D. Debruyne
Jul 1, 1997
Citations
3
Influential Citations
133
Citations
Quality indicators
Journal
Clinical Pharmacokinetics
Abstract
SummaryThe bis triazole agent fluconazole is used widely in the treatment of superficial and deep mycoses. A single oral dose of fluconazole 150mg gives a mean long term clinical cure rate of 84 ± 5% and is considered a valuable alternative to other topical antifungal drugs for vaginal candidiasis. A clinical cure rate of 90.4% for oropharyngeal candidiasis was obtained with 100mg daily for a minimum of 14 days; however, as for the other azoles the rate of relapse was large (40%) in immunocompromised patients. A daily dose of 100mg for at last 3 weeks gave satisfying outcomes for oesophageal candidiasis. Most patients (71 to 86%) with signs and symptoms of urinary tract candidiasis show beneficial clinical results when given oral fluconazole 50mg for several weeks. Fluconazole 50 to 150mg given for weeks or months results in over 90% clinical cure or improvement for cutaneous mycosis including tinea, pityriasis, cryptococcosis and candidiasis. Prolonged (6 to 12 months) fluconazole 150mg once a week is needed to treat onychomycosis successfully. Higher oral doses (200 to 400mg daily) for long periods are generally used to treat deep mycoses such as meningitis, ophthalmias, pneumonia, hepatosplenic mycosis and endocarditis. Fluconazole is effective for treating the fungal peritonitis which can complicate continuous ambulatory peritoneal dialysis (CAPD). A regimen of 50mg intraperitoneally or 100mg orally was used in these patients with impaired renal function. The dosage schedules used to treat disseminated fungal infections due to systemic mycoses with different or multiple foci of infections vary widely, with doses of 50 to 400mg given orally or intravenously for between 1 week and several months. The most recent clinical reports have investigated the use of prophylaxis with fluconazole 100 to 400mg daily, in immunocompromised patients.Fluconazole is found in body fluids such as vaginal secretions, breast milk, saliva, sputum and cerebrospinal fluid at concentrations comparable with those determined in blood after single or multiple doses. There is an excellent linear plasma concentration-dose relationship, but the mycological and clinical responses do not appear to be well correlated with the dose.A total maximum daily dose of 1600mg is recommended to avoid neurological toxicity. Data from pharmacokinetic studies conducted in patients, mainly those with AIDS, and using a 1-compartment model give very constant parameters similar to those obtained in healthy individuals. Bioavailability, measured in HIV-positive patients and those with AIDS, exceeded 93% for tablets, suspension and suppositories. The time to reach peak plasma concentrations (tmax) was 2.4 to 3.7 hours. The peak plasma drug concentration (Cmax) obtained after a 100mg oral dose was 2 mg/L. Areas under the concentration-time curve (AUC) obtained in different studies all correlate well with the dose (r=0.926). The AUC determined after 200 and 25mg suppositories were similarly well correlated.Hypochlorhydria does not affect the absorption of fluconazole, neither does food intake, race (Japanese or Caucasian) or gastrointestinal resection. Binding to plasma protein is low (11.14%) and is increased to 23% in cancer patients.Fluconazole is rapidly distributed to the tissue, where it accumulates. Tissues fall into 1 of 4 groups of increasing drug concentration: blood, bone and brain have the lowest concentrations, and spleen has the highest. The volume of distribution (Vd) remains stable at 46.3 ± 7.9L and is considered to be an ‘invariant’ parameter across species.Fluconazole is poorly metabolised and is mainly eliminated unchanged in the urine. The percentage of the dose recovered in the urine in 48 hours is close to 60%. Concentrations in the urine are high and the half-life (t½) is long (37.2 ± 5.5h) in patients, mainly those with AIDS, which is not significantly different from the t½ (31.4 ± 4.7 hours) in healthy individuals. The mean total clearance is 1.073 ± 0.473 L/h and renal clearance is 72% of the total clearance.The pharmacokinetics of fluconazole are different in infants (larger Vd and shorter t½) so that the fluconazole dosage must be adjusted accordingly. Absorption is rapid and nearly complete, but intravenous administration is preferred for neonates. The Cmax and AUC0→∞ vary linearly with the dose, and tmax is 1 to 2 hours. The mean Vd is 1.15 ± 0.52 L/kg; it is largest in neonates and decreases in young adult to a value similar to that in adults. The mean t½ is very long (71 ±417 hours) in premature and neonates and is correlated with age during the first weeks of life. It stabilises to around 21.2 ± 5.1 hours during the first years of life, shorter than in adults. Renal clearance is 65 ± 5% of total clearance.t½ increases with decreasing renal function in renal disease. It is 124.6 to 98.1 hours in patients with end-stage renal failure and the dose must be decreased by 50% or the interval between doses extended 2- to 3-fold. In patients on CAPD the t½ (79 ± 7 hours) is intermediate between those reported in patients with or without renal disease and a 150mg dose is needed in a single dialysate bag every 48 hours. The t½ does not change in haemodialysis epuration mode and the dose given at the end of dialysis need not be changed.Fluconazole increases the concentrations of glipizide, glyburide, midazolam, nortriptyline, phenytoin, rifabutin, tacrolimus, tolbutamide and cyclosporin at doses over 200mg daily. Cimetidine and rifampicin (rifampin) decrease the concentrations of fluconazole.