The colon is being viewed as a promising site of drug delivery owing to its long transit time (up to 78 hrs), which is likely to increase the time available for drug absorption. Progesterone (PG) has a short elimination half-life (~19-95 min) and undergoes extensive first-pass hepatic metabolism which results in very low oral bioavailability (~25%). The aim of this work was to study the feasibility of preparing PG-loaded colon-targeted microparticles (MP's) to overcome the shortcomings associated with the oral administration of PG. MP's were prepared by the modified ionotropic gelation technique using sodium carboxymethylcellulose (NaCMC)/pectin mixture as a biodegradable matrix, zinc acetate and aluminum sulfate as cross-linkers. A 24 full factorial design was carried out to optimize the experimental conditions with the investigated factors being: polymer concentration (X¬1), drug concentration (X2), Zn(CH3COO)2 concentration (X3) and Al2(SO4)3 concentration (X4). The prepared MP's were investigated under conditions mimicking mouth-to-colon transit and the effect of the afore-mentioned factors on the release and surface characteristics of MP's has been studied. The results obtained implied that, regardless of the concentration of cross-linking agents, the polymer and drug concentrations exhibited the greatest influence on the drug entrapment efficiency (EE), which decreased as the drug concentration decreased from 1 to 0.5% w/v (95.13% and 83.88% respectively) and as the polymer concentration increased from 1.25 to 1.5% w/v (107.35% and 95.13% respectively). On the other hand, MP's prepared with 1% drug showed a significantly slower release rate than those prepared with 0.5% drug as indicated by the values of Mean Dissolution Time (MDT) & the release rate constant(k). This study confirms the viability of the prepared microparticles as a colon-targeted drug delivery system.

The colon is being viewed as a promising site of drug delivery owing to its long transit time (up to 78 hrs), which is likely to increase the time available for drug absorption. Progesterone (PG) has a short elimination half-life (~19-95 min) and undergoes extensive first-pass hepatic metabolism which results in very low oral bioavailability (~25%). The aim of this work was to study the feasibility of preparing PG-loaded colon-targeted microparticles (MP's) to overcome the shortcomings associated with the oral administration of PG. MP's were prepared by the modified ionotropic gelation technique using sodium carboxymethylcellulose (NaCMC)/pectin mixture as a biodegradable matrix, zinc acetate and aluminum sulfate as cross-linkers. A 24 full factorial design was carried out to optimize the experimental conditions with the investigated factors being: polymer concentration (X¬1), drug concentration (X2), Zn(CH3COO)2 concentration (X3) and Al2(SO4)3 concentration (X4). The prepared MP's were investigated under conditions mimicking mouth-to-colon transit and the effect of the afore-mentioned factors on the release and surface characteristics of MP's has been studied. The results obtained implied that, regardless of the concentration of cross-linking agents, the polymer and drug concentrations exhibited the greatest influence on the drug entrapment efficiency (EE), which decreased as the drug concentration decreased from 1 to 0.5% w/v (95.13% and 83.88% respectively) and as the polymer concentration increased from 1.25 to 1.5% w/v (107.35% and 95.13% respectively). On the other hand, MP's prepared with 1% drug showed a significantly slower release rate than those prepared with 0.5% drug as indicated by the values of Mean Dissolution Time (MDT) & the release rate constant(k). This study confirms the viability of the prepared microparticles as a colon-targeted drug delivery system.

