The drug may cause addiction or become habit forming. Control of access and duration of therapy by a health care professional is required. Serious adverse reactions to the drug are known to occur or have a recognized potential to occur at normal therapeutic dosage levels. Adverse experiences require special monitoring or intervention by a health care professional. There exists a narrow margin of safety between the therapeutic and toxic dosages of the drug, either in the general population, or in identified subpopulations, or in patients with multiple medical problems.
Safe use requires the involvement and intervention of a health care professional.
Serious interactions of the drug are known to occur. Use of the drug has contributed to, or is likely to contribute to, the development of resistant strains of microorganisms. The mechanism of action of the drug is known but the consequences of widespread use are not adequately established. Unexpected effects of the drug must be evaluated and reported by a health care professional. The therapeutic effects of a newly released drug are based on new or unknown mechanisms of action, but the consequences of widespread use are not adequately established.