Episode 115: Oral vancomycin prophylaxis for C. Diff, fentanyl fluconazole interaction, and a free drug information resource

In this episode I’ll:

1. Discuss an article about using oral vancomycin to prevent recurrent Clostridium difficile infection.

2. Answer the drug information question “Is the interaction between fentanyl and fluconazole significant for critical care patients?”

3. Share a resource for free drug information.

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Article

Efficacy of Oral Vancomycin in Preventing Recurrent Clostridium difficile Infection in Patients Treated With Systemic Antimicrobial Agents

Lead author: Nicholas W. Van Hise

Published in Clinical Infectious Diseases August 2016

Background

In high-risk patients, oral vancomycin prophylaxis against Clostridium difficile infection has been used when systemic antimicrobial therapy needs to be continued.

The authors sought to evaluate whether oral vancomycin prophylaxis was effective in preventing Clostridium difficile infection.

Methods

The trial was a retrospective cohort study in a large community teaching hospital. 203 patients were eligible for inclusion in the study.

Results

71 patients received oral vancomycin prophylaxis at a dose of 125 mg po bid, and 42 patients received oral vancomycin prophylaxis at a dose of 250 mg po bid. The control group consisted of 132 patients who did not receive oral vancomycin prophylaxis. Characteristics were similar between groups. The oral vancomycin prophylaxis group may have been at greater risk for Clostridium difficile infection as they were more likely to receive a carbapenem or a gastric acid suppressing agent.

Clostridium difficile infection was diagnosed in only three (4.2%) patients in the oral vancomycin prophylaxis group compared with 26.6% in the control group. On closer analysis two of the three patients in the oral vancomycin prophylaxis group were not felt to have symptomatic Clostridium difficile infection.

Conclusion

The authors concluded:

Oral vancomycin prophylaxis (OVP) may be effective in reducing the risk of recurrent CDI in patients who require systemic antimicrobial therapy. Prospective studies are needed to better define the risks and benefits of OVP in this vulnerable patient population.

Discussion

Often antibiotic use cannot be avoided in hospitalized patients. It is comforting to have this information that suggests oral vancomycin prophylaxis can be used to significantly mitigate the risk of recurrent Clostridium difficile infection in such high-risk patients. I would not be surprised to see a similar study done with fidaxomicin.

Drug information question

Q: Is the interaction between fentanyl and fluconazole significant for critical care patients?

A: No.

This is yet another interaction that my favorite book – Hansten and Horn’s Top 100 Drug Interactions demystifies. Computer alerts flash like crazy over the fentanyl – fluconazole interaction with category 1 or 2 alerts.

But fluconazole is a weak CYP3A4 inhibitor except in larger doses. Fentanyl also has another pathway of elimination, p-glyco protein, which is unaffected by fluconazole. Finally, fentanyl doses are titrated, and patients are closely monitored in critical care settings; even if there were an interaction, it would not likely be clinically significant.

Hansten & Horn assign this interaction their lowest category: “Class 3: Assess risk and take action if necessary”. I was explaining this book to an anesthesiologist friend of mine and he summed it up by saying “Hansten & Horn have the guts to assign a realistic interaction risk to drug combinations.” That is exactly why I like this book so much.

Resource

PharmGuide is a collection of free drug information resources. This guide is intended to highlight the best free drug information resources on the web. It is maintained by members of the Pharmacy and Drug Information Section of the Medical Library Association, members of the Special Libraries Association, and individual members of the American Association of Colleges of Pharmacy. There are resources for pricing, toxicology, pronunciation, and much more.

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