The colon is being viewed as a promising site of drug delivery owing to its long transit time (up to 78 hrs), which is likely to increase the time available for drug absorption. Progesterone (PG) has a short elimination half-life (~19-95 min) and undergoes extensive first-pass hepatic metabolism which results in very low oral bioavailability (~25%). The aim of this work was to study the feasibility of preparing PG-loaded colon-targeted microparticles (MP's) to overcome the shortcomings associated with the oral administration of PG. MP's were prepared by the modified ionotropic gelation technique using sodium carboxymethylcellulose (NaCMC)/pectin mixture as a biodegradable matrix, zinc acetate and aluminum sulfate as cross-linkers. A 24 full factorial design was carried out to optimize the experimental conditions with the investigated factors being: polymer concentration (X¬1), drug concentration (X2), Zn(CH3COO)2 concentration (X3) and Al2(SO4)3 concentration (X4). The prepared MP's were investigated under conditions mimicking mouth-to-colon transit and the effect of the afore-mentioned factors on the release and surface characteristics of MP's has been studied. The results obtained implied that, regardless of the concentration of cross-linking agents, the polymer and drug concentrations exhibited the greatest influence on the drug entrapment efficiency (EE), which decreased as the drug concentration decreased from 1 to 0.5% w/v (95.13% and 83.88% respectively) and as the polymer concentration increased from 1.25 to 1.5% w/v (107.35% and 95.13% respectively). On the other hand, MP's prepared with 1% drug showed a significantly slower release rate than those prepared with 0.5% drug as indicated by the values of Mean Dissolution Time (MDT) & the release rate constant(k). This study confirms the viability of the prepared microparticles as a colon-targeted drug delivery system.

The colon is being viewed as a promising site of drug delivery owing to its long transit time (up to 78 hrs), which is likely to increase the time available for drug absorption. Progesterone (PG) has a short elimination half-life (~19-95 min) and undergoes extensive first-pass hepatic metabolism which results in very low oral bioavailability (~25%). The aim of this work was to study the feasibility of preparing PG-loaded colon-targeted microparticles (MP's) to overcome the shortcomings associated with the oral administration of PG. MP's were prepared by the modified ionotropic gelation technique using sodium carboxymethylcellulose (NaCMC)/pectin mixture as a biodegradable matrix, zinc acetate and aluminum sulfate as cross-linkers. A 24 full factorial design was carried out to optimize the experimental conditions with the investigated factors being: polymer concentration (X¬1), drug concentration (X2), Zn(CH3COO)2 concentration (X3) and Al2(SO4)3 concentration (X4). The prepared MP's were investigated under conditions mimicking mouth-to-colon transit and the effect of the afore-mentioned factors on the release and surface characteristics of MP's has been studied. The results obtained implied that, regardless of the concentration of cross-linking agents, the polymer and drug concentrations exhibited the greatest influence on the drug entrapment efficiency (EE), which decreased as the drug concentration decreased from 1 to 0.5% w/v (95.13% and 83.88% respectively) and as the polymer concentration increased from 1.25 to 1.5% w/v (107.35% and 95.13% respectively). On the other hand, MP's prepared with 1% drug showed a significantly slower release rate than those prepared with 0.5% drug as indicated by the values of Mean Dissolution Time (MDT) & the release rate constant(k). This study confirms the viability of the prepared microparticles as a colon-targeted drug delivery system.

The colon is being viewed as a promising site of drug delivery owing to its long transit time (up to 78 hrs), which is likely to increase the time available for drug absorption. Progesterone (PG) has a short elimination half-life (~19-95 min) and undergoes extensive first-pass hepatic metabolism which results in very low oral bioavailability (~25%). The aim of this work was to study the feasibility of preparing PG-loaded colon-targeted microparticles (MP's) to overcome the shortcomings associated with the oral administration of PG. MP's were prepared by the modified ionotropic gelation technique using sodium carboxymethylcellulose (NaCMC)/pectin mixture as a biodegradable matrix, zinc acetate and aluminum sulfate as cross-linkers. A 24 full factorial design was carried out to optimize the experimental conditions with the investigated factors being: polymer concentration (X¬1), drug concentration (X2), Zn(CH3COO)2 concentration (X3) and Al2(SO4)3 concentration (X4). The prepared MP's were investigated under conditions mimicking mouth-to-colon transit and the effect of the afore-mentioned factors on the release and surface characteristics of MP's has been studied. The results obtained implied that, regardless of the concentration of cross-linking agents, the polymer and drug concentrations exhibited the greatest influence on the drug entrapment efficiency (EE), which decreased as the drug concentration decreased from 1 to 0.5% w/v (95.13% and 83.88% respectively) and as the polymer concentration increased from 1.25 to 1.5% w/v (107.35% and 95.13% respectively). On the other hand, MP's prepared with 1% drug showed a significantly slower release rate than those prepared with 0.5% drug as indicated by the values of Mean Dissolution Time (MDT) & the release rate constant(k). This study confirms the viability of the prepared microparticles as a colon-targeted drug delivery system.

