Ethosomal gel for rectal transmucosal delivery of domperidone: design of experiment, in vitro, and in vivo evaluation

Figures & data

Table 1. Full factorial design (2¹, 5¹) used for optimization formulations showing independent, dependent variables (responses) and desired outcomes.

Independent variables	Levels
	Low	High
Lecithin concentration	2%	3%
Additives	None	Tween 80, Labrafac^®, oleic acid, span 60
Dependent variables	Unit	Goal
Mean vesicular size	nm	Minimize
PDI	–	Minimize
Zeta potential	mV	Maximize
EE	Percent	Maximize
Q6h	Percent	Maximize

PDI: polydispersity index; EE: entrapment efficiency; Q6h: % cumulative drug release for 6 h.

Table 2. Composition of DOM-loaded ethosomal suspensions.

Formulation code	Total lipid content (lecithin/oils) (%)	Additives
		Tween 80 (% w/v)	Span 60 (% w/v)	Labrafac^® (% w/w of total lipid)	Oleic acid (%w/w of total lipid)
F1	2	–	–	–	–
F2	2	–	–	–	10 %
F3	2	–	–	10%	–
F4	2	2%		–	–
F5	2		2%
F6	3	–	–	–	–
F7	3	–	–	–	10%
F8	3	–	–	10%	–
F9	3	2%	–	–	–
F10	3	–	2%	–	–

Each formula also contains 30% ethanol, 10 mg DOM, and 1 mL PG.

Table 3. Composition of prepared gels loaded DOM-ethosomal suspension.

Formulations code	Polymer	Polymer weight (g) (w/w) (%)	Gel load	Distilled water (g)
F11	Carbopol 934	0.5	Ethosomal suspension equivalent to 30 mg DOM	Up to 50
F12		1		Up to 50
F13		0.5	30 mg free DOM	Up to 50
F14		1		Up to 50

Table 4. Vesicular size, PDI, zeta potential (ZP), EE%, and % drug released after 6 h (Q6h) of DOM-loaded ethosomal suspension (mean ± SD, n = 3).

Formulations	PS	PDI	ZP	%EE	Q6h	Desirability
F1	177.3 ± 2.96	0.39 ± 0.01	–55.3 ± 0.26	61.19 ± 4.57	40.70 ± 3.22	0.564
F2	144.3 ± 3.09	0.38 ± 0.01	–58.9 ± 0.31	67.11 ± 5.94	50.80 ± 5.46	0.667
F3	112 ± 3.3	0.32 ± 0.01	–59 ± 0.28	70.02 ± 5.52	76.30 ± 2.45	0.811
F4	75.5 ± 3.63	0.42 ± 0.01	–51.4 ± 0.35	62.20 ± 5.89	63.40 ± 7.33	0.568
F5	245 ± 5.7	0.49 ± 0.02	–39.4 ± 0.32	75.17 ± 6.66	37.30 ± 5.66	0.491
F6	212 ± 7.92	0.45 ± 0.02	–56.8 ± 0.28	75.12 ± 2.17	37.30 ± 4.32	0.500
F7	177 ± 4.35	0.4 ± 0.01	–56.8 ± 0.37	73.21 ± 8.43	41.01 ± 6.21	0.521
F8	135 ± 2.18	0.36 ± 0.01	–43 ± 0.45	77.14 ± 5.46	50.80 ± 8.23	0.537
F9	95 ± 2.23	0.27 ± 0.01	–51.7 ± 0.21	72.13 ± 7.45	45.70 ± 4.54	0.600
F10	344 ± 2.11	0.51 ± 0.01	–45.2 ± 0.23	80.14 ± 2.33	35.12 ± 6.44	0.452

PS: particle size; PDI: polydispersity index; ZP: zeta potential; Q6hrs: % cumulative drug release for 6 h.

Figure 1. In vitro release profiles of DOM solution and different DOM-loaded ethosomes formulations in phosphate buffer saline (pH 6.8) at 37 °C ± 0.5 °C.

