FORMULATION AND IN VITRO EVALUATION OF IN SITU GELLING LIQUID SUPPOSITORY OF PROMETHAZINE HCL

FORMULATION AND IN VITRO EVALUATION OF IN-SITU

GELLING LIQUID SUPPOSITORY OF PROMETHAZINE HCL

Iman S. Jaafar and Ameera A. Radhi*

Assistant Lecturer Department of Pharmaceutics, College of Pharmacy, University of

AlMustansiryah, Baghdad, Iraq.

ABSTRACT

The aim of this study was to formulate and in vitro evaluate a

thermogelling mucoadhesive liquid suppositories of promethazine

HCl(PMZ HCl) in order to improve the bioavailability, and decreases

the side effects as the absorbed drug avoids liver’s first pass

metabolism. Poloxamers P407 and P188 were used as thermo- gelling

agents and Hydroxypropyl methyl cellulose (HPMCK4M) as

mucoadhesive polymer. Thirteen formulas were prepared using cold

method and were evaluated for gelation temperature, gel strength, and

bioadhesive force and In-vitro release rate. Gelation temperature was

significantly increased with incorporation of 12.5 % w/v PMZ HCl

while decreased with addition of mucoadhesive polymer. The polymer

increased the gel strength and the mucoadhesive force of the prepared

solutions but significantly decreased the release rate. Among the

formulations examined, the P407/P188/HPMC (16/4/0.5 % w/v) and P407/ P188/ HPMC

(16/4/0.75 %w/v) that were used in formulas F9 and F10, respectively, were selected as the

bases of choice for PMZ HCl liquid suppository since they exhibited optimum physical

properties of gelation temperature, gel strength, high mucoadhesive force and a moderate

PMZ HCl in-vitro release. Therefore, these gels represent a promising alternative to

conventional suppositories and might be applicable for the development of in situ gelling and

mucoadhesive liquid suppository for humans as a more convenient and effective rectal

dosage form.

KEYWORDS: Thermogelling mucoadhesive, Poloxamers, Hydroxypropyl.

Volume 4, Issue 11, 273-286. Research Article ISSN 2277– 7105

*Correspondence for Author

Dr. Ameera A. Radhi

Assistant Lecturer

Department of

Pharmaceutics, College of

Pharmacy, University of

AlMustansiryah, Baghdad,

Iraq.

Article Received on 14 Sept. 2015,

INTRODUCTION

Promethazine Hydrochloride is an antiallergic, antihistaminic agent. It mediates its effect

through antagonizing the physiological and pathophysiological H1 mediated effect of

histamine.[1] It may also block the action of acetylcholine and this may explain the benefit in

reducing nausea and vomiting.[2]

It is used in treatment of allergic conditions, prevent or treat motion sickness, treat or avoid

nausea and vomiting in certain type of anesthesia and surgery and inducing sedation.[3]

Promethazine is well absorbed after oral or intramuscular dose with a peak plasma

concentration of 2 to 3 hours after a dose by these routes, although low systemic

bioavailability after oral doses due to high first pass metabolism in liver. It undergoes

extensive metabolism, predominantly to promethazine sulfoxide and also to N –desmethyl

promethazine.[4]

Nowadays one of the basic tasks of drug formulation is to develop an already existing dosage

form in a way which makes drug release the best possible under the given circumstances, that

is to enhance bioavailability in this way.[5]

The rectal route for drug administration was proven to be advantageous over other routes

because of the reduced side effects such as gastrointestinal irritation and the avoidance of

both disagreeable taste and first pass effect.[6]

A conventional suppository is a solid dosage form that melts or softens in the rectum at body

temperature. However solid suppository gives a feeling of alien, discomfort, and refusal to

the patients, possibly lowering patient compliance. Furthermore, if the solid suppositories

reach the end of the colon, the drugs delivered by the suppositories might undergo the

first-pass effect.[7]

In order to overcome these problems, a trail was made to establish a liquid rectal dosage form

which converts to a gel at body temperature which has a suitable gel strength in order not to

be leaked out from the anus after administration; and has a suitable bioadhesive force so as

not to reach the end of the colon.[8]

As a base of liquid suppository, Poloxamers as surfactants, are copolymers of poly

exhibit the phenomenon of reverse thermal gelation, remaining as solutions at low

temperature and gelling upon increasing the temperature.[10]

By modulating the gelation temperature of different poloxamer solutions, liquid bases for

rectal use can be formulated which form a gel in the rectum at body temperature with suitable

gel strength so as not to leak out from the anus after administration.[11] Furthermore, the

addition of mucoadhesives in these bases would reinforce the drug sustained action, and may

help in adhering the formed gel to the lower part of the rectum offering further protection

from the first pass effect, hence improving its bioavailability.[12]

The aim of this study was to formulate and in vitro evaluate a thermogelling mucoadhesive

system of promethazine HCl in order to improve the bioavailability, and decreases the side

effects as the absorbed drug avoids liver’s first pass metabolism. Physicochemical properties

such as gelation temperature, gel strength, and bioadhesive force of various formulations

composed of promethazine HCl, Poloxamers, and HPMCK4M as mucoadhesive polymer

were investigated.

