In vivo efficacy of zidovudine (3''-azido-3''-deoxythymidine) in experimental gram-negative-bacterial infections.

The therapeutic efficacy of orally administered zidovuldine (3'-azido-3'-deoxythymidine) was determined in animals infected with Escherichia coli and Salmonella dublin. The 50% effective dose (ED50) of zidovudine (9.6 to 11.8 mg/kg of body weight) compared favorably with that of trimethoprim (19.4 to 22.2 mg/kg) in mice with systemic E. coli infection. At 50 mg/kg, both zidovudine and ampicillin reduced the number of bacteria in the kidneys of mice and prevented lethal infection in mice with ascending pyelonephritis caused by E. coli. Zidovudine prevented a lethal S. dublin infection in calves over a wide dose range (8.0 to 31.0 mg/kg per day). Zidovudine levels in plasma of uninfected mice were 28.2 +/- 4.5 and 7.9 +/- 2.2 micrograms/ml at 30 and 60 min, respectively, exceeding the MICs for the bacteria used in the infections. Few zidovudine-resistant strains were observed. The in vivo data raise the possibility that zidovudine may have an antibacterial effect in patients receiving this therapy.     

A randomized controlled trial of a protease inhibitor (saquinavir) in combination with zidovudine in previously untreated patients with advanced HIV infection

This study assessed the activity and tolerability of an HIV-protease inhibitor, saquinavir, alone or in combination with zidovudine. A total of 92 previously untreated HIV-infected patients with CD4 cell counts < 300 cells/mm3 participated in a parallel, randomized double-blind study. Patients were randomized to receive one of five treatments, each three times a day: 600 mg of saquinavir; 200 mg of zidovudine; 75, 200 or 600 mg of saquinavir in combination with 200 mg of zidovudine. The primary treatment period was 16 weeks, with monthly extensions in patients who did not show major disease progression or toxicity. The main measures of the efficacy of therapy used were changes in CD4 cell counts and in the concentration of HIV-1 RNA in the plasma (as determined by quantitative polymerase chain reaction). The 600 mg dose of saquinavir in combination with zidovudine induced a 1.6 log (after 4 weeks) and a 0.7 log (after 16 weeks) median reduction in plasma RNA concentration; this reduction was greater than those seen in the other four treatment groups. The combination of 600 mg of saquinavir with zidovudine also resulted in a larger and more sustained improvement in the CD4 cell count than either saquinavir or zidovudine monotherapy or the other combination therapies. In the group receiving 200 mg of saquinavir in combination with zidovudine, the maximal median change in CD4 cell count occurred at week 2 (85 cells/mm3), and by week 16 had fallen to 15 cells/mm3. In the group receiving 600 mg of saquinavir plus zidovudine, the median change in CD4 cell count remained high for the 16-week period (median change of 48 cells/mm3 at week 2 and 61 cells/mm3 at week 16). Saquinavir was safe and very well tolerated, either alone or in combination with zidovudine. The incidence of adverse events was greater in the four groups receiving zidovudine therapy, and all the most commonly reported adverse events have previously been associated with zidovudine therapy. Few changes in laboratory values occurred during the study, except for known zidovudine-associated toxicities. The most frequent abnormalities were raised aspartate aminotransferase and alanine aminotransferase levels, depressed calcium levels, and abnormally high or low phosphate levels. Despite the low oral bioavailability of saquinavir, combined virological and immunological data show definite antiviral activity in vivo for the combination of saquinavir at 600 mg plus zidovudine at 200 mg (each three times daily). The combination of drugs with different mechanisms of action represents an advance in the treatment of HIV infection.     

Comparison of a new triazole, posaconazole, with itraconazole and amphotericin B for treatment of histoplasmosis following pulmonary challenge in immunocompromised mice

