CHAPTER 7 SUMMARY AND CONCLUSIONS. constitutes the objective of many a research project in the field of pharmaceutical

Transcription

1 CHAPTER 7 SUMMARY AND CONCLUSIONS Taste masking and development of palatable dosage forms of bitter drugs constitutes the objective of many a research project in the field of pharmaceutical technology. Many fluoroquinolone drugs are highly bitter in taste. Norfloxacin and ciprofloxacin HCl are broad spectrum antibiotics, active against both Grampositive and Gram negative bacteria. These drugs are highly bitter in taste. The present investigation was undertaken with an overall objective of studying the drug resin complexation (DRC) and solid dispersion to mask the bitter taste of the drugs. Two resins, namely, Indion 414 (weak acid cation exchanger) & Indion 254 (strong acid cation exchanger) and stearic acid and PEG 1500 and two drugs, namely, norfloxacin and ciprofloxacin HCl were selected for the study of feasibility of employing drug resin complexation and solid dispersion for masking the bitter taste of drugs. The main objectives of this research project were to study the drug resin complexation & solid dispersion of norfloxacin and ciprofloxacin HCl and to formulate & evaluate orally disintegrating tablets & dry syrup of these drug resin complexes and solid dispersions for pediatrics. An extensive survey of recent literature was carried out on the subjects of Indion 414 and Indion 254, stearic acid and PEG 1500, norfloxacin and ciprofloxacin HCl and fast dissolving tablets and dry syrup. This literature survey established that there is a necessity to improve the palatability of norfloxacin and ciprofloxacin HCl, that complexation with resins and solid dispersion of stearic acid and PEG 1500 is an ideal method to mask the bitter taste and that formulation of fast dissolving tablets and dry 356

2 syrup is a good option to achieve the objective of palatable dosage forms of fluoroquinolones for pediatrics. UV spectrophotometric methods were utilized for the development of calibration curves for norfloxacin and ciprofloxacin HCl. New HPLC methods were developed for the estimation of norfloxacin and ciprofloxacin HCl in rabbit plasma. These methods were developed and validated and the total run time was set at 7 minutes and 6 minutes for norfloxacin and ciprofloxacin HCl respectively. The dissolution medium selected was 0.1 N HCl. Taste evaluation was carried out after obtaining the permission from the Institutional Ethics Committee for Research on Human Volunteers of Andhra University. Certificate number 56 is enclosed. Drug resin complexes (DRCs) of norfloxacin and ciprofloxacin HCl with Indion 414 in 1:1, 1:2 and 1:3 ratios were prepared and the effects of drug-resin ratio, ph, resin activation and stirring time on complex formation were evaluated. There was no significant loss of drug during the preparation of drug resin complexes in 1:3 ratio and its taste masking ability was better when compared to other proportions. Hence 1:3 ratio was used for further studies. Drug resin complexation was enhanced with increasing ph from 3 to 6.5. A maximum percentage of drug loading was obtained at ph 6.5. Above ph 6.5, the percentage of drug loading was decreased. The decreased complexation at lower ph is due to excess H + ions in the solution, which have more binding affinity to the COO - groups of resin and compete with the drug for binding.the percentage of drug loading efficiency of acid activated resin was more compared to inactivated resin. In inactivated resin matrix, the exchangeable groups are latent and coiled towards the back bone, hence 357

3 less drug loading efficiency. The resin activation exposed the exchangeable groups producing rapid drug exchange and hence higher drug binding. The percentage of the drug loading was increasing with the stirring time up to three hours. After three hours of stirring there was no significant increase in percentage of drug loading. It indicates three hours contact time between drug and resin is optimimum to equilibrate the ion exchange process to achieve maximum drug loading. Dissolution rate and dissolution efficiency were evaluated for complexes made with 1:3 ratio. Drug resin complexes (DRCs) of norfloxacin and ciprofloxacin HCl with Indion 254 in 1:1, 1:2 and 1:3 ratios were prepared and the effects of drug-resin ratio, ph, resin soaking time, and stirring time on complex formation were evaluated. Similar results of Indion 414 are observed for effects of drug-resin ratio, ph, and stirring time on complex formation with Indion 254. The percentage of the drug loading was increasing with the soaking time up to 30 minutes. After 30 minutes of soaking there was no significant increase in percentage of drug loading. In non soaking resin matrix, the exchangeable groups are latent and coiled towards the back bone, hence less drug loading efficiency. The resin soaking exposed the exchangeable groups producing rapid drug exchange and hence higher drug binding. Dissolution rate and dissolution efficiency were evaluated for complexes made with 1:3 ratio. DRCs of norfloxacin & ciprofloxacin HCl with Indion 414 & Indion 254 and solid dispersion of stearic acid & PEG 1500 were studied by DSC, XRD, SEM and FTIR studies. DSC & XRD indicated better drug inclusion in DRC. A stronger drug amorphization and entrapment in DRC was observed. SEM studies indicated good physical interaction of drug particles with Indion 414 and Indion 254. The crystalline 358

