Antimicrobial drug interactions

As mentioned previously, some infectious diseases pharmacists have established effective clinical practices in the outpatient setting. The most common example of this is the presence of a pharmacist in an HIV clinic. The myriad of antimicrobial drug interactions and adverse effects associated with antiretroviral therapy, the need to periodically assess antiretroviral efficacy, and the considerable potential for noncompliance literally necessitate the need for a pharmacist in any established HIV clinic. Infectious diseases pharmacists work with infectious diseases and/or immunology physicians. Pharmacists conduct medication histories and answer drug information questions. In some settings, they may act under protocol to assess patient response to antiretroviral therapy based on virologic and immunologic measures, and to make appropriate modifications in therapy. 

Drug-specific considerations in antimicrobial selection include the spectrum of activity, effects on nontargeted microbial flora, appropriate dose, pharmacokinetic and pharmacodynamic properties, adverse-effect and drug-interaction profile, and cost. 

Provide patient education with regard to appropriate use of antimicrobials (e.g., dose, interval), adverse effects, and drug interactions (which may play a role in therapy failure and increased toxicity). 

Every patient receiving antimicrobial therapy for skin and soft tissue infections must be monitored for efficacy and safety. Efficacy typically is manifested by reductions in temperature, white blood cell count, erythema, edema, and pain that begin within 48 to 72 hours. To ensure safety, dose antibiotics according to renal and hepatic function as appropriate, and monitor for and minimize adverse drug reactions, allergic reactions, and drug interactions. 

Antimicrobial Adverse Events Drug-Drug Interactions... 

Gillum JG, Israel DS, Polk RE Pharmacokinetic drug interactions with antimicrobial agents. Clin Pharmacokinet 1993,25 450-482. 

Concomitant disease states. A list of selected drug interactions involving antimicrobials is provided in Table 35-3. 

The use of antimicrobials has been controversial, although antibiotics are an important component of treatment. Agents should be selected that are effective against likely pathogens, have the lowest risk of drug interactions, and can be administered in a manner that promotes compliance (see Table 43-1). 

I.a.3. Interaction between Antimicrobial Drugs and Micro-organisms... 

Synergy studies are in vitro tests that attempt to measure synergistic, additive, indifferent, or antagonistic drug interactions. In general, these tests have not been standardized and have not correlated well with clinical outcome. (See section on Antimicrobial Drug Combinations for details.)... 

TABLE 35-3 Major Drug Interactions with Antimicrobials 1... 

The quinolone antimicrobial drugs gemifloxacin, levo-floxacin, and sparfloxacin do not interact with digoxin. 

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