A murine model of intratracheally induced histoplasmosis in immunocompromised B6C3F(1) mice was used to evaluate a new triazole antifungal agent, posaconazole. This compound was previously shown to be comparable to amphotericin B and superior to itraconazole for the treatment of histoplasmosis in immunocompetent mice. The current study used mice that were depleted of T lymphocytes by intraperitoneal injection of anti-CD4 and anti-CD8 monoclonal antibodies beginning 2 days before infection and continuing at 5-day intervals until completion of the study. Groups of B6C3F(1) mice that were depleted of CD4 and CD8 T cells were infected with an inoculum of 10(4) Histoplasma capsulatum yeasts. All mice receiving posaconazole at 1 or 0.1 mg/kg of body weight/day, amphotericin B at 2 mg/kg every other day (qod), or itraconazole at 75 mg/kg/day survived to day 29. Only 60% of mice receiving itraconazole at 10 mg/kg/day and none receiving amphotericin B at 0.2 mg/kg qod survived to that date. Fungal burdens were determined at day 14 of infection, 1 day after discontinuation of therapy. Quantitative colony counts and Histoplasma antigen levels in lung and spleen tissues declined following treatment with amphotericin B at 2 mg/kg qod, posaconazole at 5 and 1 mg/kg/day, and itraconazole at 75 mg/kg/day but not in mice treated with amphotericin B at 0.2 mg/kg qod or itraconazole at 10 mg/kg/day. Posaconazole at 0.1 mg/kg/day reduced fungal colony counts and antigen levels in spleens but not in lungs. This study shows posaconazole activity for the treatment of histoplasmosis in immunosuppressed animals.     

Pharmacokinetic evaluations of low- and high-dose zidovudine plus high-dose acyclovir in patients with symptomatic human immunodeficiency virus infection.

The pharmacokinetics of zidovudine were evaluated in 41 patients with Centers for Disease Control HIV class IVA infection. The patients were assigned escalating doses of zidovudine (300, 600, or 1,500 mg daily) and were randomized to receive either zidovudine alone or zidovudine with a high dose of acyclovir (4,800 mg per day). Single and multiple intravenous- and oral-dose pharmacokinetic studies were performed on days 1 and 7 and weeks 6 and 12 of therapy. Zidovudine concentrations were analyzed by high-pressure liquid chromatography. Pharmacokinetic parameters were estimated by noncompartmental methods. Zidovudine concentrations in serum declined in a biphasic manner, with half-lives ranging from 1 to 2 h, and were independent of acyclovir administration or length of zidovudine therapy. The median time of peak concentrations in serum following oral doses was 0.75 h (range, 0.25 to 3 h). Accumulation of zidovudine in serum was not observed, but the maximum concentration of drug in serum (Cmax) and the area under the concentration-time curve increased proportionally with increased zidovudine doses. Mean day 7 oral Cmax values were 0.20 +/- 0.12, 0.55 +/- 0.33, and 1.0 +/- 0.5 micrograms/ml for 17 patients receiving total daily doses of, respectively, 300, 600, and 1,500 mg of zidovudine alone, whereas Cmax values were, respectively, 0.27 +/- 0.18, 0.43 +/- 0.33, and 1.2 +/- 0.80 micrograms/ml for 15 comparably treated recipients of zidovudine plus acyclovir (P was not significant). The median bioavailability of oral zidovudine was 67% (42 to 120%) and did not vary with dosage. Absolute and apparent total body clearances were similar among the patients given the various zidovudine doses regardless of whether there was concomitant acyclovir therapy. Drug-related toxicities were observed more frequently in the subjects who received high doses of zidovudine than they were in those who received median and low doses of zidovudine (P=0.03). Overall, acyclovir did not influence the disposition of zidovudine over a wide range of zidovudine doses. No unusual toxicities could be attributed to the zidovudine and high-dose acyclovir combination during the 12-week observation period.     

Pharmacokinetics of SCH-39304 in human immunodeficiency virus-infected patients following chronic oral dosing.

