Because anidulafungin is generally well tolerated and appears to have limited interaction with other drugs, it is a potential important agent in the treatment of invasive fungal infections. Although anidulafungin is approved for the treatment of invasive candidiasis in adult non-neutropenic patients, dosing guidelines for anidulafungin in (morbidly) obese patients are not available. Subsequently, the pharmacokinetic profile of anidulafungin (as well as other echinocandins) in this specific patient population is still largely unknown. During endoscopic gastric bypass surgery, patients are more prone to various kinds of infection, justifying the prophylactic use of anidulafungin in this specific cohort of patients.

To build a valid pharmacokinetic model, obese patients with a BMI ≥ 40 undergoing endoscopic gastric bypass surgery will receive a single dose of 100 mg anidulafungin (besides standard anti-bacterial prophylaxis) and a PK-curve will be drawn. These PK-values can then be compared to the pharmacokinetics in a normal-weight group.

All obese patients with a BMI ≥ 40 kg/m2 undergoing endoscopic gastric bypass surgery who receive a prophylactic single dose of 100 mg anidulafungin will be included in the analysis. A PK curve will be determined after administration of anidulafungin at t=0.5, 1, end of infusion, 2, 4, 6, 8, 10, 12, 24, and 48 and (if feasible) 72 hours post infusion (n=12 samples). Blood samples (4 mL) on PK days will be taken to obtain at least 2.0 mL of plasma.

Inclusion Criteria:

1. Patient has a BMI ≥40 kg/m2 and is undergoing endoscopic gastric bypass surgery.
2. Subject is at least 18 years of age on the day of screening.
3. If subject is female: neither pregnant, nor able to become pregnant and is not nursing an infant.
4. Subject or legal representatives are able and willing to sign the Informed Consent before screening evaluations.

Exclusion Criteria:

1. Documented history of sensitivity to medicinal products or excipients similar to those found in the echinocandin preparation.
2. History of, or current abuse of drugs, alcohol or solvents.
3. Inability to understand the nature of the trial and the procedures required.