Chitosan microspheres has been in the focus of increasing interest as polymeric drug carriers due to their appealing properties such as biocompatibility, biodegradability, low toxicity, mucoadhesion and relatively low cost of production. Gel formation can be obtained by interactions of chitosan with low molecular weight counter-ions such as polyphosphates. However, one drawback of using this natural polysaccharide for oral controlled release dosage forms is its fast dissolution rate in the stomach. Since chitosan is positively charged at low pH values (below its pKa value), it spontaneously associates with polyanions to form polyelectrolyte complexes (PEC). These PEC exhibit favorable physicochemical properties with preservation of chitosan's biocompatible characteristics. These complexes are therefore good candidates for the design of colon-targeted dosage forms. Various techniques are used for preparing chitosan microspheres which have been reviewed. This review also includes factors that affect the release characteristics of drugs from chitosan microspheres.

Chitosan microspheres has been in the focus of increasing interest as polymeric drug carriers due to their appealing properties such as biocompatibility, biodegradability, low toxicity, mucoadhesion and relatively low cost of production. Gel formation can be obtained by interactions of chitosan with low molecular weight counter-ions such as polyphosphates. However, one drawback of using this natural polysaccharide for oral controlled release dosage forms is its fast dissolution rate in the stomach. Since chitosan is positively charged at low pH values (below its pKa value), it spontaneously associates with polyanions to form polyelectrolyte complexes (PEC). These PEC exhibit favorable physicochemical properties with preservation of chitosan's biocompatible characteristics. These complexes are therefore good candidates for the design of colon-targeted dosage forms. Various techniques are used for preparing chitosan microspheres which have been reviewed. This review also includes factors that affect the release characteristics of drugs from chitosan microspheres.

Chitosan microspheres has been in the focus of increasing interest as polymeric drug carriers due to their appealing properties such as biocompatibility, biodegradability, low toxicity, mucoadhesion and relatively low cost of production. Gel formation can be obtained by interactions of chitosan with low molecular weight counter-ions such as polyphosphates. However, one drawback of using this natural polysaccharide for oral controlled release dosage forms is its fast dissolution rate in the stomach. Since chitosan is positively charged at low pH values (below its pKa value), it spontaneously associates with polyanions to form polyelectrolyte complexes (PEC). These PEC exhibit favorable physicochemical properties with preservation of chitosan's biocompatible characteristics. These complexes are therefore good candidates for the design of colon-targeted dosage forms. Various techniques are used for preparing chitosan microspheres which have been reviewed. This review also includes factors that affect the release characteristics of drugs from chitosan microspheres.

Chitosan microspheres has been in the focus of increasing interest as polymeric drug carriers due to their appealing properties such as biocompatibility, biodegradability, low toxicity, mucoadhesion and relatively low cost of production. Gel formation can be obtained by interactions of chitosan with low molecular weight counter-ions such as polyphosphates. However, one drawback of using this natural polysaccharide for oral controlled release dosage forms is its fast dissolution rate in the stomach. Since chitosan is positively charged at low pH values (below its pKa value), it spontaneously associates with polyanions to form polyelectrolyte complexes (PEC). These PEC exhibit favorable physicochemical properties with preservation of chitosan's biocompatible characteristics. These complexes are therefore good candidates for the design of colon-targeted dosage forms. Various techniques are used for preparing chitosan microspheres which have been reviewed. This review also includes factors that affect the release characteristics of drugs from chitosan microspheres.