Pharmacokinetics and Metabolism
The pharmacokinetic properties of fluconazole are similar following administration by the intravenous or oral routes. In normal volunteers, the bioavailability of orally administered fluconazole is over 90% compared with intravenous administration. Bioequivalence was established between the 100 mg tablet and both suspension strengths when administered as a single 200 mg dose.
Peak plasma concentrations (Cmax) in fasted normal volunteers occur between 1 and 2 hours with a terminal plasma elimination half-life of approximately 30 hours (range: 20-50 hours) after oral administration.
In fasted normal volunteers, administration of a single oral 400 mg dose of DIFLUCAN (fluconazole) leads to a mean Cmax of 6.72 µg/mL (range: 4.12 to 8.08 µg/mL) and after single oral doses of 50-400 mg, fluconazole plasma concentrations and AUC (area under the plasma concentration-time curve) are dose proportional.
Administration of a single oral 150 mg tablet of DIFLUCAN (fluconazole) to ten lactating women resulted in a mean Cmax of 2.61 µg/mL (range: 1.57 to 3.65 µg/mL).
Steady-state concentrations are reached within 5-10 days following oral doses
of 50-400 mg given once daily. Administration of a loading dose (on day 1) of
twice the usual daily dose results in plasma concentrations close to steady-state
by the second day. The apparent volume of distribution of fluconazole approximates
that of total body water. Plasma protein binding is low (11-12%). Following
either single- or multiple-oral doses for up to 14 days, fluconazole penetrates
into all body fluids studied (see table below). In normal volunteers,
saliva concentrations of fluconazole were equal to or slightly greater than
plasma concentrations regardless of dose, route, or duration of dosing. In patients
with bronchiectasis, sputum concentrations of fluconazole following a single
150 mg oral dose were equal to plasma concentrations at both 4 and 24 hours
post dose. In patients with fungal meningitis, fluconazole concentrations in
the CSF are approximately 80% of the corresponding plasma concentrations.
A single oral 150 mg dose of fluconazole administered to 27 patients penetrated into vaginal tissue, resulting in tissue:plasma ratios ranging from 0.94 to 1.14 over the first 48 hours following dosing.
A single oral 150 mg dose of fluconazole administered to 14 patients penetrated into vaginal fluid, resulting in fluid:plasma ratios ranging from 0.36 to 0.71 over the first 72 hours following dosing.
| Tissue or Fluid |
Ratio of Fluconazole Tissue (Fluid)/Plasma
Concentration* |
| Cerebrospinal fluid† |
0.5-0.9 |
| Saliva |
1 |
| Sputum |
1 |
| Blister fluid |
1 |
| Urine |
10 |
| Normal skin |
10 |
| Nails |
1 |
| Blister skin |
2 |
| Vaginal tissue |
1 |
| Vaginal fluid |
0.4-0.7 |
* Relative to concurrent concentrations in plasma in subjects
with normal renal function.
† Independent of degree of meningeal inflammation. |
In normal volunteers, fluconazole is cleared primarily by renal excretion, with approximately 80% of the administered dose appearing in the urine as unchanged drug. About 11% of the dose is excreted in the urine as metabolites.
The pharmacokinetics of fluconazole are markedly affected by reduction in renal
function. There is an inverse relationship between the elimination half-life
and creatinine clearance. The dose of DIFLUCAN may need to be reduced in patients
with impaired renal function. (See DOSAGE AND ADMINISTRATION.)
A 3-hour hemodialysis session decreases plasma concentrations by approximately
50%.
In normal volunteers, DIFLUCAN administration (doses ranging from 200 mg to 400 mg once daily for up to 14 days) was associated with small and inconsistent effects on testosterone concentrations, endogenous corticosteroid concentrations, and the ACTH-stimulated cortisol response.
