Drugs Limitations

Caution New Drug-Limited by Federal (or United States) law to investigational use . 

Over-the-counter drugs prescription drugs limited to doctor s orders... 

Adverse reactions to the administration of adenosine are fairly common however, the short half-life of the drug limits the duration of such events. The most common adverse effects are flushing, chest pain, and dyspnea. Adenosine may induce profound bronchospasm in patients with known reactive airway disease. The mechanism for bronchospasm is unclear, and the effect may last for up to 30 minutes despite the short half-life of the drug. 

These drugs limit the amount of tetrahydrofolate available for use in purine synthesis and, thus, slow down DNA replication in mammalian cells. These compounds are, therefore, useful in treating rapidly growing cancers, but are also toxic to all dividing cells. 

To provide a context for our discussion of Rx-to-OTC switches, we will describe briefly the classifications of drugs that must be limited to prescription use. Specifically, the following types of drugs must be sold for prescription use only (1) drugs not safe for use except under the supervision of a licensed practitioner because of toxicity or other potential for harmful effect, method of use, or the collateral measures necessary for use and (2) drugs limited to prescription under an approved NDA [87]. FDA may remove by regulation a drug subject to the premarket approval requirements from prescription status when such requirements are not necessary for the public health [88]. 

Labeling A mock-up or printed representation of the proposed labeling that will be provided to investigators in the proposed clinical trial should be submitted. Investigational labels must carry a caution statement as stated earlier. The required statement reads Caution New Drug—Limited by Federal (or United States) law to investigational use. ... 

Erythromycin 500 mg p.o. q.i.d. Second line drug limited experience... 

Newer antipsychotic agents may also be helpful with regard to these concerns. The atypical antipsychotic clozapine was the first of the atypical antipsychotics, which offer significant advantages over typical antipsychotics (Kane et al. 1988). Clozapine is effective in many patients unresponsive to treatment with typical antipsychotics. It also seems to be associated with few extrapyra-midal symptoms (EPS) and a lower risk for TD. However, other features of the drug limit its use by African Americans. 

Prevent brain penetration of drugs Limit oral absorption... 

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