Health and service :: pharmaceutical production

Table 1. Formulation details and composition of the medium of two suspensions.  Materials Uses Amount in suspensions Suspension I Suspension II Simple syrup, NF Sweetening agent 1 Part 2 Parts Sorbitol syrup 70% Sweetening agent 1 Part 2 Parts Deionized distilled water Vehicle 3 Parts 1 part Tragacanth Suspending agent, Thickening agent 0.6% 0.6% Tween 80 Nonionic moisturizing agent 0.02% 0.02% Methyl paraben Preservative 0.1% 0.1% Propyl paraben Preservative 0.1% 0.1%    measuring tube No.2.   Sedimentation volume  The sedimentation volume (F) was obtained based on the following equation:  01VVF,   V1 is the equilibrium volume of sediment and V0 is the total volume of suspension before sedimentation. Equilibrium volume of sediment is the volume which remains unchanged for 3 weeks (Gennaro, 2000; Sinko, 2006).   Degree of flocculation  Degree of flocculation () was estimated using this equation:  FF,   F is the sedimentation volume of the flocculated suspension, and F is the sedimentation volume of the suspension when deflocculated (Gennaro, 2000; Sinko, 2006).  Ease of redispersibility: The number of shears required to redisperse a sedimented suspension in a cylindrical glass graduate is an indicator of ease of redispersibility (N) (Jones et al., 1970).   Freeze/Thaw cycles  Physical and microscopic changes of suspensions under sudden thermal changes were investigated. Suspensions were kept in a 40°C oven for 24 h and then transferred to a 0°C freezer for 24 h (Lieberman, 1990).   Normal temperature fluctuation  Inspection of physical and microscopic changes of the suspension during a gradual decrease in temperature from 40 to -5°C was also performed. For this purpose, suspensions were kept for 24 h in each temperature (Sinko, 2006).  pH of suspensions: pH of suspensions was determined using a Rotring pH meter (Dalal and Narurkar, 1991). Drug release studies  The USP paddle method was used for testing the release of theophylline from microcapsules and suspensions. Experiments were performed according to dissolution test No. II for sustained-release theophylline preparation using a USP dissolution apparatus (Pharma test, PTZWS3, Germany).   The dissolution medium was consisted of 900 ml phosphate buffer (pH 4.5) maintained at 37C stirred at rate of 75 rpm. An amount of microcapsule or suspension containing 100 mg theophylline was used for each dissolution experiment. At appropriate time intervals, 20, 40, 60, 90, 120, 180, 240, 300, 360, 420 and 480 min, a 3 ml sample of dissolution medium was withdrawn and replaced by an equal volume of medium to maintain the volume constant. Samples were filtered, diluted, and analyzed for theophylline concentration at 270 nm to characterize the dissolution profiles. For reading the absorbance of samples obtained from the dissolution of suspensions, dissolution media containing drug free suspension was used as the blank. Dissolution efficiency percentage after 8 h (DE8%) was considered as a basis for comparing the dissolution profiles. DE% was calculated based on the following equation:  100.%1000tydtyDEt  DE is the ratio of area under the dissolution curve at a given time to the total area at the same time once the entire content is released (Khan, 1975).   Kinetic models analysis  The release data were fitted to different kinetic models in Microsoft Excel 2007 software as follows to determine the model which better described the kinetics of the release behavior: First-order kinetic tkWW10lnln, Hixson-Crowell’s cube root of time tkWW23/103/1, and square-root of time 2/10ktWW, where W is the amount of drug remaining to be released and W0 is the initial amount of drug (Sprockel and Price, 1989).   Statistical analysis  SPSS software version 12 was used for all statistical analysis. Student t-test and one-way analysis of variance (ANOVA) followed by a Duncan post hoc test, was used for comparison between DE%

Health and service :: pharmaceutical production

emulsion-solvent  evaporation  for  terbutaline  (Cuña  et  al., 2000),  in-situ  gelation  for  theophylline  (Miyazaki  et  al., 2000), emulsion-solvent diffusion for ibuprofen (Kawashima  et  al.,  1991)  and  spray  drying  for  paclitaxel (Mu  et  al.,  2005).  Choosing  a  suitable  microencapsulation method  is  highly  dependent  on  the  drug  characteristics, type  of  polymer  used  and  economic  considerations. Emulsion-solvent  evaporation  technique  is  one  of  early methods  of  microencapsulation  which  has  been  widely studied  for  preparation  of  polymeric  microcapsules.  In this  technique,  a  polymer  solution  which  drug  substance is  dissolved  or  dispersed  in  is  emulsified  in  the  external phase.  By  evaporation  of  the  solvent,  polymeric  capsules are  formed  around  the  drug  particles.  The  size  and  state of  the  particle  in  the  internal  phase  play  an  important  role in  the  final  status  of  the  microparticles.  