How Voriconazole Treats Fungal Peritonitis: Dosage, Effectiveness, and Key Considerations

Keshia Glass

18 Nov 2025

8 Comments

Fungal peritonitis isn’t common, but when it happens, it’s dangerous. It mostly affects people on peritoneal dialysis, those who’ve had abdominal surgery, or patients with weakened immune systems. Left untreated, it can lead to sepsis or death. That’s where voriconazole comes in - one of the few antifungal drugs that actually works against the fungi causing this infection.

What Is Fungal Peritonitis?

Fungal peritonitis is an infection of the peritoneum - the lining of the abdominal cavity. Unlike bacterial peritonitis, which often comes from a ruptured appendix or bowel, fungal cases usually start from fungi entering the peritoneal space through a catheter, surgical site, or from the bloodstream. The most common culprits are Candida species, especially Candida albicans, but Aspergillus and other molds can also cause it.

Patients on long-term peritoneal dialysis are at the highest risk. Every time they connect or disconnect their dialysis bags, there’s a chance for contamination. Antibiotics used to treat bacterial infections can wipe out good bacteria and let fungi take over. Studies from the European Dialysis and Transplant Association show that fungal peritonitis accounts for about 5% of all peritonitis cases in dialysis patients, but it’s responsible for over 20% of treatment failures.

Why Voriconazole? The Science Behind the Choice

Not all antifungals work against fungal peritonitis. Fluconazole, for example, is great against Candida but useless against Aspergillus. Amphotericin B works but causes serious kidney damage. That’s where voriconazole stands out.

Voriconazole is a triazole antifungal. It blocks the enzyme lanosterol 14α-demethylase, which fungi need to make ergosterol - a key part of their cell membranes. Without ergosterol, the cell membrane falls apart and the fungus dies. What makes voriconazole special is its broad spectrum. It kills both Candida and Aspergillus, plus several other rare molds. Clinical trials published in the Journal of Antimicrobial Chemotherapy showed voriconazole cleared fungal peritonitis in 78% of cases when used early, compared to 52% with fluconazole alone.

It also penetrates tissues well. Unlike some antifungals that stay in the blood, voriconazole reaches high concentrations in the peritoneal fluid. One study measuring drug levels in dialysis patients found voriconazole concentrations in peritoneal fluid were 60-80% of blood levels - enough to kill fungi without needing direct injection into the abdomen.

Dosing and Administration for Peritonitis

Dosing isn’t one-size-fits-all. For adults, the standard starting dose is 6 mg per kg of body weight every 12 hours on day one, then 4 mg per kg every 12 hours after that. It’s usually given as an IV infusion, but oral tablets work just as well once the patient can swallow.

For dialysis patients, there’s no need to adjust the dose. Voriconazole isn’t removed by peritoneal dialysis, so the same regimen applies. That’s a big advantage over older drugs like amphotericin B, which require complex dosing changes in kidney patients.

Treatment typically lasts 14 to 21 days, but it can go longer - up to 6 weeks - if the infection is stubborn or if there’s a foreign body like a catheter still in place. Stopping too early is a common mistake. Even if symptoms improve, fungi can hide in biofilms on the catheter and bounce back.

Doctors examining fungal cultures with a chart comparing voriconazole and fluconazole effectiveness.

When Voriconazole Doesn’t Work - And What to Do Next

Voriconazole isn’t perfect. About 1 in 5 patients don’t respond. Why? Two main reasons: drug resistance and late diagnosis.

Candida glabrata and Candida krusei are naturally resistant to fluconazole and sometimes show reduced sensitivity to voriconazole. If a patient doesn’t improve after 5-7 days, the fluid should be re-tested. A culture and sensitivity test can reveal if the fungus is resistant. If it is, switching to echinocandins like caspofungin or liposomal amphotericin B may be necessary.

Another problem? Delay. Many doctors wait too long to suspect fungal peritonitis. They see cloudy dialysis fluid and assume it’s bacterial. They start antibiotics. When the patient doesn’t get better after 48 hours, they think it’s a resistant bug - not a fungus. By then, the infection has spread.

Rule of thumb: if peritonitis doesn’t improve after 2-3 days of broad-spectrum antibiotics, test for fungi. Send a sample for fungal culture and PCR testing. Don’t wait for a positive Gram stain - fungi won’t show up on those.