4 character of the drug was lost and the components of the system (i.e., drug and resin) could not be differentiated. FT-IR studies indicated that there would be a possibility of chemical modification in the DRC without any changes in basic nucleus of the drug. The drug release from DRC prepared with Indion 414 is faster whereas with Indion 254, it is slower. Solid dispersions of norfloxacin with stearic acid and PEG 1500 in 1:1:0, 1:1:0.2, 1:1:0.3, 1:1:0.4, 1:1:0.6, 1:1:0.8 and 1:1:1 ratios were prepared by fusion method. 1:1:1 ratio of norfloxacin-stearic acid-peg 1500 exhibited higher rates of dissolution and dissolution efficiency values than1:1:0, 1:1:0.2, 1:1:0.3, 1:1:0.4, 1:1:0.6 and 1:1:0.8. The hydrophilic polymer (PEG 1500) gave a marginal increase in the dissolution rate of norfloxacin. Addition of hydrophilic polymer (PEG 1500) to stearic acid has further enhanced the dissolution rate and efficiency (DE) of norfloxacin from solid dispersions. The dissolution data obeyed first order kinetic model as well as Hixson-Crowell s cube root model. The K 1 and DE 30% values increased as the proportion of PEG1500 in the solid dispersion system was increased in each case. Taste evaluation of solid dispersions in healthy human volunteers confirmed that the taste of norfloxacin was successfully masked by solid dispersion, prepared with stearic acid and PEG 1500 in all ratios. All the volunteers reported that all solid dispersions were tasteless and agreeable for a period of 10 minutes. 1:1:1 ratio of norfloxacin-stearic acid-peg 1500 was selected for the preparation of dry syrup because of higher rates of dissolution. Solid dispersions of ciprofloxacin HCl-stearic acid-peg 1500 in 1:1:0, 1:1:0.2, 1:1:0.3, 1:1:0.4, 1:1:0.6 and 1:1:0.8 ratios were prepared by fusion method. 1:1:0.8 ratio of ciprofloxacin HCl-stearic acid-peg 1500 exhibited higher rates of dissolution and 359

5 dissolution efficiency values than1:1:0, 1:1:0.2, 1:1:0.3, 1:1:0.4 and1:1:0.6. The hydrophilic polymer (PEG 1500) gave a marginal increase in the dissolution rate of ciprofloxacin HCl. Addition of hydrophilic polymer(peg 1500) to stearic acid has further enhanced the dissolution rate and efficiency (DE) of ciprofloxacin HCl in solid dispersions. The dissolution data obeyed first order kinetic model as well as Hixson- Crowell s cube root model. The K 1 and DE 30% values increased as the proportion of PEG1500 in the solid dispersion system was increased in each case. Taste evaluation of solid dispersions in healthy human volunteers confirmed that the taste of ciprofloxacin HCl was successfully masked by solid dispersion with stearic acid and PEG 1500 in all ratios. All the volunteers reported that all solid dispersions were tasteless and agreeable for a period of 10 minutes. 1:1:0.8 ratio of ciprofloxacin HCl-stearic acid-peg 1500 was selected for the preparation of dry syrup because of higher rates of dissolution. For the two drug solid dispersions of norfloxacin and ciprofloxacin HCl with stearic acid & PEG 1500, DSC & XRD indicated better drug inclusion in solid dispersion. SEM studies indicated good physical interaction of drug particles with stearic acid and PEG The crystalline character of the drug was lost and the components of the system (i.e., Norfloxacin/Ciprofloxacin HCl, stearic acid and PEG 1500) could not be differentiated. FT-IR studies indicated that there would be a possibility of chemical modification in the solid dispersions without any changes in basic nucleus of the drug. Norfloxacin and ciprofloxacin HCl, when administered in the form of conventional tablets or dry syrups, result in poor patient compliance, because of their bitter taste. Development of orally disintegrating tablets (ODT) or dry syrup of drug resin complexes (Indion 414 or Indion 254) or solid dispersions (Stearic acid and PEG 1500) 360