Pharmacokinetics in Children
In children, the following pharmacokinetic data {Mean(%cv)} have been reported:
| Age Studied |
Dose
(mg/kg) |
Clearance
(mL/min/kg) |
Half-life
(Hours) |
Cmax
(µg/mL) |
Vdss
(L/kg) |
| 9 Months-13 years |
Single-Oral 2 mg/kg |
0.40 (38%)
N=14 |
25.0 |
2.9 (22%)
N=16 |
___ |
| 9 Months-13 years |
Single-Oral 8 mg/kg |
0.51 (60%)
N=15 |
19.5 |
9.8 (20%)
N=15 |
___ |
| 5-15 years |
Multiple IV 2 mg/kg |
0.49 (40%)
N=4 |
17.4 |
5.5 (25%)
N=5 |
0.722 (36%)
N=4 |
| 5-15 years |
Multiple IV 4 mg/kg |
0.59 (64%)
N=5 |
15.2 |
11.4 (44%)
N=6 |
0.729 (33%)
N=5 |
| 5-15 years |
Multiple IV 8 mg/kg |
0.66 (31%)
N=7 |
17.6 |
14.1 (22%)
N=8 |
1.069 (37%)
N=7 |
Clearance corrected for body weight was not affected by age in these studies. Mean body clearance in adults is reported to be 0.23 (17%) mL/min/kg.
In premature newborns (gestational age 26 to 29 weeks), the mean (%cv) clearance within 36 hours of birth was 0.180 (35%, N=7) mL/min/kg, which increased with time to a mean of 0.218 (31%, N=9) mL/min/kg six days later and 0.333 (56%, N=4) mL/min/kg 12 days later. Similarly, the half-life was 73.6 hours, which decreased with time to a mean of 53.2 hours six days later and 46.6 hours 12 days later.
Pharmacokinetics in Elderly
A pharmacokinetic study was conducted in 22 subjects, 65 years of age or older receiving a single 50 mg oral dose of fluconazole. Ten of these patients were concomitantly receiving diuretics. The Cmax was 1.54 mcg/mL and occurred at 1.3 hours post dose. The mean AUC was 76.4+ 20.3 mcg·h/mL, and the mean terminal half-life was 46.2 hours. These pharmacokinetic parameter values are higher than analogous values reported for normal young male volunteers. Coadministration of diuretics did not significantly alter AUC or Cmax. In addition, creatinine clearance (74 mL/min), the percent of drug recovered unchanged in urine (0-24 hr, 22%) and the fluconazole renal clearance estimates (0.124 mL/min/kg) for the elderly were generally lower than those of younger volunteers. Thus, the alteration of fluconazole disposition in the elderly appears to be related to reduced renal function characteristic of this group. A plot of each subject's terminal elimination half-life versus creatinine clearance compared with the predicted half-life – creatinine clearance curve derived from normal subjects and subjects with varying degrees of renal insufficiency indicated that 21 of 22 subjects fell within the 95% confidence limit of the predicted half-life – creatinine clearance curves. These results are consistent with the hypothesis that higher values for the pharmacokinetic parameters observed in the elderly subjects compared with normal young male volunteers are due to the decreased kidney function that is expected in the elderly.
Drug Interaction Studies
Oral contraceptives: Oral contraceptives were administered as
a single dose both before and after the oral administration of DIFLUCAN 50 mg
once daily for 10 days in 10 healthy women. There was no significant difference
in ethinyl estradiol or levonorgestrel AUC after the administration of 50 mg
of DIFLUCAN. The mean increase in ethinyl estradiol AUC was 6% (range: –47 to
108%) and levonorgestrel AUC increased 17% (range: –33 to 141%).
In a second study, twenty-five normal females received daily doses of both 200 mg DIFLUCAN tablets or placebo for two, ten-day periods. The treatment cycles were one month apart with all subjects receiving DIFLUCAN during one cycle and placebo during the other. The order of study treatment was random. Single doses of an oral contraceptive tablet containing levonorgestrel and ethinyl estradiol were administered on the final treatment day (day 10) of both cycles. Following administration of 200 mg of DIFLUCAN, the mean percentage increase of AUC for levonorgestrel compared to placebo was 25% (range: -12 to 82%) and the mean percentage increase for ethinyl estradiol compared to placebo was 38% (range: -11 to 101%). Both of these increases were statistically significantly different from placebo.