The  choice  of  the internal  and  the  external  phase  of  the  emulsion,  type  of emulsifier  and  method  of  homogenizing  two  phases  will effectively  determine  the  characteristics  of  the  final microparticles  (Matsumoto  et  al.,  2008).  Therefore,  the method  is  very  flexible  for  different  types  of  polymers  and hydrophilic  and  lipophilic  drugs,  and  by  selecting  suitable solvent  and  emulsifier;  various  combinations  of  drug substances  and  polymers  could  be  applied.  We  selected ethyl  cellulose  (EC)  as  the  sustaining  polymer  since  it  is  a water-insoluble  polymer  with  good  film  forming  ability, durability  and  low  cost  and  extended  drug  release properties  (Shi  et  al.,  2008;  2009).  EC  is  a  nonbiodegradable  and  biocompatible  and  gastro-resistant polymer  which  has  been  extensively  used  as  drug release  retardant  which  easily  forms  microcapsules  with a  one-step  encapsulation  method  (Das  and  Rao,  2006; Sudhamani  et  al., 2010). Taking  all  these  into  consideration,  we  aimed  at preparing sustained release microcapsules of theophylline  by  emulsion-solvent  evaporation  technique using  EC.  Although  theophylline  encapsulation  in  EC microspheres  for  sustained  delivery  have  been  reported in  several  studies  (Pachuau  et  al.,  2008;  Thakare  et  al., 2011),  incorporating  the  microcapsules  into  the suspension  base  was  not  reported  elsewhere.  The novelty  of  our  work  was  to  provide  a  microparticle containing  oral  liquid  sustained  release  dosage  form  for easy  use in pediatric  and  geriatric  patients. MATERIALS  AND  METHODS   The  following  materials  were  obtained  from  commercial  sources: EC  (ethoxy  content  46%,  Aldrich,  USA),  acetone,  dichloromethane, liquid  paraffin,  acacia,  ammonium  hydroxide  25%,  methyl  paraben, propyl  paraben,  sodium  lauryl  sulfate  (SLS),  theophylline  and sucrose  (Merck,  Germany),  sorbitol  syrup  70%  and  tragacanth (Modarres,  Iran).  All  other  chemicals  and  solvents  were  of  analytical grade. Preparation  of  microcapsules Microcapsules     were    prepared     by    emulsion-solvent     evaporation   technique  with  two  strategies.  First  strategy  was  based  on  an  oil-in- water  (o/w)  emulsion  which  prepared  after  examining  large  number of  variables.  For  preparing  the  oil  phase,  required  amount  of  EC  (in three  ratios  to  drug;  1,  2  and  3)  was  completely  dissolved  in dichloromethane  and  800  mg  theophylline  was  thoroughly dispersed  in  the  mixture  by  stirring.  The  oil  phase  was  emulsified into  the  aqueous  phase  (1.5%  SLS  solution  in  water)  under  stirring at  300  rpm.  The  resulting  emulsion  was  stirred  for  45  min  at  room temperature  to  remove  dichloromethane  completely.  The  formed microcapsules  were  filtered,  washed  and  dried  at  room temperature.   Second  strategy  was  based  on  emulsifying  the  drug-containing EC  solution  in  an  oil  phase.  The  optimum  condition  was  selected after  performing  a  set  of  experiments  and  evaluating  the  size  and drug  loading  percentage  of  the  particles.  The  internal  phase  of  the emulsion  contained  required  amount  of  theophylline  dispersed  in the  EC  solution  in  acetone.  The  internal  phase  was  then incorporated  into  the  external  phase  contained  1.3%  Tween  80  in 100  ml  liquid  paraffin.  The  mixture  was  stirred  at  room  temperature for  5h  to  remove  acetone  and  the  resulting  microcapsules  were then  filtered  and  washed  with  n-hexane  and  dried  at  room temperature.  Eight  formulations  (f1  to  f8)  were  prepared  by  this strategy  in  the  drug  to  polymer  ratios  of  1:1,  1:1.2,  1:1.3,  1:1.4, 1:1.5  and  1:2.   Morphological  studies  of  microcapsules In  order  to  demonstrate  the  formation  of  microcapsules  and preliminary  studies  of  their  shape,  resulting  microcapsules  were studied  using  a  simple  optical  microscope  (HM-LUX3,  Leitz, Germany).  Samples  of  microcapsules  were  selected  randomly.  Size of  microcapsules  was  also  determined  using  hemocytometer. Determination  of  drug  loading  of  microcapsules The  drug  content  of  microcapsules  was  determined  according  to USP  30  method  for  testing  content  uniformity  of  sustained-release capsules  of  theophylline  (USP,  2007).  Briefly,  a  sample  of microcapsules  containing  100  mg  of  drug  was  triturated  with  20  ml of  water,  transferred  to  a  100  ml  volumetric  flask,  25  ml  of  6  N ammonium  hydroxide  added,  sonicated  for  about  45  min,  and cooled  to  room  temperature.  The  mixture  was  diluted  to  volume  and mixed.  The  mixture  was  then  filtered  and  diluted  with  water  and  the absorbance  of  this  solution  and  a  standard  solution  of  theophylline, similarly  prepared  was  read  at  270  nm  with  ultraviolet  (UV)-visible spectrophotometer  (550SE,  Perkin-Elmer,  USA).  