved for the management of breakthrough pain in adult cancer patients who are already receiving and who are tolerant to around-the-clock opioid therapy for their underlying persistent cancer pain.

Susbsys is supplied as a spray for sublingual administration. Subsys should be individually titrated to a dose that provides adequate analgesia and minimizes side effects. The initial dose of Subsys to treat episodes of breakthrough cancer pain is always 100 mcg. From this initial dose, the dose should be titrated to provide adequate analgesia using a single Subsys dose per breakthrough cancer pain episode with tolerable side effects. For each breakthrough pain episode treated, if pain is not relieved after 30 minutes, patients may take ONLY ONE additional dose of the same strength for that episode. Thus the maximum of two doses of Subsys is recommended for any breakthrough pain episode. Patients MUST wait at least 4 hours before treating another episode of breakthrough pain with Subsys.

Clinical Results

FDA Approval
The FDA approval of Subsys was based on a double-blind, placebo-controlled, crossover study in opioid tolerant adults with cancer and breakthrough pain. The subjects received Subsys from 100 mcg per dose to 1600 mcg per dose. The study began with an open-label dose titration period followed by a double-blind treatment period. The goal of titration was to find the dose of Subsys that provided adequate analgesia with acceptable side effects. Once a successful dose was established, subjects were enrolled into the double-blind period and randomized to a sequence of 10 treatments; 7 with Subsys and 3 with placebo. The subjects assessed pain intensity on a 100 mm visual analog scale that rated the pain as 0=none to 100=worst possible pain. With each episode of breakthrough pain, pain intensity was assessed first and then treatment was administered. Pain intensity (0-100) was then measured at 5, 10, 15, 30, 45 and 60 minutes after the start of administration. The primary endpoint was the summed pain intensity difference from baseline to 30 minutes after dosing. Out of 130 subjects who entered the titration phase, 98 (75%) were able to titrate to a dose that adequately reduced pain with tolerable side effects and entered into the double-blind period. Subsys produced a statistically significantly greater reduction in pain intensity compared to placebo as measured by the Summed Pain Intensity Differences scale (SPID) at 30 minutes.

Side Effects

Adverse events associated with the use of Subsys may include, but are not limited to, the following:

• vomiting
• nausea
• constipation
• dyspnea
• somnolence

Mechanism of Action

Subsys is a sublingual spray formulation of fentanyl. Fentanyl is an opioid agonist whose principal therapeutic action is analgesia. The precise mechanism of the analgesic action is unknown although fentanyl is known to be a mu-opioid receptor agonist.

Additional Information

For additional information regarding Subsys or breakthrough cancer pain, please visit the Insys Therapeutics web page.