A third study evaluated the potential interaction of once weekly dosing of fluconazole 300 mg to 21 normal females taking an oral contraceptive containing ethinyl estradiol and norethindrone. In this placebo-controlled, double-blind, randomized, two-way crossover study carried out over three cycles of oral contraceptive treatment, fluconazole dosing resulted in small increases in the mean AUCs of ethinyl estradiol and norethindrone compared to similar placebo dosing. The mean AUCs of ethinyl estradiol and norethindrone increased by 24% (95% C.I. range 18-31%) and 13% (95% C.I. range 8-18%), respectively relative to placebo. Fluconazole treatment did not cause a decrease in the ethinyl estradiol AUC of any individual subject in this study compared to placebo dosing. The individual AUC values of norethindrone decreased very slightly ( < 5%) in 3 of the 21 subjects after fluconazole treatment.
Cimetidine: DIFLUCAN 100 mg was administered as a single oral
dose alone and two hours after a single dose of cimetidine 400 mg to six healthy
male volunteers. After the administration of cimetidine, there was a significant
decrease in fluconazole AUC and Cmax. There was a mean ± SD decrease
in fluconazole AUC of 13% ± 11% (range: –3.4 to –31%) and Cmax decreased
19% ± 14% (range: –5 to –40%). However, the administration of cimetidine
600 mg to 900 mg intravenously over a four-hour period (from one hour before
to 3 hours after a single oral dose of DIFLUCAN 200 mg) did not affect the bioavailability
or pharmacokinetics of fluconazole in 24 healthy male volunteers.
Antacid: Administration of Maalox® (20 mL) to 14 normal male
volunteers immediately prior to a single dose of DIFLUCAN 100 mg had no effect
on the absorption or elimination of fluconazole.
Hydrochlorothiazide: Concomitant oral administration of 100 mg
DIFLUCAN and 50 mg hydrochlorothiazide for 10 days in 13 normal volunteers resulted
in a significant increase in fluconazole AUC and Cmax compared to DIFLUCAN given
alone. There was a mean ± SD increase in fluconazole AUC and Cmax of
45% ± 31% (range: 19 to 114%) and 43% ± 31% (range: 19 to 122%),
respectively. These changes are attributed to a mean ± SD reduction in
renal clearance of 30% ± 12% (range: –10 to –50%).
Rifampin: Administration of a single oral 200 mg dose of DIFLUCAN
after 15 days of rifampin administered as 600 mg daily in eight healthy male
volunteers resulted in a significant decrease in fluconazole AUC and a significant
increase in apparent oral clearance of fluconazole. There was a mean ±
SD reduction in fluconazole AUC of 23% ± 9% (range: –13 to –42%). Apparent
oral clearance of fluconazole increased 32% ± 17% (range: 16 to 72%).
Fluconazole half-life decreased from 33.4 ± 4.4 hours to 26.8 ±
3.9 hours. (See PRECAUTIONS.)
Warfarin: There was a significant increase in prothrombin time
response (area under the prothrombin time-time curve) following a single dose
of warfarin (15 mg) administered to 13 normal male volunteers following oral
DIFLUCAN 200 mg administered daily for 14 days as compared to the administration
of warfarin alone. There was a mean ± SD increase in the prothrombin
time response (area under the prothrombin time-time curve) of 7% ± 4%
(range: –2 to 13%). (See PRECAUTIONS.) Mean
is based on data from 12 subjects as one of 13 subjects experienced a 2-fold
increase in his prothrombin time response.
Phenytoin: Phenytoin AUC was determined after 4 days of phenytoin
dosing (200 mg daily, orally for 3 days followed by 250 mg intravenously for
one dose) both with and without the administration of fluconazole (oral DIFLUCAN
200 mg daily for 16 days) in 10 normal male volunteers. There was a significant
increase in phenytoin AUC. The mean ± SD increase in phenytoin AUC was
88% ± 68% (range: 16 to 247%). The absolute magnitude of this interaction
is unknown because of the intrinsically nonlinear disposition of phenytoin.
(See PRECAUTIONS.)
Cyclosporine: Cyclosporine AUC and Cmax were determined before
and after the administration of fluconazole 200 mg daily for 14 days in eight
renal transplant patients who had been on cyclosporine therapy for at least
6 months and on a stable cyclosporine dose for at least 6 weeks. There was a
significant increase in cyclosporine AUC, Cmax, Cmin (24-hour concentration),
and a significant reduction in apparent oral clearance following the administration
of fluconazole. The mean ± SD increase in AUC was 92% ± 43% (range:
18 to 147%). The Cmax increased 60% ± 48% (range: –5 to 133%). The Cmin
increased 157% ± 96% (range: 33 to 360%). The apparent oral clearance
decreased 45% ± 15% (range: –15 to –60%). (See PRECAUTIONS.)