The pharmacokinetics of SCH-39304, an investigational, orally active, broad-spectrum antifungal agent, were evaluated in 17 adult, human immunodeficiency virus-positive males. Patients were studied on days 1 and 16 and were divided into the following three treatment groups: (i) patients with culture-proven oropharyngeal candidiasis who were not receiving concurrent zidovudine therapy and who were treated with 50 mg of SCH-39304 daily (n = 6); (ii) patients with culture-proven oropharyngeal candidiasis who were receiving concurrent zidovudine therapy and who were treated with 50 mg of SCH-39304 daily (n = 5); and (iii) patients with or without oropharyngeal candidiasis who were receiving concurrent zidovudine therapy and who were treated with 200 mg of SCH-39304 daily (n = 6). All patients received a single daily dose of the study medication for 16 days. Plasma samples for SCH-39304 concentration measurement were collected for 6 h following the initial dose and for 504 h following the day 16 dose. Urine was collected for 24 h following SCH-39304 administration on days 1 and 16. All samples were assayed for SCH-39304 by gas chromatography. Wide intersubject variations in SCH-39304 plasma concentration-versus-time profiles were observed on each study day. Absorption appeared to be slow, with mean day 1 peak plasma SCH-39304 concentrations of 1.2 micrograms/ml at 2.1 h (50 mg) and 3.9 micrograms/ml at 4.0 h (200 mg) after drug administration. Mean peak plasma SCH-39304 concentrations on day 16 were 7.6 micrograms/ml at 4.3 h (50 mg) and 17.2 micrograms/ml at 3.2 h (200 mg) after drug administration. Mean elimination half-lives on day 16 for the 50- and 200-mg daily dosages were 100 and 89 h, respectively. SCH-39304 was cleared primarily unchanged in the urine. Mean areas under the plasma concentration-versus-time curve (from 0 to 24 h) on day 16 reflect a lower than expected increase with the 200-mg/day regimen (314.5 microgram.h/ml) compared with that for the 50-mg/day regimen (139.9 microgram.h/ml), suggesting the potential for reduced bioavailability at higher dosages. No significant effect of concurrent zidovudine therapy on the kinetics of SCH-39304 was observed.     

Early versus deferred zidovudine monotherapy: impact on AIDS-free time and survival in the multicenter AIDS cohort study

The objective of this study was to compare the time to AIDS and to death between men receiving zidovudine therapy before or not before the diagnosis of AIDS. For the time to AIDS comparison, 821 men receiving zidovudine therapy before the diagnosis of AIDS were pair matched with men who did not receive zidovudine therapy until after diagnosis on their CD4 cell count (+/- 75 cells/mm3), haemoglobin level (+/- 0.75 g/dl), number of clinical symptoms and study visit at the time of initiation of zidovudine therapy and were monitored for a median of 2.08 years. For the time to death comparison, 186 men who received zidovudine therapy prior to AIDS diagnosis were pair matched on the same variables to men who received zidovudine therapy only after the AIDS diagnosis, and were monitored for a median of 2.88 years. Only men with < 350 CD4 cells/mm3 who received zidovudine therapy prior to AIDS diagnosis remained AIDS free significantly longer than their pair match who did not (P < 0.0001). The median extension of time to AIDS was 0.61 years for men with < 200 CD4 cells/mm3 and 1.13 years for men with 200-349 CD4 cells/mm3. Cox regression analysis showed a significantly increased time to AIDS for the men with < 350 CD4 cells/mm3, both before and after adjustment for the use of prophylactic drugs against Pneumocystis carinii pneumonia. No difference was seen in the time to death between men receiving zidovudine therapy before or only after AIDS diagnosis. Zidovudine treatment of asymptomatic HIV-1-infected men provides significant benefit to men with < 350 CD4 cells/mm3 by extending AIDS-free time, but does not extend survival. The analytical technique used is applicable to other observational studies of treatment.     

Comparative in vitro activity of five cathelicidin-derived synthetic peptides against Leptospira,Borrelia and Treponema pallidum

OBJECTIVE: The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of five different cathelicidin-derived synthetic peptides (SMAP-29, LL-37, PG-1, CRAMP and BMAP-28) for Leptospira interrogans, Borrelia spp. and Treponema pallidum subsp. pallidum were investigated in vitro. METHODS: The MIC of individual peptides was defined as the lowest concentration able to inhibit the motility of spirochaetes after 2 h of incubation, as detected by dark-field microscopy. The MBC of individual peptides was defined as the lowest concentration at which no spirochaetes were subcultured either in cathelicidin-free medium (leptospires and borreliae) or in hamsters (T. pallidum). RESULTS: The MIC values of peptides for leptospires were highly variable, depending on the compound and the strain used. Of the five cathelicidin-derived peptides, SMAP-29 from sheep and BMAP-28 from cattle were the most active against L. interrogans serovars, with MIC values varying between 3 and 51 mg/L, depending on the strains. The MICs of the remaining synthetic peptides ranged between 4.3 and 224 mg/L. The MIC values of synthetic peptides for T. pallidum ranged between 32.3 mg/L for PG-1 and 449.4 mg/L for LL-37. The MICs of all cathelicidin-derived peptides tested for Borrelia strains ranged between 307 and 449.4 mg/L. The activity of the peptides on the motility of spirochaetes was both dose- and time-dependent. The MBC values of the peptides were the same as the MIC values. CONCLUSION: The results of this study demonstrate that the activity of cathelicidin-derived peptides against spirochaetes is fast and highly variable, depending on the species and the strain.     

