Intranasal delivery of Clozapine using nanoemulsion-based in-situ gels: An approach for bioavailability enhancement

Abstract

Limited solubility and hepatic first-pass metabolism are the main causes of low bioavailability of anti-schizophrenic drug, Clozapine (CZP). The objective of the study was to develop and validate nanoemulsion (NE) based in-situ gel of CZP for intranasal administration as an approach for bioavailability enhancement. Solubility of CZP was initially investigated in different oils, surfactants and co-surfactants, then pseudoternary phase diagrams were constructed to select the optimized ratio of oil, surfactant and co-surfactant. Clear and transparent NE formulations were characterized in terms of droplet size, viscosity, solubilization capacity, transmission electron microscopy, in-vitro drug release and compatibility studies. Selected NEs were incorporated into different in-situ gel bases using combination of two thermosensitive polymers; Pluronic® F-127 (PF127) and F-68 (PF68). NE-based gels (NG) were investigated for gelation temperature, viscosity, gel strength, spreadability and stability. Moreover, selected NGs were evaluated for ex-vivo permeation, mucoadhesive strength and nasal ciliotoxicity. Peppermint oil, tween 80 and transcutol P were chosen for NE preparation owing to their maximum CZP solubilization. Clear NE points extrapolated from tween 80:transcutol P (1:1) phase diagram and passed dispersibility and stability tests, demonstrated globule size of 67.99 to 354.96 nm and zeta potential of -12.4 to -3.11 mV with enhanced in-vitro CZP release (>90% in some formulations). After incorporation of the selected N3 and N9 formulations of oil:Smix of 1:7 and 2:7, respectively to a mixture of PF127 and PF68 (20:2% w/w), the resultant NG formulations exhibited optimum gelation temperature and viscosity with enhanced CZP permeation and retention through sheep nasal mucosa. Ciliotoxicity examinations of the optimum NGs displayed no inflammation or damage of the lining epithelium and the underlying cells of the nasal mucosa. In conclusion, NE-based gels may be a promising dosage form of CZP for schizophrenia treatment.

Keywords: Emulsification time; Ex-vivo permeation; Nasal ciliotoxicity; Pluronic® gel; Pseudoternary phase diagram; Transcutol P.

Fig. 1

Study of pseudoternary phase diagrams using different cosurfactants (A) transcutol P (B) PG (C) ethanol (D) plurol oleique CC 497 (E) lauroglycol 90.

Fig. 2

Study of pseudoternary phase diagrams using peppermint oil, tween 80 and transcutol P at different Smix ratios of (A) 1:0 (B) 1:1 (C) 1:2 (D) 1:3 (E) 2:1 (F) 3:1.

Fig. 3

TEM images of NE at different scales (A) 0.5 μm (B) 100 nm (C) 200 nm.

Fig. 4

In-vitro release of different CZP-loaded NE formulations (N1-N15) in comparison to pure drug suspension.

Fig. 5

In-vitro release of CZP-loaded NG3 formulations containing N9 and N3 compared to their corresponding NE formulations and control gel formulation.

Fig. 6

(A) DSC thermograms of (a) peppermint oil (b) tween 80 (c) transcutol P (d) blank NE.

(B) DSC thermograms of (a) pure CZP (b) blank NE (c) N3 (d) N9 (e) NG3 containing N3 (f) NG3 containing N9

Fig. 7

FTIR spectrums of (a) pure CZP (b) peppermint oil (c) tween 80 (d) transcutol P (e) blank NE (f) N3 (g) N9 (h) NG3 containing N3 (i) NG3 containing N9.

Fig. 8

Ex-vivo permeation of NG3 containing either N9 or N3 in comparison to control gel formulation.

Fig. 9

Nasal cilotoxicity study of sheep nasal mucosa treated with (a) saline (b) isopropyl alcohol (c) NG3 containing N3 (d) NG3 containing N9.