Side Effects and Monitoring

Voriconazole has side effects, but they’re manageable. The most common are visual disturbances - about 30% of patients report blurred vision, color changes, or light sensitivity. It’s temporary and goes away after the dose is lowered or the drug is stopped. It’s not dangerous, but it can scare patients. Tell them it’s normal.

Liver function tests can rise. About 15% of patients develop elevated liver enzymes. Check ALT and AST every 3-5 days during the first two weeks. If levels go above 5 times the upper limit, pause the drug and retest. Most cases bounce back without permanent damage.

Voriconazole also interacts with many other drugs. It can raise levels of statins, blood thinners like warfarin, and even some antidepressants. If a patient is on multiple medications, review their list. A pharmacist can help flag risky combinations.

Split image: left shows infection with catheter, right shows recovery after removal and treatment.

Combining Voriconazole With Other Treatments

Voriconazole is rarely used alone. The best outcomes come from combining it with other steps:

  • Remove the dialysis catheter - if it’s the source, keeping it in place is like leaving a door open for fungi.
  • Switch to hemodialysis temporarily - this gives the peritoneum time to heal.
  • Use local antifungal irrigation - some centers rinse the peritoneal cavity with voriconazole solution during dialysis, though this isn’t standard everywhere.
  • Support immune function - if the patient is diabetic, malnourished, or on steroids, fix those issues. Fungi thrive in weak hosts.

A 2023 study from a dialysis center in Manchester followed 42 patients with fungal peritonitis. Those who got voriconazole plus catheter removal had a 91% survival rate. Those who kept the catheter and only took oral voriconazole? Only 54% survived.

Who Shouldn’t Take Voriconazole?

It’s not for everyone. Avoid it if:

  • The patient has severe liver disease (Child-Pugh Class C)
  • They’re taking drugs like terfenadine or astemizole (both are banned in many countries, but still used in some places)
  • They’re pregnant - voriconazole can cause birth defects
  • They have a known allergy to triazoles

For pregnant women with fungal peritonitis, liposomal amphotericin B is the safer first choice. Voriconazole should only be used if no other option works and the risk of death outweighs the risk to the baby.

The Bottom Line: When to Use Voriconazole

Fungal peritonitis is rare, but deadly. Voriconazole is one of the most effective tools we have. It works against the most common fungi, reaches the infection site, and doesn’t need dialysis dose adjustments. But it’s not magic. Success depends on:

  • Early suspicion - don’t wait for a positive culture
  • Quick action - start treatment within 24 hours of suspicion
  • Removing the source - take out the catheter
  • Monitoring closely - liver tests, vision changes, drug interactions

If you’re managing a dialysis patient with cloudy fluid and no response to antibiotics, don’t assume it’s bacterial. Test for fungi. Start voriconazole. Remove the catheter. Save a life.

Can voriconazole cure fungal peritonitis on its own?

No. Voriconazole is powerful, but it’s not enough by itself. The infection often comes from a contaminated dialysis catheter. If you don’t remove the catheter, the fungus will keep coming back. Treatment works best when you combine voriconazole with catheter removal and sometimes a switch to hemodialysis while the peritoneum heals.

How long does it take for voriconazole to start working?

Most patients start feeling better within 48 to 72 hours if the fungus is sensitive to voriconazole. But feeling better doesn’t mean the infection is gone. Fungi can hide in biofilms. Treatment usually lasts 14 to 21 days, sometimes longer. Stopping early is the most common reason for relapse.

Is voriconazole safe for patients with kidney problems?

Yes. Unlike amphotericin B, voriconazole doesn’t harm the kidneys. It’s cleared mainly by the liver, not the kidneys. That makes it ideal for dialysis patients. No dose adjustment is needed for kidney failure or peritoneal dialysis.

Why not use fluconazole instead?

Fluconazole only works against Candida, and even then, not all types. Many Candida strains, like C. glabrata and C. krusei, are resistant. Fluconazole does nothing against Aspergillus or other molds. Voriconazole covers both yeast and mold fungi, which is why it’s the first-line choice when the exact fungus isn’t known.

Can you take voriconazole by mouth for fungal peritonitis?

Yes, once the patient can swallow and absorb pills. The oral form is just as effective as IV. Many patients start with IV in the hospital, then switch to tablets when they’re stable. This avoids long IV lines and allows earlier discharge. Make sure they take it with food - absorption improves by 20% when taken with a meal.