In patients with chronic hepatitis B, treatment with fialuridine induced a severe toxic reaction characterized by hepatic failure, lactic acidosis, pancreatitis, neuropathy, and myopathy. This toxic reaction was probably caused by widespread mitochondrial damage and may occur infrequently with other nucleoside analogues.

To determine if ciprofloxacin therapy alters the response to warfarin treatment, 36 adult patients attending three university-affiliated outpatient anticoagulation clinics randomly received a 12-day course of ciprofloxacin (750 mg twice daily) and a 12-day course of placebo; each course was separated by a 2-week washout period. Prothrombin times (PTs), concentrations of S-warfarin and R-warfarin (the isomers of warfarin), and concentrations of clotting factors II and VII were determined three times weekly for 9 weeks. By day 12 of ciprofloxacin therapy, concentrations of S-warfarin remained unchanged compared with those after placebo therapy, but R-warfarin concentrations increased significantly (1.15 times those after placebo therapy; P = .001); concentrations of clotting factors II and VII decreased (0.903 and 0.872 times those after placebo therapy, respectively, P < or = .020). The mean PT ratio after 12 days of ciprofloxacin therapy increased slightly (1.032 times that after placebo therapy; P = .057), but no patient had bleeding or a change in PT that required alteration in warfarin or ciprofloxacin therapy. We conclude that warfarin therapy is not a contraindication to the use of ciprofloxacin.

The purpose of the present study was to assess the cutaneous response to intradermally administered vancomycin in healthy adults and to determine whether the magnitude of the cutaneous response correlated to the severity of "red man syndrome" (RMS) following intravenous administration of vancomycin to the same subjects. Eleven healthy males were skin tested with intradermally administered histamine and saline controls and intradermally administered vancomycin at different concentrations. Vancomycin caused a dose-dependent area of flare in all subjects. The sigmoidal maximal flare model was used to fit each dose-response curve, and cutaneous responsiveness to vancomycin was quantified by various methods, including the flare area at each dose, maximum flare area (maximal flare), dose required to produce 50%o of maximum flare, dose required to produce a flare area of 400 mm2, and the slope of the dose-response curve. One week after skin testing, subjects received an infusion of vancomycin, 15 mg/kg of body weight over 60 min. For the assessment of the severity of RMS, we used previously described methods. Although all subjects experienced erythema from the intravenously administered vancomycin and 10 subjects had pruritus, there was no significant correlation between vancomycin skin test results and the severity of RMS. We conclude that vancomycin skin tests do not predict the severity of RMS. In addition, vancomycin skin tests may be of no benefit for assessing immunoglobulin E-mediated allergy to vancomycin, since all subjects had a positive reaction at concentrations of 210 Fg/ml.The most common adverse effect of vancomycin is "red man syndrome" (RMS), which is characterized by flushing and itching, especially of the upper torso (23). In severe cases, hypotension may occur. These signs and symptoms result from the nonimmunologic release of histamine, and the severity is proportional to the amount of histamine released (24). The source of histamine is believed to be primarily cutaneous mast cells, and vancomycin has been shown to result in mast cell degranulation in vitro (15). The frequency of RMS is largely determined by dose and infusion time. In healthy volunteers who receive 1 g as a 60-min infusion, the frequency is 80 to 90% (23). The frequency of RMS in infected patients who receive vancomycin (1 g over 60 min) varies from <10 to 50% in prospective studies (25,28). RMS may be prevented in most patients by a reduction in the dose or the rate of infusion or by premedication with antihistamines (23).In normal volunteers, the severity of RMS varies widely, despite administration of identical doses (24). The reason for this large difference in susceptibility to vancomycin toxicity is unknown, but it probably reflects between-subject differences in histamine release. We reasoned that if vancomycin causes a direct release of histamine by degranulation of cutaneous mast cells, then intracutaneous administration of vancomycin should produce a dose-related weal-and-flare * Corresponding author. t Present address:

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