How long does fluconazole stay in your system?
Fluconazole takes approximately 150 hours, or 6.25 days, to completely clear from the body.
This is why most fungal infections can be cleared with a single dose of fluconazole.
This is due to the drug’s properties related to its absorption, distribution, metabolism, and elimination.
The term used to explain these concepts is known as “Pharmacokinetics.”
To learn how and why, keep reading…
What is Fluconazole?
Fluconazole, often marketed under the brand name Diflucan, is an antifungal medication used to treat various fungal infections, including yeast infections in the mouth, throat, and genital areas.
Fluconazole is indicated for the treatment of the following conditions:
- Blastomycosis (not as effective as other, more powerful antifungals)
- Candidemia and Disseminated Candida Infections
- Oropharyngeal Candidiasis
- Esophageal Candidiasis
- Vulvovaginal Candidiasis
- Onychomycosis (nail fungus)
- Pityriasis (Tinea) Versicolor
- Prevention of Candidiasis in Transplant Recipients, Cancer Patients, or Other Patients at High Risk
Because it stays in the system for so long, it is conveniently dosed as a one-time, single pill for treating fungal infections.
Here is a short and to-the-point video covering fluconazole’s uses, contraindications, dosing, and side effects:
Pharmacokinetics of Fluconazole
To understand how long fluconazole remains in the system, it’s essential to grasp its pharmacokinetics – the movement of the drug through the body, covering absorption, distribution, metabolism, and excretion (A.D.M.E.).
- Absorption: Fluconazole is well-absorbed when taken orally, with plasma concentrations reaching their peak within 1 to 2 hours after taking the medication.
- Distribution: The drug distributes widely throughout the body, including the cerebrospinal fluid, saliva, and skin, which is beneficial for treating fungal infections in various body regions.
- Metabolism: Unlike many other drugs, fluconazole is not extensively metabolized in the liver (only about 11% of it is). Most of the drug remains unchanged in the body.
- Excretion: The primary mode of excretion for fluconazole is through the kidneys. About 80% of the administered dose can be found unchanged in the urine.
The video below clearly describes the concept of pharmacokinetics:
Half-life of Fluconazole
A crucial factor in determining how long a drug stays in your system is its half-life.
The half-life is the time it takes for the concentration of the drug in the bloodstream to be reduced by half.
For fluconazole, the half-life is relatively long, approximately 30 hours.
This means that 30 hours after taking the drug, half of its amount will still be present in your system.
Based on this half-life:
- After 30 hours (1 half-life): 50% of the drug remains.
- After 60 hours (2 half-lives): 25% remains.
- After 90 hours (3 half-lives): 12.5% remains.
- And so on…
Generally, a drug is considered to be effectively eliminated from the system after about 5 half-lives (This applies to any drug).
Thus, for fluconazole, it would take approximately 150 hours, or 6.25 days, for it to be almost entirely cleared from the body.
When does fluconazole peak in your system?
Fluconazole plasma concentrations peak about 2 hours after taking the medication.
This time frame is the same whether you take the oral dose or are given the intravenous dose.
Factors influencing how long fluconazole lasts in the body
Several factors can influence how long fluconazole remains in the system:
- Dosage: Higher doses might take longer to be eliminated from the body than lower doses.
- Kidney function: As fluconazole is primarily excreted via the kidneys, individuals with impaired kidney function might retain the drug longer.
- Age: Elderly individuals might process drugs more slowly than younger adults (read my articles on polypharmacy and the 2023 Beers Criteria).
- Frequency of use: Regular, repeated use can lead to drug accumulation, which may prolong the time it takes to eliminate the drug.
- Drug interactions: Some medications can interfere with how fluconazole is processed in the body.
Fluconazole interacts with 549 known medications!
This means that there is a high chance that one or more of your current medications may interact with fluconazole.
Some common medications fluconazole interacts with are:
- atorvastatin (Lipitor)
- amlodipine (blood pressure drug)
- losartan (blood pressure drug)
- prednisone or methylprednisolone
- alprazolam (Xanax – severe interaction)
- albuterol (moderate interaction)
- gabapentin, etc.
If you are prescribed fluconazole, asking your doctor or pharmacist about possible interactions is very important.
Additional cautions with fluconazole:
Liver toxicity: Can cause rare instances of liver toxicity
QT prolongation: Can cause rare cases of QT prolongation ( a heart rhythm problem)
People with kidney disease: Since the kidneys primarily remove fluconazole, any problems with them can cause you to retain the medication in the body and cause adverse effects.
Interaction with Alcohol: If you drink alcohol, use caution if you need to take fluconazole, as it can cause GI side effects.
In essence, while the half-life of fluconazole indicates that it remains in the system for an extended period relative to many other drugs (about 30 hours), most people will have effectively cleared the drug from their bodies within a week.
Always consult your healthcare provider regarding any concerns about medications, their side effects, or interactions.
Disclaimer: This article provides general information and should not be used as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or another qualified health provider with any questions related to your health or medications.