Coinfection with HIV and HCV: more questions than answers?

Chronic infection with the hepatitis C virus (HCV) is a major public health threat in the United States and worldwide. By sharing some routes of transmission, persons infected with the human immunodeficiency virus (HIV) are at risk for coinfection with HCV As a result, hepatic cirrhosis, end-stage liver disease, and hepatocellular carcinoma due to chronic infection with HCV are important causes of both morbidity and mortality in coinfected patients. The advent of highly active antiretroviral therapy improved the management of patients with HIV, leading to decreased morbidity and better survival. As patients infected with HIV live longer, their risk of long-term sequelae from chronic HCV increases. Coinfection with HIV may be associated with rapid progression of chronic HCV. In contrast, the effect of HCV on the natural history of HIV is less clear. Data regarding treatment of HCV in HIV-coinfected patients are limited.

Pharmacodynamics of fluconazole, itraconazole, and amphotericin B against Candida albicans.

The objective of this study was to evaluate the pharmacodynamic activity of fluconazole, itraconazole, and amphotericin B against Candida albicans. Susceptibilities were determined according to the NCCLS guidelines (M27). Time-kill studies were performed using antifungal concentrations of 0.25-32 x MIC. Samples were withdrawn at predetermined timepoints, then plated using a spiral plater. Colony counts were determined after incubation at 35 degrees C for 24 h. The AUKC(0-48) was plotted against the concentration/MIC ratio. Candida isolates (95-2672, 96-15, and 95-2542) were classified as susceptible, susceptible-dose dependent, and resistant to fluconazole and itraconazole (MIC = 0.25 and 0.03 microg/mL, 32 and 0.5 microg/mL, 64 and 1 microg/mL; respectively). All three isolates were susceptible to amphotericin B (MIC = 0.13 microg/mL). Fluconazole inhibited the growth of the susceptible and S-DD isolates and was ineffective at all concentrations against the resistant isolate. Itraconazole, on the other hand, inhibited growth of the susceptible isolate, but was ineffective for the S-DD and resistant isolates. Maximal effectiveness was noted at the concentration 8 x MIC and 2 x MIC for fluconazole and itraconazole, respectively. Amphotericin B demonstrated concentration-dependent antifungal activity. The times necessary for the colony counts to fall below the limit of quantification were inversely related to increasing concentrations of amphotericin B. The maximal effect for amphotericin B was recorded at 2 x MIC. In summary, the triazoles inhibit growth of susceptible C. albicans; however, careful consideration should be given to the MIC for S-DD isolates because itraconazole may not be active if the MIC is reported in the higher susceptible-dose dependency range. In reference to amphotericin B, optimal activity may be achieved by maximizing the peak drug concentration/MIC ratio.

Pharmacokinetics and pharmacodynamics of aztreonam administered by continuous intravenous infusion.