MATERIALS

Promethazine HCl was purchased from Samara Drug Industry, Iraq. Poloxamer 407 and

Poloxamer 188 were purchased from M/s Provizer Pharma, Gujarat, India. Hydroxypropyl

methyl celleluse K4M was purchased from Alladine Industrial Co, Shanghai, China.

METHODS

Preparation of PMZ HCl liquid Suppositories

Poloxamer-based liquid suppositories were prepared by the cold method described by Choi et

al. (1998). 12.5 mg of PMZ HCl was dissolved in the calculated amount of distilled water at

room temperature. The mucoadhesive polymers were incorporated in PMZ HCl solutions.

P407/P188 was slowly added with continuous agitation using a magnetic bar. The mixtures

were left at 4°C in refrigerator until clear solutions were obtained.[13]

The medicated rectal solutions showing satisfactory gelation temperature (30-37oC) and

lower total poloxamer content were mixed with additional amounts of mucoadhesive

polymers namely: HPMC, in concentrations 0.5, 0.75, 1 and 2%, w/v.[11] Table 1 shows the

Table 1: Composition of Prepared Rectal Solutions

Formula No. P 407 % w/v P 188 % w/v HPMCK4M % w/v

F1 12

F2 14

F3 16

F4 18

F5 20

F6 16 4

F7 16 8

F8 16 12

F9 16 4 0.5

F10 16 4 0.75

F11 16 4 1

F12 16 4 2

F13 16 4 Without drug

Evaluation of In-situ Gelling Liquid Suppositories Measurement of Gelation Temperature

A 20-ml transparent vial containing a magnetic bar and 10 g of the liquid suppository was

placed in a low-temperature thermostat water bath. The liquid suppository was heated at a

constant stirring "50 (rpm)".When the magnetic bar stopped moving due to gelation, the

temperature was determined as the gelation temperature.[14] Only those liquid suppository

preparations that pass the gelation temperature test were subjected to the next tests.

Measurement of Gel Strength

Poloxamer solution (50 g) was put in a 100 ml-mass cylinder and gelled in a thermostat at

36.5°C. The apparatus for measuring gel strength (weight: 35 g) was then placed onto the

gelled poloxamer. The gel strength was determined by the time in (seconds) it took to move

the apparatus 5 cm down through the poloxamer gel (Schmolka, 1972). In cases that took

more than 10 min to drop the apparatus into the gel, various weights were placed on top of

the apparatus and gel strength was described by the minimal weights that pushed the

apparatus 5 cm down through the gel.[15]

Determination of the Mucoadhesive Force

The mucoadhesive force, the detachment stress of the liquid suppositories was determined

using a modification of the mucoadhesive force measuring device used by Choi et al. A

section was cut from the fundus of sheep rectum and instantly secured with the mucosal side

out into each glass vial. The vials were stored at 36.5°C for 10 min. 1 vial connected to the

that the gel is placed between the mucosal sides of both vials. Water was added to beaker.

Increasing weight of water added gradually would detach the two vials. Mucoadhesive force,

the detachment stress (dyne/cm²), is determined from the minimal weights of water that

detached the 2 vials.[16]

In Vitro Dissolution Test

Studies of PMZ HCl release from liquid suppository formulations were performed for

formulas (F6 ,F9-F12) using the in vitro dialyzing method in which 5ml of the prepared

liquid suppository formulation was syringed into a glass container closed at one end and the

open end covered by a 1.8 cm cap in diameter of hydrophilic membrane of regenerated

cellulose Millipore 0.45μ (soaked for 1 hr. before the test in the phosphate buffer), [17]

and

heated at 33 ± 1°C for 10 min to gelate completely.[18]This glass apparatus was fixed on the

paddle with cable ties, on dissolution apparatus type 2 and 500ml phosphate buffer pH 6.8

was used as a dissolution medium, within a period of 3hr and 50 rpm at 37°C. Aliquots (5ml)

were taken at regular intervals and analyzed spectrophotometerically at 248 nm.[17]

Kinetics Analysis of Drug Release

To analyze the mechanism of drug release from the prepared formulas, In vitro dissolution data were fitted to zero order, first order, Higuchi release model, and Korsmeyer Peppas

model and the model with the higher correlation coefficient was considered to be the best

model.[19]

RESULTS AND DISCUSSION

Evaluation of PMZ HCl Liquid Suppositories Gelation Temperature

Gelation temperature is the temperature at which the liquid phase makes a transition to gel. A

gelation temperature range suitable for liquid suppository would be 30–36°C. If the gelation

temperature of liquid suppository is lower than 30°C, gelation occurs at room temperature

leading to difficulty in manufacturing, handling and administering. If the gelation

temperature is higher than 36°C, the suppository still stays as a liquid at body temperature,

resulting in leakage from the anus.