Zidovudine: Plasma zidovudine concentrations were determined
on two occasions (before and following fluconazole 200 mg daily for 15 days)
in 13 volunteers with AIDS or ARC who were on a stable zidovudine dose for at
least two weeks. There was a significant increase in zidovudine AUC following
the administration of fluconazole. The mean ± SD increase in AUC was
20% ± 32% (range: –27 to 104%). The metabolite, GZDV, to parent drug
ratio significantly decreased after the administration of fluconazole, from
7.6 ± 3.6 to 5.7 ± 2.2.
Theophylline: The pharmacokinetics of theophylline were determined
from a single intravenous dose of aminophylline (6 mg/kg) before and after the
oral administration of fluconazole 200 mg daily for 14 days in 16 normal male
volunteers. There were significant increases in theophylline AUC, Cmax, and
half-life with a corresponding decrease in clearance. The mean ± SD theophylline
AUC increased 21% ± 16% (range: –5 to 48%). The Cmax increased 13% ±
17% (range: –13 to 40%). Theophylline clearance decreased 16% ± 11% (range:
–32 to 5%). The half-life of theophylline increased from 6.6 ± 1.7 hours
to 7.9 ± 1.5 hours. (See PRECAUTIONS.)
Terfenadine: Six healthy volunteers received terfenadine 60 mg
BID for 15 days. Fluconazole 200 mg was administered daily from days 9 through
15. Fluconazole did not affect terfenadine plasma concentrations. Terfenadine
acid metabolite AUC increased 36% ± 36% (range: 7 to 102%) from day 8
to day 15 with the concomitant administration of fluconazole. There was no change
in cardiac repolarization as measured by Holter QTc intervals. Another study
at a 400-mg and 800-mg daily dose of fluconazole demonstrated that DIFLUCAN
taken in doses of 400 mg per day or greater significantly increases plasma levels
of terfenadine when taken concomitantly. (See CONTRAINDICATIONS
and PRECAUTIONS.)
Oral hypoglycemics: The effects of fluconazole on the pharmacokinetics
of the sulfonylurea oral hypoglycemic agents tolbutamide, glipizide, and glyburide
were evaluated in three placebo-controlled studies in normal volunteers. All
subjects received the sulfonylurea alone as a single dose and again as a single
dose following the administration of DIFLUCAN 100 mg daily for 7 days. In these
three studies 22/46 (47.8%) of DIFLUCAN treated patients and 9/22 (40.1%) of
placebo treated patients experienced symptoms consistent with hypoglycemia.
(See PRECAUTIONS.)
Tolbutamide: In 13 normal male volunteers, there was significant
increase in tolbutamide (500 mg single dose) AUC and Cmax following the administration
of fluconazole. There was a mean ± SD increase in tolbutamide AUC of
26% ± 9% (range: 12 to 39%). Tolbutamide Cmax increased 11% ±
9% (range: –6 to 27%). (See PRECAUTIONS.)
Glipizide: The AUC and Cmax of glipizide (2.5 mg single dose)
were significantly increased following the administration of fluconazole in
13 normal male volunteers. There was a mean ± SD increase in AUC of 49%
± 13% (range: 27 to 73%) and an increase in Cmax of 19% ± 23%
(range: –11 to 79%). (See PRECAUTIONS.)
Glyburide: The AUC and Cmax of glyburide (5 mg single dose) were
significantly increased following the administration of fluconazole in 20 normal
male volunteers. There was a mean ± SD increase in AUC of 44% ±
29% (range: –13 to 115%) and Cmax increased 19% ± 19% (range: –23 to
62%). Five subjects required oral glucose following the ingestion of glyburide
after 7 days of fluconazole administration. (See PRECAUTIONS.)
Rifabutin: There have been published reports that an interaction
exists when fluconazole is administered concomitantly with rifabutin, leading
to increased serum levels of rifabutin. (See PRECAUTIONS.)
Tacrolimus: There have been published reports that an interaction
exists when fluconazole is administered concomitantly with tacrolimus, leading
to increased serum levels of tacrolimus. (See PRECAUTIONS.)