The pharmacodynamic parameter that appears to correlate best with a successful therapeutic outcome with beta-lactam antibiotics is the length of time the serum antibiotic concentration remains above the minimum inhibitory concentration (MIC) for the infecting pathogen. By maximizing this parameter, continuous administration of beta-lactam and related antibiotics by intravenous infusion could represent the optimal mode of drug administration. The pharmacokinetic and pharmacodynamic properties of ceftazidime administered by continuous intravenous infusion have been evaluated previously. Aztreonam is a monobactam antibiotic with similar pharmacokinetic and microbiologic activity to that of ceftazidime. This study evaluated the pharmacokinetic and pharmacodynamic characteristics of aztreonam administered as a continuous intravenous infusion in healthy volunteers against multiple clinical isolates. Five men and 3 women received 6 g of aztreonam administered by continuous intravenous infusion over 24 hours. Blood samples were collected before the infusion and at 0.5, 1 through 8, 12, 18, and 24 hours after the start of the infusion. Pharmacokinetic parameters were determined by standard equations. In vitro susceptibility testing was performed using National Committee for Clinical Laboratory Standards guidelines for 4 clinical isolates of gram-negative bacteria (2 each of Escherichia coli and Pseudomonas aeruginosa). Serum inhibitory titers (SITs) were determined in duplicate for each clinical isolate at 0 and 24 hours. The subjects' mean (+/- SD) age was 29.3+/-4.4 years; mean weight, 74.6+/-14.0 kg; and calculated mean creatinine clearance, 107+/-13 mL/min. For the pharmacokinetic parameters, mean (+/- SD) values were as follows: steady-state serum concentration, 40.9+/-8.8 microg/L; half-life, 1.5+/-0.4 hours; elimination rate constant, 0.50+/-0.13 hours(-1); steady-state volume of distribution, 0.18+/-0.04 L/kg; and total body clearance, 6.1+/-1.2 L/h. The MICs were 0.0625 and 0.125 microg/mL against the 2 E coli isolates and 4 microg/mL against both P aeruginosa isolates. The median SITs against the E. coli isolates were 1:256 and 1:512, and against the P. aeruginosa isolates were 1:8 and 1:16. At steady state, II subjects had serum concentrations of aztreonam > or =4 times the MIC for each organism. These findings suggest that further clinical study of the administration of aztreonam by continuous intravenous infusion is warranted.

Therapeutic drug monitoring of systemic antifungal therapy.

The use of systemic antifungal therapy has significantly increased in recent years. Individualization of antifungal therapy through the use of serum or plasma concentrations has been suggested, although no specific recommendations have been developed. The important criteria for therapeutic drug monitoring and which of these criteria are satisfied by systemic antifungal agents are presented in this review. No one antifungal is ideally suited for application of therapeutic drug monitoring, but, under certain circumstances, obtaining serum or plasma concentrations can be justified. In patients who are susceptible to flucytosine toxicity, serum flucytosine concentrations should be monitored in an effort to avoid untoward side-effects. In contrast, therapeutic drug monitoring of amphotericin B is not recommended in the clinical setting. Demonstrating that ketoconazole and itraconazole are reaching the systemic circulation by obtaining serum concentrations may be clinically useful due to the large variability in their absorption and issues of patient compliance which may be seen with these agents. The bioavailability of fluconazole is much less varied although validation of compliance is a situation where obtaining serum concentrations may provide additional information.

Influence of antibiotic and E5 monoclonal immunoglobulin M interactions on endotoxin release from Escherichia coli and Pseudomonas aeruginosa.

Recent controversy surrounding the activity of monoclonal antibodies against endotoxin highlights the necessity of identifying all factors associated with increased mortality, one of which is endotoxin concentrations. Antibiotics may induce different patterns of endotoxin release. We compared the release of free endotoxin (in endotoxin units per milliliter) over 6 h and changes in numbers of CFU of exponentially growing Escherichia coli and Pseudomonas aeruginosa (10(6) to 10(7) CFU/ml) cultured in chemically defined endotoxin-free broth combined with pooled human serum and/or 10 micrograms of E5 immunoglobulin M monoclonal antibody per ml. MICs and MBCs were tested in each medium at the same inoculum. The inoculum was exposed to antibiotics at a single fixed multiple of the MIC for each medium (range, two to eight times the MIC). E5 antibody had no effect on MICs, MBCs, bactericidal activity, or endotoxin release. In the presence of 50% serum, amikacin, ceftazidime, imipenem, and ofloxacin each killed equivalent amounts of E. coli over 6 h; however, ceftazidime induced the highest release of endotoxin. Amikacin and ofloxacin produced the most favorable ratio of endotoxin release to amount of bacterial killing. In the presence of 50% serum, ceftazidime and imipenem reduced the P. aeruginosa inoculum to the greatest extent over 6 h. Although its bactericidal activity was diminished, ofloxacin caused the lowest release of free endotoxin. Imipenem and ofloxacin showed similar low ratios of endotoxin release to bacterial killing. In summary, antibiotic class, presence of serum, and type of organism influenced bactericidal activity and endotoxin release.