The impact of zidovudine compared with didanosine on health status and functioning in persons with advanced HIV infection and a varying duration of prior zidovudine therapy. AIDS Clinical Trials Group 116/117 Study Group

The objective of this study was to compare the effects of zidovudine and didanosine on health-related quality of life in persons with advanced HIV infection and varying duration of prior zidovudine exposure. It was designed as a substudy nested in two similar placebo-controlled active-control-arm randomized trials, using sites of the AIDS Clinical Trials Group participating in the randomized trials of zidovudine versus didanosine (ACTG 116 and 117). The patients comprised 356 participants enrolled in ACTG 116 and 117. All had HIV infection and either a CD4 count of <200 cells/mm3, or a CD4 count of <300 cells/mm3 plus symptoms of HIV disease. Participants were randomized equally within strata defined by duration of prior zidovudine therapy, to receive didanosine sachets at a dose of 500 mg daily (334 mg in subjects weighing <60 kg) or 750 mg daily (500 mg in subjects weighting <60 kg) plus inactive capsules resembling zidovudine, or to receive zidovudine capsules at a dose of 600 mg daily plus inactive sachets resembling didanosine. The main outcome measures were self-reported health-related quality of life, healthcare utilization, disability, work and symptom impact. The results showed no differences in reported symptom impact or healthcare utilization, and most measures of disability were similar. In the group with more than 8 weeks of prior zidovudine therapy, several of the health status scale scores for ongoing participants were significantly better for didanosine recipients, but average differences were small. Use of several different approaches to combining health status and survival showed no differences in the overall quality-time experiences between the treatment groups. Individuals taking zidovudine, low-dose didanosine and high-dose didanosine experienced 33, 34 and 35 weeks, respectively, in at least the typical health state if they had fewer than 8 weeks of previous zidovudine therapy, and had 23, 23 and 26 weeks, respectively, if they had more than 8 weeks previous use of zidovudine. Results did not differ when data were analysed within strata ofpatients who had any versus no prior exposure to zidovudine, or AIDS versus non-AIDS status. In conclusion, functional status and health-related quality of life were substantially similar among persons receiving either zidovudine or didanosine, regardless of the duration of prior zidovudine treatment.     

Effect of dipyridamole on zidovudine pharmacokinetics and short-term tolerance in asymptomatic human immunodeficiency virus-infected subjects.

Zidovudine delays the progression of infection and prolongs the survival of human immunodeficiency virus (HIV)-infected patients, but these benefits are limited by dose-related toxicity and the cost of the drug. Dipyridamole, in micromolar concentrations, acts synergistically with zidovudine, reducing the anti-HIV 95% inhibitory concentration of zidovudine 5- to 10-fold in vitro. We sought to establish a well-tolerated dose of dipyridamole for use in combination with zidovudine and to detect clinically significant pharmacokinetic interactions. Both objectives are essential for planning studies of the efficacy of the zidovudine-dipyridamole combination. Eleven asymptomatic HIV-infected subjects (median CD4+ cell count, 311 cells per mm3), 10 of whom had been on zidovudine at 500 mg/day for at least 6 months, were admitted to the study. Zidovudine pharmacokinetics were measured on day 1. Dipyridamole was then begun at 600 mg/day (subjects 1 to 3) or 450 mg/day (subjects 4 to 11), and zidovudine and dipyridamole pharmacokinetics were measured on day 5. All subjects given 600 mg of dipyridamole per day developed headache or nausea, or both. Six of eight subjects given dipyridamole at 450 mg/day developed headache or mild nausea that resolved after a median of 2 days. The area under the zidovudine concentration-time curve was not significantly different on day 1 in comparison with that on day 5 (P = 0.11). Symptoms were significantly correlated with the maximum zidovudine concentrations, which were achieved when dipyridamole was dosed concomitantly (p = 0.03). Total (free and protein-bound) dipyridamole trough concentrations were near those demonstrating synergy with zidovudine against HIV in vitro. Dipyridamole was highly protein bound, with a median free/total dipyridamole ratio of 0.7%; the percent free/total dipyridamole ratio was inversely correlated with alpha 1 acid glycoprotein concentrations (r2 =0.66). Results of the study indicate that adjustment of the zidovudine dose was not required to achieve equivalent zidovudine concentrations when zidovudine was administered in combination with dipyridamole at the doses studied. In the short study described here, the zidovudine-dipyridamole combinations was well tolerated in asymptomatic HIV-infected subjects after the occurrence of mild transient symptoms.     

