Albendazole (ABZ), while useful in medical treatments, can have toxic side effects when used improperly. To mitigate this, Comenius University Bratislava researchers led efforts to monitor ABZ and its derivatives using liquid chromatography–tandem mass spectrometry (LC–MS/MS). Their findings were published in the Journal of Chromatography B (1).
Albendazole (ABZ/methyl-[(5-propylthio)-1H-benzimidazol-2-yl] carbamate) is a benzimidazole derivative that is used for a broad variety of anthelmintic activity, the effectiveness of compounds in expelling or killing parasitic worms (2). It is an approved medication for treating various parasitic worm infections, including neurocysticercosis, ascariasis, and human alveolar echinococcosis (AE). AE is a parasitic tapeworm infection that can be found in foxes, coyotes, and dogs (3). It is caused by tumor-like or cyst-like tapeworm larvae growing in the body, and while cases in people are rare, left untreated, AE can be fatal. After diagnosis, treatment typically involves radical surgical removal of cysts followed by prophylaxis using ABZ. For patients that cannot have surgery, treatment consists of continuous and long-term ABZ administration.
ABZ absorption is relatively poor and is affected by diet. ABZ typically undergoes extensive and rapid first-pass metabolism, mediated by cytochrome isoenzymes and flavin-containing monooxygenase, to form albendazole sulfoxide (ASOX) and albendazole sulfone (ASON). ASOX is an active metabolite responsible for the efficacy of the ABZ treatment; however, it contributes to toxicity and side effects, such as hepatotoxicity, myelosuppression or hair loss. Low ASOX concentrations may cause inadequate response or even to failure of the therapy. Therefore, ABZ therapy is a candidate for routine therapeutic drug monitoring (TDM).
In this study, a liquid chromatography–tandem mass spectrometry (LC–MS/MS) method was created for the simultaneous quantification of ABZ, ASOX, and ASON in human plasma. The method was used to monitor the plasma levels of albendazole (0.25–200 ng/mL), albendazole sulfoxide (5–3500 ng/mL), and albendazole sulfone (0.5–500 ng/mL) with a coefficient of variation below 7%. A one-step extraction procedure was applied, with extracts being analyzed by gradient elution followed by detection on a mass spectrometer in multiple reaction monitoring mode. The method was said to offer numerous advantages, including a low sample volume (50 μL), a short run time (4 min), and sufficient linearity to quantify both low and high concentrations of all analytes.
The method was successfully validated according to guideline M10 of the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use (ICH). This guideline is said to discuss bioanalytical method validation, covering selectivity, linearity of the calibration curve, lower limit of quantification (LLOQ), accuracy, precision, dilution integrity, carry-over effect, matrix effects, extraction recovery, and stability.
The fully developed and validated method was used to determine ABZ, ASOX, and ASON in the plasma samples of ten patients. Samples were collected four hours after 400 mg of ABZ suspension was administered, regardless of body weight. Measured plasma levels varied from 332–2897 (median 911.5) ng/mL for ASOX, 19.2–202.6 (median 58.7) ng/mL for ASON, and 2.2–167.5 (median 25.2) ng/mL for ABZ. Five out of ten patients had ASOX levels outside the recommended therapeutic range (higher than the recommended upper limit of 843 ng/mL). One patient displayed abnormal pharmacokinetics and significantly elevated levels of all analytes, with the researchers discovering that ASOX levels in the patient were 3.5 times higher than the upper recommended limit. This patient experienced hair loss, likely because of high ASOX levels.
ABZ was deemed a suitable candidate for routine therapeutic drug monitoring. The recommended therapeutic regimen of ABZ is 10–15 mg/kg daily divided into two doses, usually 400 mg twice daily, regardless of body weight. Considering the abovementioned regime, the plasma level of ASOX should be within 1–3 μmol/L four hours after the dose (peak levels of ASOX). By following this practice, TDM could be a valuable tool for clinicians treating patients with ABZ.
(1) Žideková, N.; Kertys, M.; Mokrý, J.; et al. A High-Throughput LC-MS/MS Method for Simultaneous Analysis of Albendazole, Albendazole Sulfoxide and Albendazole Sulfone in Human Plasma. J. Chromatogr. B 2025, 1263, 124741. DOI:
(2) Anthelmintic Activity. ScienceDirect 2020.
(3) About Alveolar Echinococcosis (AE). CDC 2024.