Figure 2. Response bar plots for the effect of lecithin concentration (%) (X1) and additives (X2) on (A) PS, (B) ZP, (C) %EE, and (D) Q6h on DOM-loaded ethosomes.

Table 5. Output data of the (2¹, 5¹) full factorial analysis of the formulas, predicted and actual values for the optimum formulation (F3).

Responses	PS	PDI	ZP	%EE	Q6h
Adequate precision	55.275	43.634	38.194	15.147	65.29
Adjusted R^2	0.9934	0.9912	0.9899	0.8812	0.9959
Predicted R^2	0.9837	0.9782	0.977	0.7969	0.9898
Significant factors	X1, X2	X1, X2	X1, X2	X1, X2	X1, X2

Figure 3. (A) Desirability 3D surface. (B) Desirability plot of the optimized formulation F3.

Figure 4. Particle size distribution of optimum formulation F3.

Table 6. The actual results of optimum formulation against the suggested one.

Item	Vesicular size (nm)	PDI	Zeta potential (mV)	%EE	Q6h
Actual F3 results	112	0.32	–59	70.02	76.3
Predicted F3 results	108.55	0.32	–58.6	69.885	75.4
Significance	Statistically insignificant p < 0.05

PDI: polydispersity index; EE: entrapment efficiency.

Figure 5. TEM image of the optimized DOM-loaded ethosomes (F3).

Figure 6. DSC thermograms of pure DOM, lecithin, and optimized DOM-loaded ethosomes (F3).

Figure 7. FTIR of pure DOM, lecithin, and optimum formula F3.

Table 7. Effect of storage on properties of selected formulation (F3).

Parameter	Fresh prepared F3	F3 after 3 months of storage at 25 °C	F3 after 3 months of storage at 4 °C
PS (nm)	112 ± 3.3	120 ± 5.4	113.5 ± 3.2
PDI	0.32 ± 0.01	0.4 ± 0.11	0.325 ± 0.04
ZP	–59 ± 0.28	–55 ± 0.79	–59 ± 0.56
%EE	70.02 ± 5.5	65.9 ± 2.30	69.88 ± 1.13
Q6h	76.30 ± 2.45	72.99 ± 4.5	76.45 ± 3.35

EE%: entrapment efficiency percentage; PDI: polydispersity index; PS: particle size; Q6h: amount of drug released after 6 h; ZP: zeta potential.

Data are presented as mean ± SD (n = 3).

Figure 8. Ex vivo permeation profiles of DOM from prepared ethosomal suspension (F3) compared to pure drug.

Figure 9. Rheological behavior of (a) (F11) ethosomal rectal gel (0.5% Carbopol), (b) (F12) ethosomal rectal gel (1% Carbopol), (c) (F13) free drug rectal gel 0.5% Carbopol, and (d) (F14) free drug rectal gel (1% Carbopol).

Figure 10. Mean DOM plasma concentration-time curves in rats after administration of a single dose (3.1 mg/kg) of DOM-loaded ethosomal gel (F11) and pure DOM gel (F13).

Table 8. Mean pharmacokinetics parameters of DOM following single rectal administration for DOM-loaded ethosomal gel (F11) and pure DOM gel (F13).

Pharmacokinetic parameters	DOM-loaded ethosomal gel (F11)	Pure DOM gel (F13)
Cmax (ng/mL)	50.2 ± 3.65	19.6 ± 4.65
Tmax (h)	2	4
AUC0–48 (ng.h/mL)	839.95 ± 21.2	335.25 ± 28.55
%Relative bioavailability	250%	100%
Elimination rate constant (ke)	0.0314 h^−1	0.061 h^−1
Mean residence time	33 h	16 h
Half-life (t1/2)	22 h	11.3 h

Data are represented as mean ± SD (n = 3).

Data availability statement

All data and materials are available.