Exploratory study comparing the metabolic toxicities of a lopinavir/ritonavir plus saquinavir dual protease inhibitor regimen versus a lopinavir/ritonavir plus zidovudine/lamivudine nucleoside regimen

OBJECTIVES: To assess the safety, efficacy and metabolic toxicity of lopinavir/ritonavir + saquinavir or zidovudine/lamivudine and evaluate the pharmacokinetics of lopinavir/ritonavir + saquinavir. METHODS: HIV-1-infected, antiretroviral-naive subjects were randomized to lopinavir/ritonavir (400/100 mg) twice daily + saquinavir (800 mg) or zidovudine/lamivudine (150/300 mg) in a Phase II, 48 week study. Subjects receiving lopinavir/ritonavir + zidovudine/lamivudine initiated escalating doses of saquinavir (400, 600 and 800 mg) weekly for 3 weeks. RESULTS: By intent-to-treat (non-completer = failure) analysis, 10/16 (63%) lopinavir/ritonavir + saquinavir-treated and 7/14 (50%) lopinavir/ritonavir + zidovudine/lamivudine-treated subjects achieved plasma HIV-1 RNA <50 copies/mL (P=0.713) at week 48. Safety, tolerability, metabolic changes and truncal fat increases were similar between groups. Small decreases in the lower extremity fat in the zidovudine/lamivudine group (-6%) and a statistically significant increase in the lower extremity fat in the saquinavir group (+19%) were observed. Lopinavir/ritonavir co-administered with saquinavir 600 or 800 mg twice daily produced saquinavir concentrations similar to those previously reported for saquinavir/ritonavir 1000/100 mg twice daily. CONCLUSIONS: Treatment regimens had similar efficacy and tolerability. Metabolic parameters suggested lipoatrophy in the zidovudine/lamivudine treatment group. Saquinavir 600 and 800 mg twice daily produced concentrations similar to those previously reported for saquinavir/ritonavir 1000/100 mg twice daily.     

Clarithromycin lowers plasma zidovudine levels in persons with human immunodeficiency virus infection.

The use of antiretroviral agents and drugs for the treatment and prophylaxis of opportunistic infections has lengthened the survival of persons with AIDS. In the era of multidrug therapy, drug interactions are important considerations in designing effective and tolerable regimens. Clarithromycin has had a significant impact on the treatment of disseminated Mycobacterium avium complex infection, and zidovudine is the best-studied and one of the most widely used antiretroviral agents in this population. We conducted a study to determine the maximally tolerated dose of clarithromycin and the pharmacokinetics of clarithromycin and zidovudine individually and in combination. Mixing studies were conducted to simulate potential interaction in the gastric environment. The simultaneous administration of zidovudine and clarithromycin had little impact on the pharmacokinetics of clarithromycin or of its major metabolite. However, coadministration of zidovudine and clarithromycin at three doses (500 mg orally [p.o.] twice daily [b.i.d.], 1,000 mg p.o. b.i.d., and 2,000 mg p.o. b.i.d.) reduced the maximum concentration of zidovudine by 41% (P < 0.005) and the area under the concentration-time curve from 0 to 4 h for zidovudine by 25% (P < 0.05) and increased the time to maximum concentration of zidovudine by 84% (P < 0.05), compared with zidovudine administered alone. Mixing studies did not detect the formation of insoluble complexes due to chelation, suggesting that the decrease in zidovudine concentrations results from some other mechanism. Simultaneous administration of zidovudine and clarithromycin appears to decrease the levels of zidovudine in serum, and it may be advisable that these drugs not be given at the same time. Drug interactions should be carefully evaluated in persons with advanced human immunodeficiency virus infection who are receiving multiple pharmacologic agents.     

Clinical pharmacokinetics of 3'-azido-3'-deoxythymidine (zidovudine) and catabolites with formation of a toxic catabolite, 3'-amino-3'-deoxythymidine.

