2.9. In Vivo Pharmacokinetic Studies

In vivo studies were conducted after obtaining approval from the Animal Ethical Committee of the Institution of the Clinical Laboratory Center, Beni Suef, Egypt (Approval no. 22/9-09-22). PK solver software was used to analyze the pharmacokinetic (PK) performance of NC after oral and transdermal delivery. Wistar albino adult male rats weighing approximately 180–250 g were used. The following is a breakdown of a single dose trial of four groups of six animals each. Simvastatin suspension (10 mg/kg) was used in Test Group I. XG-SIM-NC (10 mg/kg) and XG-SIM-NC (10 mg/kg) were used in Test Groups II and III.

Prior to receiving medication formulations, animals fasted for 24 h while still having unrestricted access to water. The abdominal hair was cut the day before the experiment by using a depilatory product for 10 min and then washing it with distilled water. The animals were sedated with ketamine (10 m/kg, i.p.) and placed in a supine position on the day of the experiment. With the aid of an oral feeding needle, all test samples were given orally (10 mg/kg). A retro-orbital puncture was used to collect blood samples totaling roughly 0.5 mL at intervals of 0.5, 2, 4, 8, 12, 24, and 48 h following oral administration. Capillary tubes were used to transfer the samples from a retro-orbital puncture into a glass tube that had been heparinized and included the anticoagulant ammonium oxalate (1% solution). The plasma was promptly separated by microcentrifugation at 5000 rpm and then kept at 20 °C pending HPLC analysis [43,44].

After centrifuging 1.5 mL of animal blood at 5000 rpm for 5 min, 0.75 mL of plasma was recovered. Then, 0.5% trichloroacetic acid was added to this sample. Medicine was separated from plasma at 4000 rpm for 15 min at 4 °C [45,46]. The simvastatin in the plasma sample was measured using the supernatant solution put into HPLC. HPLC measured plasma simvastatin levels. Flow rate: 1.0 mL/min; injection volume: 5 uL; column: reversed-phase C18 column (250 mm 4.6 mm i.d., 5 m particle size).

The PK solver application shows HPLC data on time versus plasma drug concentration. Peak plasma concentration (Cmax), time required to attain Cmax (tmax), area under the curve (AUC0-t), and (AUC0-) were directly read from the individual plasma drug concentration versus time profile. Biological half-life (t1/2) and mean residence time (MRT) were also calculated using PK solver software [47].