Fentora is available as a dissolving oral tablet. It is designed to be placed under the tongue, above a rear molar, or between the upper cheek and gum. The tablet should not be crushed or chewed and usually fully dissolves within 25 minutes. The medication is only given to cancer patients who are used to and experienced with narcotics and if the patient is taking other narcotics daily for around-the-clock pain. Fentora has a high risk of addiction, so it is important to take the medication exactly as prescribed to reduce the risk of substance misuse. It is initially started at a dose of 100 mcg as needed and can be gradually increased by a doctor if breakthrough pain is severe. It is not recommended to take more than two tablets during one breakthrough episode. Taking more than prescribed can result in severe side effects and possibly cause an overdose.