Cisapride: A placebo-controlled, randomized, multiple-dose study
examined the potential interaction of fluconazole with cisapride. Two groups
of 10 normal subjects were administered fluconazole 200 mg daily or placebo.
Cisapride 20 mg four times daily was started after 7 days of fluconazole or
placebo dosing. Following a single dose of fluconazole, there was a 101% increase
in the cisapride AUC and a 91% increase in the cisapride Cmax. Following multiple
doses of fluconazole, there was a 192% increase in the cisapride AUC and a 154%
increase in the cisapride Cmax. Fluconazole significantly increased the QTc
interval in subjects receiving cisapride 20 mg four times daily for 5 days.
(See CONTRAINDICATIONS and PRECAUTIONS.)
Midazolam: The effect of fluconazole on the pharmacokinetics
and pharmacodynamics of midazolam was examined in a randomized, cross-over study
in 12 volunteers. In the study, subjects ingested placebo or 400 mg fluconazole
on Day 1 followed by 200 mg daily from Day 2 to Day 6. In addition, a 7.5 mg
dose of midazolam was orally ingested on the first day, 0.05 mg/kg was administered
intravenously on the fourth day, and 7.5 mg orally on the sixth day. Fluconazole
reduced the clearance of IV midazolam by 51%. On the first day of dosing, fluconazole
increased the midazolam AUC and Cmax by 259% and 150%, respectively. On the
sixth day of dosing, fluconazole increased the midazolam AUC and Cmax by 259%
and 74%, respectively. The psychomotor effects of midazolam were significantly
increased after oral administration of midazolam but not significantly affected
following intravenous midazolam.
A second randomized, double-dummy, placebo-controlled, cross-over study in
three phases was performed to determine the effect of route of administration
of fluconazole on the interaction between fluconazole and midazolam. In each
phase the subjects were given oral fluconazole 400 mg and intravenous saline;
oral placebo and intravenous fluconazole 400 mg; and oral placebo and IV saline.
An oral dose of 7.5 mg of midazolam was ingested after fluconazole/placebo.
The AUC and Cmax of midazolam were significantly higher after oral than IV administration
of fluconazole. Oral fluconazole increased the midazolam AUC and Cmax by 272%
and 129%, respectively. IV fluconazole increased the midazolam AUC and Cmax
by 244% and 79%, respectively. Both oral and IV fluconazole increased the pharmacodynamic
effects of midazolam. (See PRECAUTIONS.)
Azithromycin: An open-label, randomized, three-way crossover
study in 18 healthy subjects assessed the effect of a single 800 mg oral dose
of fluconazole on the pharmacokinetics of a single 1200 mg oral dose of azithromycin
as well as the effects of azithromycin on the pharmacokinetics of fluconazole.
There was no significant pharmacokinetic interaction between fluconazole and
azithromycin.
Microbiology
Mechanism of Action
Fluconazole is a highly selective inhibitor of fungal cytochrome P-450 dependent enzyme lanosterol 14-α-demethylase. This enzyme functions to convert lanosterol to ergosterol. The subsequent loss of normal sterols correlates with the accumulation of 14-α-methyl sterols in fungi and may be responsible for the fungistatic activity of fluconazole. Mammalian cell demethylation is much less sensitive to fluconazole inhibition.
Activity In Vitro and In Clinical Infections
Fluconazole has been shown to be active against most strains of the following
microorganisms both in vitro and in clinical infections.
Candida albicans
Candida glabrata (Many strains are intermediately susceptible)*
Candida parapsilosis
Candida tropicalis
Cryptococcus neoformans
* In a majority of the studies, fluconazole MIC90 values
against C. glabrata were above the susceptible breakpoint ( ≥ 16µg/ml). Resistance
in Candida glabrata usually includes upregulation of CDR genes resulting in
resistance to multiple azoles. For an isolate where the MIC is categorized as
intermediate (16 to 32 µg/ml, see Table 1), the highest dose is recommended
(see DOSAGE AND ADMINISTRATION). For resistant isolates alternative
therapy is recommended.
The following in vitro data are available, but their clinical significance
is unknown.
Fluconazole exhibits in vitro minimum inhibitory concentrations (MIC
values) of 8 µg/mL or less against most ( ≥ 90%) strains of the following microorganisms,
however, the safety and effectiveness of fluconazole in treating clinical infections
due to these microorganisms have not been established in adequate and well controlled
trials.