6 of norfloxacin and ciprofloxacin HCl is a good strategy to enhance patient compliance of these drugs. ODTs were developed by direct compression. In the direct compression method, mannitol was used as a diluent, and sodium starch glycolate (SSG) & crospovidone (CPV) as superdisintegranting agents at four concentrations (4.67, 7.33, 8.67 and 10%) with the drug in a drug resin complex form. The drug resin complex, the diluents, the superdisintegranting agents and other excipients were directly compressed into an ODT. When all the formulations thus produced were evaluated, it emerged that crospovidone (CPV) at 10% w/w in the tablets was giving the best drug release profile. These results may be due to the concentration of crosspovidone used and its swelling property. Dry syrup was prepared by passing all the ingredients through 60-mesh sieve. Norfloxacin and ciprofloxacin HCl dry syrup formulations were prepared by using sorbitol, erythroitol & aspartame as sweeting agents and sodium carboxymethyl cellulose & xanthan gum as suspending agents at different concentrations with the drug in a drug resin complex form or solid dispersion form. The formulated dry syrup was evaluated for drug content, taste of the syrup after reconstitution, ph of the syrup, sedimentation volume, specific gravity and dissolution characteristics. The sedimentation volume and redispersiblity was more for the dry syrups (NRDS04 & CRDS04) containing 3.37% of xanthan gum. The dissolution of the drug from the reconstituted syrup follows first order kinetics. Among all the formulations (ODTs & dry syrups) NRDS04 & CRDS04 were found to be better formulations respectively for norfloxacin and ciprofloxacin HCl 361

7 because of high dissolution rate, taste masking & disintegration. These two formulations, NRDSO 4 and CRDS04 may be exhibiting these results due to the following reasons. 1. Indion 414 has taste masking and super disintegrating characteristics which result in increased dissolution rate. Indion 254 (strong acid cation exchanger) bestowed slow drug release to the formulations because it binds with drug strongly when compared to Indion 414(weak acid cation exchanger). 2. The concentration and nature of the xanthan gum used in these formulations, NRDS04 & CRDS04, impart desirable viscousity, optimum sedimentation volume, ease of redispersibility and increased dissolution rate when compared to other liuid formulations. Stability studies of selected, optimized formulations of norfloxacin and ciprofloxacin HCl dry syrups were carried out as per ICH guidelines. These studies indicated that optimized syrups, NRDS04 & CRDS04, developed in this research project are stable under accelerated conditions of temperature and humidity. Animal housing and handling were in accordance with the CPCSEA guide lines. This study on animals were carried out in the pharmacology laboratories of the University College of Pharmaceutical Sciences, Andra university, which is approved by the institutional ethics committee and CPCSEA (Regd. No / A/ CPCSEA) for experimentation on animals. Pharmacokinetic studies were carried out on the developed optimized dry syrups, NRDS04 & CRDS04 in comparison with marketed conventional formulations. The in vivo experiments were carried out in healthy rabbits of either sex weighing (1.0 ± 0.2 kg) were divided into 2 groups, each consisting of 6 animals. 362

8 All the pharmacokinetic parameters of absorption, namely, K a, C max, T max, percent absorbed, AUC and AUMC indicated similar absorption and bioavailability of experimental formulations (NRDS04 & CRDS04) with that of commercial formulations. The pharmacokinetic data was subjected to statistical analysis (P<0.05). The results of statistical analysis indicated no significant difference in C max, T max, K a, K e, t 1/2, MRT, percent absorbed, AUC and AUMC values among commercial formulations and experimental formulations. So, it may be concluded, that the experimental formulations, NRDS04 & CRDS04, of norfloxacin and ciprofloxacin HCl, respectively, are having similar absorption and bioavailability in comparison with the commercial products and shows more superior in its palatability due to drug resin complex. Thus, the objectives of this research project could be achieved by the development of taste masked ODTs and dry syrups by using cation resins (Indion 414 and Indion 254) or solid dispersion of stearic acid and PEG 1500 are suitable for the preparations of pediatric palatable formulations of norfloxacin and ciprofloxacin HCl. From the results obtained the following conclusions are drawn. 1) Indion 414 can be used for taste masking and for formulating fast release products. 2) Indion 254 can be used for taste masking and for formulating slow release products. 3) Solid dispersions of stearic acid and PEG 1500 can be used for taste masking and for formulating slow release products. 363