There have been reports of deaths attributable to the use of fentanyl buccal tablets (Fentora). The tablets are used to treat breakthrough pain in patients who've been receiving an opioid analgesic for cancer pain and have developed a tolerance to opioids. Administration of the drug to treat acute or postoperative pain, headache, migraine, or sports injuries can result in life-threatening respiratory depression. Opioid tolerance is considered present if the patient has taken one of the following for at least one week: 60 mg or more of oral morphine daily; 25 micrograms or more of transdermal fentanyl per hour; 30 mg or more of oral oxycodone daily; or 8 mg or more of oral hydromorphone or an equianalgesic amount of another opioid daily.

Another cause of fentanyl buccal tablet overdoses is a change to the tablets from another fentanyl product. The tablets have a greater bioavailability than do other oral fentanyl preparations, so in changing from the use of other such products (oral transmucosal fentanyl citrate, [Actiq], for example) the dose should be lowered-administration of the same dose can result in an overdose and possibly fatal respiratory depression (see the Dosage and Administration section of the product labeling to make the appropriate adjustment).

An overdose can also result from taking too many tablets-if pain is not relieved within 30 minutes after one tablet is taken, only a second one of equal dose may be taken-no additional tablets should be taken either for that episode of breakthrough pain or for at least the next four hours, even if there are subsequent episodes.