Candida dubliniensis
Candida guilliermondii
Candida kefyr
Candida lusitaniae
Candida krusei should be considered to be resistant to fluconazole. Resistance
in C. krusei appears to be mediated by reduced sensitivity of the target
enzyme to inhibition by the agent.
There have been reports of cases of superinfection with Candida species
other than C. albicans, which are often inherently not susceptible to
DIFLUCAN (e.g., Candida krusei). Such cases may require alternative antifungal
therapy.
Susceptibility Testing Methods
Cryptococcus neoformans and filamentous fungi
No interpretive criteria have been established for Cryptococcus neoformans and filamentous fungi.
Candida species
Broth Dilution Techniques:Quantitative methods are used to determine
antifungal minimum inhibitory concentrations (MICs). These MICs provide estimates
of the susceptibility of Candida spp. to antifungal agents. MICs should
be determined using a standardized procedure. Standardized procedures are based
on a dilution method (broth)1 with standardized inoculum concentrations
of fluconazole powder. The MIC values should be interpreted according to the
criteria provided in Table 1.
Diffusion Techniques:Qualitative methods that require measurement
of zone diameters also provide reproducible estimates of the susceptibility
of Candida spp. to an antifungal agent. One such standardized procedure2
requires the use of standardized inoculum concentrations. This procedure uses
paper disks impregnated with 25 µg of fluconazole to test the susceptibility
of yeasts to fluconazole. Disk diffusion interpretive criteria are also provided
in Table 1.
Table 1: Susceptibility Interpretive Criteria for Fluconazole
| |
Broth Dilution at 48 hours
(MC in µg/mL) |
Disk Diffusion at 24 hours
(Zone Diameters in mm) |
| Antifungal agent |
Susceptible
(S) |
Intermediate
(I)** |
Resistant
(R) |
Susceptible
(S) |
Intermediate
(I)** |
Resistant
(R) |
| Fluconazole* |
≤ 8.0 |
16-32 |
≥ 64 |
≥ 19 |
15-18 |
≤ 14 |
* Isolates of C. krusei are assumed to be intrinsically
resistant to fluconazole and their MICs and/or zone diameters should not
be interpreted using this scale.
** The intermediate category is sometimes called Susceptible-Dose Dependent
(SDD) and both categories are equivalent for fluconazole. |
The susceptible category implies that isolates are inhibited by the usually achievable concentrations of antifungal agent tested when the recommended dosage is used. The intermediate category implies that an infection due to the isolate may be appropriately treated in body sites where the drugs are physiologically concentrated or when a high dosage of drug is used. The resistant category implies that isolates are not inhibited by the usually achievable concentrations of the agent with normal dosage schedules and clinical efficacy of the agent against the isolate has not been reliably shown in treatment studies.
Quality Control
Standardized susceptibility test procedures require the use of quality control organisms to control the technical aspects of the test procedures. Standardized fluconazole powder and 25 µg disks should provide the following range of values noted in Table 2. NOTE: Quality control microorganisms are specific strains of organisms with intrinsic biological properties relating to resistance mechanisms and their genetic expression within fungi; the specific strains used for microbiological control are not clinically significant.
Table 2: Acceptable Quality Control Ranges for Fluconazole
to be Used in Validation of Susceptibility Test Results
| QC Strain |
Macrodilution
(MIC in µg/mL) @ 48 hours |
Microdilution
(MIC in µg/mL) @ 48 hours |
Disk Diffusion
(Zone Diameter in mm)@ 24 hours |
| Candida parapsilosis ATCC 22019 |
2.0-8.0 |
1.0-4.0 |
22-33 |
| Candida krusei ATCC 6258 |
16-64 |
16-128 |
---* |
| Candida albicans ATCC 90028 |
---* |
---* |
28-39 |
| Candida tropicalis ATCC 750 |
---* |
---* |
26-37 |
| ---* Quality control ranges have not been established
for this strain/antifungal agent combination due to their extensive interlaboratory
variation during initial quality control studies. |
Activity In Vivo
Fungistatic activity has also been demonstrated in normal and immunocompromised
animal models for systemic and intracranial fungal infections due to Cryptococcus
neoformans and for systemic infections due to Candida albicans.
