PrinciplesCost-effective antimicrobial therapy begins at the formulary level. P&T committee members who select antibiotics for each major clinical area of usage should choose one or two agents in each antibiotic category to meet the needs of the institution. The antibiotics in each category should satisfy all of the factors that are important in selection—the spectrum of coverage, appropriate pharmacokinetic properties, a low potential for resistance, and a good safety profile—before cost analysis is undertaken.

P&T committees should view the acquisition cost in the proper clinical perspective by taking into account the true cost of the antibiotic when IV administration charges are factored in. All other things being equal, the committee should opt for drugs with less frequent dosing intervals to minimize the impact of the cost of the IV route.
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Intravenous-to-Oral Switch Therapy

Antibiotics that have an oral equivalent should have a decided advantage at the formulary level. With intravenously administered antibiotics, the single most important cost factor, after acquisition costs, is the frequency of administration. The single most important cost-saving strategy for institutions is an extensive IV-to-PO switch program. Because the cost of oral agents is generally much lower than that of their IV counterparts, every effort must be made to switch to equivalent oral therapy as soon as is clinically possible.

No other single change has the pharmacoeconomic implications of IV-to-PO switch therapy. Switching to oral antibiotic therapy means not only lower antibiotic costs but also fewer side effects and an earlier hospital discharge, thereby decreasing the patient’s length of stay—an important consideration in institutional reimbursement systems. The main attributes of oral antibiotic therapy, after cost considerations are taken into account, are the drug’s dosing frequency and safety profile, both of which affect patient compliance. The more inexpensive the oral agent, the more acceptable the inconvenience of frequent dosing and the additional side effects might be.

Choosing the Preferred Antibiotic

At the hospital formulary level, rarely is the choice between a “good” agent and a “poor” one; rather, the choice is between good agents with minor differences in cost and side-effect profiles or resistance potentials. These represent the most difficult decisions that hospital formulary committees must make; in another sense, though, they are the least important problems faced by P&T committees, because either choice would be cost-effective and acceptable to most members of the hospital medical staff. Because expenses are an overriding priority in today’s managed health care systems, cost considerations may persuade a formulary committee to accept a tolerable level of infrequent side effects to conserve financial resources. Only in rare circumstances should cost be the sole consideration in decision-making, however.


The hospital P&T committee’s task is best summarized as follows: to select IV antibiotics (preferably with longer dosing intervals, a low resistance potential, and a good safety profile) that have oral equivalents for an IV-to-PO switch program. Working in concert with the pharmacy department and infectious disease clinicians, P&T committees should implement a comprehensive IV-to-PO switch program in the institution.

The most cost-effective approach would be not to use not the least expensive agent but to use the one that is the most potent and free of side effects and resistance, with conversion to an oral equivalent as soon as possible in the clinical setting. It is essential to choose the best, but not necessarily the least expensive, agents for the initial critical phase of infection. Switching to an oral agent as early as possible is the most efficient use of hospital resources and therefore benefits both the patient and the institution.