This study investigated pharmacokinetics and metabolism of 3'-azido-3'-deoxythymidine (zidovudine) in patients after a 1-hour intravenous infusion of 2.5 mg/kg zidovudine with a radiolabeled tracer amount of [5-3H]-zidovudine. In addition to unchanged drug and its 5'-O-glucuronide (zidovudine glucuronide), two novel catabolites of zidovudine were detected as 3'-amino-3'-deoxythymidine (AMT), and its 5'-O-glucuronide (GAMT). The AMT apparent plasma elimination half-life (2.70 +/- 0.7 hours) was longer than that of zidovudine (1.20 +/- 0.30 hours) and zidovudine glucuronide (1.60 +/- 0.5 hours). The zidovudine/AMT plasma peak concentration and area under the concentration-time curve ratios were approximately 8 and 5, respectively. Urinary recovery of radioactivity was essentially complete within 24 hours. AMT glucuronide was not detected in urine or plasma, and only low levels of this catabolite were detected in bile. In contrast, AMT was not detected in bile. The substantial levels of AMT in the plasma of patients after zidovudine administration suggests that this catabolite may affect the pharmacodynamic properties of zidovudine in relation to its activity against human immunodeficiency virus replication and cytotoxicity to host cells.     

Activity of the new triazole derivative albaconazole against Trypanosoma (Schizotrypanum) cruzi in dog hosts

Albaconazole is an experimental triazole derivative with potent and broad-spectrum antifungal activity and a remarkably long half-life in dogs, monkeys, and humans. In the present work, we investigated the in vivo activity of this compound against two strains of the protozoan parasite Trypanosoma (Schizotrypanum) cruzi, the causative agent of Chagas' disease, using dogs as hosts. The T. cruzi strains used in the study were previously characterized (murine model) as susceptible (strain Berenice-78) and partially resistant (strain Y) to the drugs currently in clinical use, nifurtimox and benznidazole. Our results demonstrated that albaconazole is very effective in suppressing the proliferation of the parasite and preventing the death of infected animals. Furthermore, the parasitological, PCR, serological, and proliferative assay results indicated parasitological cure indices of 25 and 100% among animals inoculated with T. cruzi strain Y when they were treated with albaconazole at 1.5 mg/kg of body weight/day for 60 and 90 days, respectively. On the other hand, although albaconazole given at 1.5 mg/kg/day was very effective in suppressing the proliferation of the parasite in animals infected with the Berenice-78 T. cruzi strain, no parasitological cure was observed among them, even when a longer treatment period (150 doses) was used. In conclusion, our results demonstrate that albaconazole has trypanocidal activity in vivo and is capable of inducing radical parasitological cure, although natural resistance to this compound was also indicated. Furthermore, the compound can be used in long-term treatment schemes (60 to 150 days) with minimal toxicity and thus represents a potentially useful candidate for the treatment of human Chagas' disease.     

Long-term tolerance and efficacy of 3'-azidothymidine and 3'-fluorothymidine treatment of asymptomatic monkeys infected with simian immunodeficiency virus.

Macaques chronically infected with simian immunodeficiency virus were treated with zidovudine (20 mg/kg of body weight per day for 9 weeks) or 3'-fluorothymidine (5 mg/kg of body weight per day for 9 weeks or three doses of 2 mg/kg per day for 24 days). Hematological changes in the treated animals included macrocytic anemia and leukopenia. Determination of antiviral effects in this model requires improved assay methods.     

Penetration of zidovudine and 3''-fluoro-3''-deoxythymidine into the brain, muscle tissue, and veins in cynomolgus monkeys: relation to antiviral action.

Cynomolgus monkeys had microdialysis probes implanted under ketamine anesthesia into peripheral veins, thigh muscles, and the brain in order to sample the extracellular fluid for the concentrations of unbound nucleoside analogs. A dose of 25 mg of zidovudine or 3'-fluoro-3'-deoxythymidine (FLT) per kg was administered subcutaneously to each of three animals. Relatively high antiviral concentrations of FLT and zidovudine were present in peripheral tissues and in the brain. It was found that the concentration of zidovudine in the brain was approximately one-third of that in muscle and veins; the same relation was observed for FLT. The in vivo unbound concentrations of both drugs in the brain, muscle, and venous blood exceeded those reported to inhibit human immunodeficiency virus replication in vitro. In addition, in a correlative study we found that the appearance of p24 antigen in sera of monkeys infected with simian immunodeficiency virus was significantly delayed by both compounds (15 mg/kg three times daily for 9 days after infection). Thus, we have shown that the extracellular concentrations of unbound FLT and zidovudine in the brain and peripheral tissues attained with in vivo antiviral doses exceed in vitro antiviral concentrations.     