In common with other azole antifungal agents, most fungi show a higher apparent
sensitivity to fluconazole in vivo than in vitro. Fluconazole
administered orally and/or intravenously was active in a variety of animal models
of fungal infection using standard laboratory strains of fungi. Activity has
been demonstrated against fungal infections caused by Aspergillus flavus
and Aspergillus fumigatus in normal mice. Fluconazole has also been shown
to be active in animal models of endemic mycoses, including one model of Blastomyces
dermatitidispulmonary infections in normal mice; one model of Coccidioides
immitis intracranial infections in normal mice; and several models of Histoplasma
capsulatum pulmonary infection in normal and immunosuppressed mice. The
clinical significance of results obtained in these studies is unknown.
Oral fluconazole has been shown to be active in an animal model of vaginal candidiasis.
Concurrent administration of fluconazole and amphotericin B in infected normal
and immunosuppressed mice showed the following results: a small additive antifungal
effect in systemic infection with C. albicans, no interaction in intracranial
infection with Cryptococcus neoformans, and antagonism of the two drugs
in systemic infection with A. fumigatus. The clinical significance of
results obtained in these studies is unknown.
Drug Resistance
Fluconazole resistance may arise from a modification in the quality or quantity of the target enzyme (lanosterol 14-α-demethylase), reduced access to the drug target, or some combination of these mechanisms.
Point mutations in the gene (ERG11) encoding for the target enzyme lead
to an altered target with decreased affinity for azoles. Overexpression of ERG11
results in the production of high concentrations of the target enzyme, creating
the need for higher intracellular drug concentrations to inhibit all of the
enzyme molecules in the cell.
The second major mechanism of drug resistance involves active efflux of fluconazole
out of the cell through the activation of two types of multidrug efflux transporters;
the major facilitators (encoded by MDR genes) and those of the ATP-binding
cassette superfamily (encoded by CDR genes). Upregulation of the MDR
gene leads to fluconazole resistance, whereas, upregulation of CDR genes
may lead to resistance to multiple azoles.
Resistance in Candida glabrata usually includes upregulation of CDR
genes resulting in resistance to multiple azoles. For an isolate where the MIC
is categorized as Intermediate (16 to 32 µg/mL), the highest fluconazole dose
is recommended.
Candida krusei should be considered to be resistant to fluconazole.
Resistance in C. krusei appears to be mediated by reduced sensitivity
of the target enzyme to inhibition by the agent.
There have been reports of cases of superinfection with Candida species
other than C. albicans, which are often inherently not susceptible to
DIFLUCAN (e.g., Candida krusei). Such cases may require alternative antifungal
therapy.
Clinical Studies
Cryptococcal meningitis: In a multicenter study comparing DIFLUCAN
(200 mg/day) to amphotericin B (0.3 mg/kg/day) for treatment of cryptococcal
meningitis in patients with AIDS, a multivariate analysis revealed three pretreatment
factors that predicted death during the course of therapy: abnormal mental status,
cerebrospinal fluid cryptococcal antigen titer greater than 1:1024, and cerebrospinal
fluid white blood cell count of less than 20 cells/mm3. Mortality
among high risk patients was 33% and 40% for amphotericin B and DIFLUCAN patients,
respectively (p=0.58), with overall deaths 14% (9 of 63 subjects) and 18% (24
of 131 subjects) for the 2 arms of the study (p=0.48). Optimal doses and regimens
for patients with acute cryptococcal meningitis and at high risk for treatment
failure remain to be determined. (Saag, et al. N Engl J Med 1992; 326:83-9.)
Vaginal candidiasis: Two adequate and well-controlled studies
were conducted in the U.S. using the 150 mg tablet. In both, the results of
the fluconazole regimen were comparable to the control regimen (clotrimazole
or miconazole intravaginally for 7 days) both clinically and statistically at
the one month post-treatment evaluation.
