Comparative Pharmacokinetic Evaluation of Oral Anastrozole Suspension and Transdermal Nano-Spanlastics Patches in Albino Rabbits

Background: Anastrozole is a cornerstone in the treatment of estrogen receptor-positive breast cancer in postmenopausal women. Oral administration presents several challenges that can impact therapeutic efficacy and patient adherence. The adverse effects can potentially compromise treatment outcomes. Objective: To compare the bioavailability of Anastrozole as a transdermal ANS-nano-spanlastics (SPLs) patch with oral ANS-suspension. Methods: This study involved 12 female albino rabbits, weighing 2 kg, which were randomly divided into two groups of six animals each. Group I received a dose of 0.104 mg of pure anastrozole suspension orally, while Group II was administered anastrozole as transdermal nano-Spanlastic patches. Plasma anastrozole concentrations were quantified using reverse-phase high-performance liquid chromatography (RP-HPLC). Results: The results demonstrated significant differences between the oral and transdermal delivery of Anastrozole. For the oral suspension, the maximum plasma concentration was 38 ng/mL, achieved at 1.5 hours, with an AUC of 368 ng · h/mL. The nano-spanlastic patch produced a lower Cmax (24.2 ng/ml) at a delayed Tmax (24 hours) and a significantly greater AUC (10714.58 ng·h/ml). The relative bioavailability of the transdermal formulation was 29 times higher than that of the oral route after 120 hr. Conclusions: The nanospanlastic transdermal patch offers a more efficient and sustained method of anastrozole delivery compared to conventional oral suspension.