Therefore, liquid suppository must have the suitable gelation temperature between 30–36°C,

Gelation temperatures of various preparations (F1-F13) and the obtained results are

summarized in table 2.

Table 2: Gelation Temperature of Prepared Formulas

Formula No Gelation Temperature oC

F1 50

F2 50

F3 28

F4 26

F5 19

F6 34

F7 32

F8 30

F9 32

F10 31

F11 30

F12 29

F13 18

PMZ HCl liquid suppository formulae (F1-F5) were prepared to study the effect of increasing

the concentrations of poloxamer P407 alone on gelation temperature. While formulae (F6-F8)

were prepared to study the effect of increasing poloxamer P188 concentration from 4 to 12 %

w/v, while fix the concentration of poloxamer P407 (16 % w/v) on gelation temperature.

.Formulas (F9-F12) were prepared to study the effect of addition and increasing the

concentrations of HPMCK4M from 0.5 to 2 %, while fix the concentration of poloxamer

P407 (16 % w/v) and poloxamer P188 (4 % w/v) on gelation temperature. Finally F13 were

prepared to study the effect of the addition of drug on gelation temperature.

For formulas (F1-F5) which prepared by increasing the concentration of poloxamer P407

from 12 % to 20%, the gelation temperatures were determined. The results as illustrated in

figure 1 show that as the concentration of poloxamer P407 increases the gelation temperature

decreases significantly (p<0.05). The decrease in the gelation temperature (from 50 to 19 oC)

with increasing P407 concentration may be attributed to the higher number and volume

occupied by micelles at lower temperatures. As the concentration increases, the gel structure

Figure 1: Effect of p 407 concentration on gelation temperature

It is important to note that PMZ HCl liquid suppositories composed of 16% P407 showed

intermediate gelation temperatures (28oC) so it is good candidate for gelation temperature

modulation using P188.

The previous results indicate that P407 alone could not provide gelation at the physiological

temperature. A modulation of the gelation temperature to reach the desired range (30-36oC)

could be accomplished by the use of a combination of the two poloxamer grades P407 and

P188, so we use mixture of poloxamers P407 and P188 in different ratios (16/4, 16/8 and

16/12) which showed a gelation temperature of 34°C, 32 oC and 30 oC, respectively.

By studying the effect of increasing the concentration of P188 on constant concentration of

P407 solution, it was found that the increasing in P188 concentration was accompanied by a

significant (p<0.05) decrease in the gelation temperature of the P407 solutions as shown in

figure 2. This is mainly attributed to the participation of P188 in the micellization process.[21]

In the present study, a combination of 16% P407 and 4% P188 was used for further

formulations with the addition of different concentrations of HPMC (0.5, 0.75, 1, and 2%

w/v).

The results showed that the addition of HPMC results in lowering the gelation temperature of

the resultant liquid suppositories. The impact of HPMC on the gelation temperature and gel

strength was found to be depending on their concentration. Increasing the concentration of

HPMC from 0.5 to 2 % w/v as shown in figure 3 produced a significant (p<0.05) decrease in

the gelation temperature and increase in the gel strength of the corresponding liquid

suppositories.

Figure 3: Effect of HPMCK4M concentration on gelation temperature

The gelation temperature lowering and gel strength increasing effect of mucoadhesive

polymers as HPMC could be explained by their ability to bind to the polyoxyethylene chains

present in the poloxamer molecules through hydrogen bonds. This will promote dehydration

causing an increase in entanglement of adjacent molecules and extensively increasing

The incorporation of 12.5 % w/v PMZ HCl increased the gelation temperature. This is due to

that water soluble substances cause modification of the process of micellar association of

poloxamer solutions leading to an increase in gelation temperature.[11]

Figure 3: Effect of drug on gelation temperature

Gel Strength

In the development of liquid suppository, the gel strength is important in finding the

condition which allows the easy insertion of the suppositories and no leakage from the anus.