Fluorescence polarization immunoassay for zidovudine.

We report a fluorescence polarization immunoassay (FPIA) for zidovudine (azidothymidine; Retrovir). This assay is accurate and specific over the clinically relevant range of zidovudine concentrations in serum (from 1 to 1,250 ng/ml; from 0.004 to 4.8 microM) and is unaffected by potentially interfering compounds in the sera of patients with renal or hepatic failure. Cross-reactivity with structural analogs of zidovudine (including zidovudine glucuronide) is less than 0.05%, except for cross-reactivities of 0.2, 0.3, and 0.4% with 3-methylthymidine, 3',5'-dideoxythymidine, and A22U (the optical isomer of zidovudine), respectively. The FPIA for zidovudine is more sensitive and more specific than high-performance liquid chromatography (HPLC); it requires 50 to 60 or 200 versus 500 microliters of serum and is faster to perform (45 specimens per h with the FPIA versus 3 specimens per h with HPLC). The zidovudine FPIA compares well with the radioimmunoassay. A correlation coefficient of 0.992 was observed with 31 serum specimens examined by both methods. All three assays (FPIA, radioimmunoassay, and HPLC) are unaffected by the heat treatment used to inactivate human immunodeficiency virus. The zidovudine FPIA should be particularly useful for analyzing specimens from large numbers of human immunodeficiency virus-infected patients receiving zidovudine in current clinical trials.     

L-tryptophan implicated in human eosinophilia-myalgia syndrome causes fasciitis and perimyositis in the Lewis rat.

Tryptophan-associated eosinophilia-myalgia syndrome (L-TRP-EMS) is a newly described syndrome which occurred in epidemic fashion in the United States in the summer and fall of 1989. Epidemiologic data has linked the syndrome to intake of L-tryptophan (L-TRP) from one specific manufacturer, but the precise etiologic compound(s) must be established by replication of the syndrome in an appropriate animal model. In this study, implicated L-TRP, United States Pharmacopeia (USP) grade L-TRP, or vehicle was administered by gavage in a blinded fashion for 38 d to female Lewis rats at doses comparable with those ingested by patients who developed the eosinophilia-myalgia syndrome. Animals receiving implicated L-TRP, but not those receiving USP grade L-TRP or vehicle, developed histologic signs consistent with fasciitis and perimyositis, specific pathologic features of human L-TRP-EMS. Peripheral blood eosinophilia was not observed. Hypothalamic corticotropin releasing hormone mRNA levels were lower and plasma corticosterone levels tended to be lower in the animals that received implicated L-TRP. Plasma L-kynurenine was higher in both L-TRP-treated groups compared to the vehicle-treated animals. The female Lewis rat is known to be susceptible to a wide variety of inflammatory diseases. Identification of specific inflammatory changes in this rat following exposure to implicated L-TRP indicates that this animal model will be important in subsequent investigations into the etiology, pathogenesis, and treatment of human L-TRP-EMS.     

Prevention of doxorubicin cardiac toxicity in the mouse by N-acetylcysteine.