The therapeutic cure rate, defined as a complete resolution of signs and symptoms
of vaginal candidiasis (clinical cure), along with a negative KOH examination
and negative culture for Candida (microbiologic eradication), was 55%
in both the fluconazole group and the vaginal products group.
| |
Fluconazole PO 150 mg tablet |
Vaginal Product qhs x 7 days |
| Enrolled |
448 |
422 |
| Evaluable at Late Follow-up |
347 (77%) |
327 (77%) |
| Clinical cure |
239/347 (69%) |
235/327 (72%) |
| Mycologic erad. |
213/347 (61%) |
196/327 (60%) |
| Therapeutic cure |
190/347 (55%) |
179/327 (55%) |
Approximately three-fourths of the enrolled patients had acute vaginitis ( < 4 episodes/12 months) and achieved 80% clinical cure, 67% mycologic eradication and 59% therapeutic cure when treated with a 150 mg DIFLUCAN tablet administered orally. These rates were comparable to control products. The remaining one-fourth of enrolled patients had recurrent vaginitis ( ≥ 4 episodes/12 months) and achieved 57% clinical cure, 47% mycologic eradication and 40% therapeutic cure. The numbers are too small to make meaningful clinical or statistical comparisons with vaginal products in the treatment of patients with recurrent vaginitis.
Substantially more gastrointestinal events were reported in the fluconazole group compared to the vaginal product group. Most of the events were mild to moderate. Because fluconazole was given as a single dose, no discontinuations occurred.
| Parameter |
Fluconazole PO |
Vaginal Products |
| Evaluable patients |
448 |
422 |
| With any adverse event |
141 (31%) |
112 (27%) |
| Nervous System |
90 (20%) |
69 (16%) |
| Gastrointestinal |
73 (16%) |
18 ( 4%) |
| With drug-related event |
117 (26%) |
67 (16%) |
| Nervous System |
61 (14%) |
29 ( 7%) |
| Headache |
58 (13%) |
28 ( 7%) |
| Gastrointestinal |
68 (15%) |
13 ( 3%) |
| Abdominal pain |
25 ( 6%) |
7 ( 2%) |
| Nausea |
30 ( 7%) |
3 ( 1%) |
| Diarrhea |
12 ( 3%) |
2 ( < 1%) |
| Application site event |
0 ( 0%) |
19 ( 5%) |
| Taste Perversion |
6 ( 1%) |
0 ( 0%) |
Pediatric Studies
Oropharyngeal candidiasis: An open-label, comparative study of
the efficacy and safety of DIFLUCAN (2-3 mg/kg/day) and oral nystatin (400,000
I.U. 4 times daily) in immunocompromised children with oropharyngeal candidiasis
was conducted. Clinical and mycological response rates were higher in the children
treated with fluconazole.
Clinical cure at the end of treatment was reported for 86% of fluconazole treated patients compared to 46% of nystatin treated patients. Mycologically, 76% of fluconazole treated patients had the infecting organism eradicated compared to 11% for nystatin treated patients.
| |
Fluconazole |
Nystatin |
| Enrolled |
96 |
90 |
| Clinical Cure |
76/88 (86%) |
36/78 (46%) |
| Mycological eradication* |
55/72 (76%) |
6/54 (11%) |
|
* Subjects without follow-up cultures for any reason were considered
nonevaluable for mycological response.
|
The proportion of patients with clinical relapse 2 weeks after the end of treatment
was 14% for subjects receiving DIFLUCAN and 16% for subjects receiving nystatin.
At 4 weeks after the end of treatment the percentages of patients with clinical
relapse were 22% for DIFLUCAN and 23% for nystatin.
REFERENCES
1. Clinical and Laboratory Standards Institute. Reference Method
for Broth Dilution Antifungal Susceptibility Testing of Yeasts; Approved Standard-Second
Edition. CLSI Document M27-A2, 2002 Volume 22, No 15, CLSI, Wayne, PA, August
2002.
2. Clinical and Laboratory Standards Institute. Methods for
Antifungal Disk Diffusion Susceptibllity Testing of Yeasts; Approved Guideline.
CLSI Document M44-A, 2004 Volume 24, No. 15 CLSI, Wayne, PA, May 2004.
3. Pfaller, M. A., Messer,S. A., Boyken, L., Rice, C, Tendolkar,
S., Hollis, R. J., and Diekema1, D. J. Use of Fluconazole as a Surrogate Marker
To Predict Susceptibility and Resistance to Voriconazole among 13,338 Clinical
Isolates of Candida spp. Tested by Clinical and Laboratory Standard Institute-Recommended
Broth Microdilution Methods. 2007. Journal of Clinical Microbiology. 45:70-75.
Last updated on RxList: 8/14/2009