Principles of Antibiotic Formulary Selection for P&T Committees: OTHER COST FACTORS

Monitoring Costs

Various factors may need to be considered in relation to the acquisition and administration costs for hospitalized patients receiving IV antibiotic therapy, such as the cost of monitoring certain antibiotics. Traditionally, aminoglycosides have provided the best example of such hidden costs. For patients receiving IV gentamicin every eight hours, serial serum crea-tinine levels and periodic peak-and-trough gentamicin levels need to be monitored. The price of generic gentamicin might be less than $1 per day, but the cost of monitoring tests is often overlooked, even though this cost exceeds the acquisition cost of the drug itself. Antibiotics that warrant monitoring of platelets or periodic liver-function tests also illustrate cost factors that need to be calculated to determine the true cost of antimicrobial therapy with different agents.

Obligatory Costs of Additional Therapy

Obligatory combination therapy is another hidden cost factor to be considered in determining costs of antimicrobial usage. For example, the clinician who wishes to establish the cost of IV metronidazole (e.g., Pharmacia) therapy for use in intra-abdominal or diabetic foot infections must consider the cost of the obligatory additional drug to be used. In diabetic foot infections, metronidazole is active against the Bacteroides fragilis portion of the infection, but another antimicrobial agent with antistaphylococcal and antiaerobic gram-negative bacillary coverage must also be provided. The same is true for patients with intra-abdominal sepsis. Metronidazole should not be used alone and must always be combined with an agent with antiaerobic gram-negative bacillary activity. For these reasons, the cost of the obligatory additional drug must be factored in to arrive at the actual cost of using metronidazole canadian in this situation.

Side Effects

Side effects have been discussed in Part 4 of this series (P&T, September 2003). Antibiotics that are associated with laboratory abnormalities increase the institution’s actual cost of using the drug. Antibiotics that cause clinical side effects (e.g., Clostridium difficile diarrhea, seizures, phlebitis) should also be considered in any pharmacoeconomic analysis.


The impact of resistant organisms in the hospital has been discussed in Part 3 of this series (P&T, August 2003). Using antibiotics with a known resistance potential may necessitate the use of other more expensive drugs if serious resistance problems are encountered. Opting for drugs with a low resistance potential minimizes the economic and medical implications of antibiotics that have been associated with problems of resistance.

Therapy Failure

The cost of failed therapy is not inconsequential and is often underappreciated. It is important, from the start, to get things right. Patients’ needs are best served by initiating appropriate antimicrobial therapy as soon as possible after a working diagnosis is made, particularly in the case of patients who are critically ill. The sicker the patient, the more crucial it is to initiate the correct therapy at the outset. canadian cialis online

A stepwise approach to antimicrobial therapy should be avoided because it is costly and forfeits precious time. If an antimicrobial that is less potent than another one is prescribed for a particular indication, the potential for a delayed or ineffective therapeutic response is present. Precious time is wasted when one awaits a therapeutic response that could have been achieved more quickly with a more effective agent.

The chances of curing an infection are best in the early stages. If there is a delay in therapeutic response or if therapy is unsuccessful, the patient must still be given a more potent antibiotic to eradicate the infection. A more potent and effective antibiotic might, in fact, appear to be more costly on a per-unit basis than a less effective antibiotic, but it is more cost-effective in terms of outcome because it does not result in drug-related failure. Sometimes the most effective agent is not the least expensive one to acquire but is, in the clinical setting, the one that is cost-effective, such as piperacillin/tazobactam, the carbapenems (e.g., meropenem) (Pharmacia), and others.

Category: Drug

Tags: Antibiotic, Committees

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