This study was undertaken to investigate the effect of exogenous sulfhydryl compound administration on the toxicity of doxorubicin in mice. Pretreatment of CDF1 mice with a pharmacologic dose (2,000 mg/kg) of n-acetyl-l-cysteine 1 h before doxorubicin (20 mg/kg, i.p.) decreased lethality from 100% (n = 44) to 37.7% (n = 53), P less than 0.001. Variation in the timing and dose of n-acetylcysteine significantly diminished its protective activity. Pretreatment with n-acetylcysteine also significantly reduced long-term mortality in animals receiving multiple doses of doxorubicin; 10 wk after the third of three doxorubicin doses (5 mg/kg, i.p.) administered at 2-wk intervals, survival in the n-acetylcysteine pretreated group was 51.4% (n = 35) compared with 16.7% (n = 30) for animals receiving saline before doxorubicin, P less than 0.01. In this experiment, n-acetylcysteine pretreatment also diminished doxorubicin-related losses in total body weight and heart wet weight by 55.2% (P less than 0.05), and 60.9% (P less than 0.02), respectively, compared with animals pretreated with saline. N-acetylcysteine pretreatment also ablated electron microscopic evidence of doxorubicin cardiomyopathy without alleviating morphological features of its toxic effects on the liver or small intestinal mucosa. The cardioprotective action of n-acetylcysteine may be partially explained by the 429 +/- 60% increase in cardiac nonprotein sulfhydryl content (P less than 0.01) that was measured one hour after n-acetylcysteine administration; nonprotein sulfhydryl concentration in the liver at the same time was insignificantly different from control levels. Treatment with n-acetylcysteine also increased the nonprotein sulfhydryl content of P388 leukemia cells nearly threefold; however, it did not after the chemotherapeutic activity of doxorubicin against this murine tumor. Whereas n-acetylcysteine blocked doxorubicin cardiac toxicity, it did not affect the uptake or metabolism of doxorubicin in the heart or liver. These results suggest that the concentration of free sulfhydryl groups in the heart may play a role in the development of doxorubicin cardiac toxicity and that augmenting cardiac nonprotein sulfhydryl group content with n-acetylcysteine may provide a means to enhance the chemotherapeutic index of doxorubicin.     

Mitochondrial myopathy associated with chronic zidovudine therapy in AIDS

One hundred and eighteen consecutively identified AIDS patients,88 of whom received zidovudine (1000–1200 mg/day), werefollowed for 1 year to investigate prospectively the relationshipbetween zidovudine and myopathy. Clinical and biochemical evidenceof proximal myopathy was seen in 7 of 41 patients (17%) whohad been receiving zidovudine for more than 270 days, but innone of those on short-term therapy and in none of the controls.Serum creatine kinase levels rose a mean of 76 days (range 34–187)before the onset of clinical signs. Creatine kinase returnedto normal within 4 weeks of cessation of zidovudine and strengthreturned within 8 weeks, though loss of muscle bulk persisted.Chronic malaise, anorexia and nausea accompanied the myopathyand remitted remitted within 8 weeks of stopping zidovudine.Muscle histology in four patients with myopathy showed fibresize variation with atrophic, necrotic and degenerating fibresand an absence of inflammation. Ultrastructural studies showedglycogenpacked sarcoplasm, lipid droplets and grossly abnormalgiant mitochondria. These abnormalities improved substantiallyafter stopping zidovudine. Similar but less marked changes wereseen in a zidovudine treated patient without myopathy, but wereabsent in one AIDS patient not taking the drug. Long-term zidovudinetherapy is associated with a mitochondrial myopathy and theconstitutional features suggest that it is part of a wider disorderaffecting cellular function in other tissues.     

Efficacy of amikacin and ceftazidime in experimental aortic valve endocarditis due to Pseudomonas aeruginosa.

The in vivo efficacies of amikacin, ceftazidime, and their combination were evaluated in experimental aortic valve endocarditis due to Pseudomonas aeruginosa. Eighty catheterized rabbits were infected with a P. aeruginosa strain susceptible to both amikacin and ceftazidime and then received no therapy (controls), amikacin (15 mg/kg per day), ceftazidime (100 mg/kg per day), or amikacin-ceftazidime. Amikacin-ceftazidime significantly lowered vegetation titers of P. aeruginosa at day 7 of therapy versus other regimens (P less than 0.0005). However, by day 14 of therapy, vegetation titers in animals receiving amikacin or ceftazidime regimens or both were not different from those of untreated controls; this was associated with in vivo development of amikacin resistance in most infected vegetations (79%), a phenomenon not seen at day 7 of therapy. Amikacin resistance was unstable in vivo, being undetectable in vegetations examined 5 days after treatment with amikacin had been completed. In contrast, ceftazidime resistance (first noted at day 7 of therapy in 12% of vegetations) persisted after termination of treatment with this agent. These in vivo observations on loss of amikacin resistance and persistence of ceftazidime resistance were mirrored during in vitro passage studies of amikacin- or ceftazidime-resistant P. aeruginosa strains isolated from cardiac vegetations. Amikacin resistance was no longer detectable by passage 5 in antibiotic-free media; however, ceftazidime resistance was stable despite 15 such passages. In vivo development of aminoglycoside-beta-lactam resistances was associated with poor bacteriologic efficacy in this model.