At high gel strength, it is difficult to insert the suppositories. On the other hand, at low gel

strength the suppositories would leak from the anus. It has been reported that the optimal in

situ gelling and mucoadhesive liquid suppositories must have suitable gel strength, in the

range of 10 to 50 seconds.[23]

The gel strength is related to the internal structure and the strength of the physical or

chemical bonds forming the interplaying network of the long chains of the polymers involved

in gel formation, it resembles consistency and is related to viscosity and depends on the type

of polymer used.[24]

The results of gel strength for formulas (F6 ,F9-F12) shown in table (3) reveal that the

addition of the mucoadhesive polymer (HPMCK4M) increased the gel strength of

poloxamer mixture significantly (p < 0.05) in a concentration dependent manner. The

mechanism of the increase might be related to hydrogen bonding between poloxamer and the

Table 3: Gel Strength of the Prepared Formulas

Formula No Gel strength(seconds)

F6 15

F9 32

F10 36

F11 40

F12 57

Mucoadhesive Force

Mucoadhesive force is known to be dependent on the nature and the concentration of

mucoadhesive polymers. The stronger the mucoadhesive force is, the more it can prevent the

gelled suppositories from reaching the end of the colon, the pathway for the first-pass effect.

But if the mucoadhesive force is too excessive, the gel can damage the rectal mucous

membrane.[26] Therefore, liquid suppository must have the suitable mucoadhesive force.

The results of mucoadhesive force for formulas (F6, F9-F12) are shown in table (4) and

reveled that F6 which has poloxamer mixture only has low mucoadhesive force.

The addition of mucoadhesive polymer (HPMC) in (F9-F12) reinforced the mucoadhesive

force of rectal suppositories which has increased significantly (p<0.05) as the concentration

of mucoadhesive polymer increased over the range of 0.5-2%. Such effects on the

mucoadhesive force might be due to the binding of these polymers with the oligosaccharide

chains of rectal mucous lining.[27]

Table 4: Mucoadhesive Strength of Prepared Formulas

Formula No Mucoadhesive strength ( dyne/cm2 x 103 )

F6 0.867

F9 5.85

F10 10.4

F11 15.61

F12 23.4

Release Studies

Five PMZ HCl liquid suppositories passed the gelation temperature and gel strength tests

(F6, F9-F12) were subjected to the dissolution test.

Compared to the control gel (F6) that showed the fastest release among other formulas ( 98

% in 120 minutes) , the release was decreased significantly by addition of mucoadhesive

mucoadhesive polymer could be attributed to their ability to increase the overall product

viscosity [28] as well as their ability to distort or squeeze the extra-micellar aqueous channels

of poloxamer micelles through which the drug diffuses thereby delaying the release

process.[15]

Figure 4: Effect of addition of mucoadhesive polymer on drug release

Table 5: Release Kinetic of PMZ HCl from Different Suppository Frmulas Order of

reaction Formula

Number

Correlation coefficient (r2) Korsmeyer Pappas

Zero First Higuchi n r2

F6 0.9751 0.8978 0.9929 0.0139 0.9957

F9 0.862 0.9731 0.9314 0.4577 0.9377

F10 0.8384 0.966 0.9148 0.4598 0.9247

F11 0.7923 0.9169 0.881 0.453 0.9016

F12 0.8528 0.9521 0.9258 0.5192 0.9257

Analysis of Release Kinetic

Table (5) illustrated the correlation of dissolution data to different models of release kinetic,

where a good fitting to zero order model was observed with F6 while a good fitting to first

order model was observed with F9-F12, indicated by highest regression value (r2).

For Korsmyer-Pappas model, the value of release exponent (n) defines the release

mechanism, the n value of F6 shows n value less than 0.45 pointing a Fickian diffusion

polymeric chains.[30] F 9-F12 are between 0.45 to 0.89 indicating anomalous(non–Fickian)

transport which refer to combination of diffusion and erosion controlled drug release.[31]

CONCLUSION

In this study, an in situ gelling thermoreversible liquid suppository of PMZ HCl was

developed using poloxamer P407, poloxamer P188 and mucoadhesive polymer HPMCK4M.

In order to obtain liquid systems at room temperature which can be conveniently handled and

administered and that develop an intimate contact with the rectal mucosa, the gelation

temperatures of PMZ HCl rectal formulations was modulated to adjust the gelation just

below the body temperature. Based on the obtained results, it was concluded that

P407/P188/HPMC (16/4/0.5 % w/v) and P407/ P188/ HPMC (16/4/0.75 %w/v) that were

used in formulae F9 and F10, respectively, were selected as the bases of choice for PMZ HCl

liquid suppository since they exhibited optimum physical properties like gelation

temperature, gel strength, high mucoadhesive force and a moderate PMZ HCl in-vitro

release. Therefore, these gels represent a promising alternative to conventional suppositories

and might be applicable for the development of in situ gelling and mucoadhesive liquid

suppository for humans as a more convenient and effective rectal dosage form.

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