The  concentration of  drug  in  the  sample  was  then  determined  according  to  the standard  solution  of  theophylline. Preparation  of  suspensions Microcapsules  with  the  optimum  range  of  dissolution  (dissolution test  will  be  discussed  in  following  sections)  and  shape  were selected  to  be  formulated  in  suspensions.  Two  suspension formulations  were  prepared  as  the  medium  of  suspensions  (Table 1),  either  contains  100  mg  theophylline  /  5  ml  (Kawashima  et  al., 1991). Characterization  of  suspensions Rheology The  rheology  of  the  suspensions  was  determined  using  a  Brookfield rotational  viscometer  (Metler  RM180)  with  measuring  bob  No.2    and  

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Preparation  and evaluation  of  a  sustained-release suspension  containing  theophylline  microcapsules Jaber  Emami1,  Jaleh  Varshosaz1,  Mohammadreza  Amirsadri1  and Fatemeh  Ahmadi2,3* 1Department of  Pharmaceutics, Faculty  of  Pharmacy  and  Pharmaceutical  Sciences,   Isfahan  University  of  Medical  Sciences, Isfahan, Iran. 2Department of  Pharmaceutics, Faculty  of  Pharmacy,  Shiraz  University  of  Medical  Sciences,  Shiraz, Iran. 3Cardiovascular Research  Centre,  Fasa University  of  Medical  Sciences, Fasa,  Iran. Accepted  9  July,  2012 A  great  effort  has  been  devoted  to  the  preparation  of  sustained-release  formulations  of  theophylline  to prevent  large  fluctuations  of  serum  concentration  and  increasing  the  therapeutic  efficacy  followed  by patient  compliance.  In  the  present  study,  microcapsules  of  theophylline  with  ethyl  cellulose  (EC)  were prepared  by  emulsion-solvent  evaporation  method  in  different  polymer  to  drug  ratios.  Size, morphology,  drug  loading  and  release  behavior  of  microcapsules  were  also  studied.  Microcapsules were  then  formulated  into  suspensions  to  provide  an  oral  liquid  dosage  form  for  drug  and  resulting suspensions  were  examined  for  stability  and  release  characteristics  in  various  storage  times.  Results showed  that  microcapsules  prepared  in  drug  to  polymer  ratio  1:1.4  by  emulsifying  polymer  solution  in liquid  paraffin  presented  the  sustained-release  properties  which  met  the  United  States  Pharmacopeia (USP)  (2007)  requirements  (t50%  and  t80%  of  these  microparticles  were  150  and  360  min,  respectively). The  suspensions  prepared  by  these  microcapsules  were  also  stable  in  the  study  period  and  their release  profiles  were  consistent  to  the  original  microcapsules.  The  results  allow  for  the  conclusion  that the  formulated  suspension  can  be  used  as  a  sustained-release  formulation  for  theophylline  in  treatment of  obstructive pulmonary  disorders.         Key  words:  Theophylline,  microencapsulation,  suspension,  sustained-release,  ethyl  cellulose. INTRODUCTION Theophylline  is  a  methylxanthine  alkaloid  which  is  used as  bronchodilator  in  treatment  of  chronic  obstructive pulmonary  disorders  especially  asthma.  Although,  it  is used  for  about  70  years,  the  complications  associated with  its  use  are  still  unsolved  (Obeidat  et  al.,  2009;  Soni et  al.,  2010).  Theophylline  is  a  narrow  therapeutic  index drug  with  a  short  half-life.  Conventional  dosage  forms  of theophylline  should  be  administered  3  to  4  times  a  day  to provide  effective  concentration  and  to  avoid  large fluctuations  in  blood  concentration.  This  leads  to  poor patient  compliance  and  enhanced  risk  of  gastrointestinal (GI)  and  cardiovascular  adverse  effects.  Sustained- release     formulations      would       provide        steady       blood *Corresponding  author.  E-mail:  ahmadi_f@sums.ac.ir.  Tel:  +98 (711)  2424128  (Ext  272).  Fax:  +98  (711) 2424126. concentrations  with  minimum  fluctuation  and  results  in higher  therapeutic  efficacy  and  lower  risk  of  toxicity  (Roy et  al., 2007; Zhang  et  al., 2008). Among  sustained-release  drug  delivery  systems, microcapsules  have  received  much  attention  because  of uniform  distribution  in  GI  tract  which  leads  to  uniform absorption  and  decreasing  risk  of  local  effects  on  GI  tract. Another  advantage  of  microparticulate  systems  is  their feasibility  to  be  incorporated  into  liquid  dosage  forms such  as  suspensions.  In  addition  to  sustain  the  drug release,  microencapsulation  of  theophylline  can  decrease its  irritating  effect  on  GI  mucosa  and  mask  drug  taste (Lavasanifar  et  al.,  1997).  Due  to  ease  of  swallowing  and flexibility  in  dosage  adjustment,  liquid  dosage  forms  are preferred  especially  in  pediatric  and  geriatric  patients (Bodmeier  et  al.,  1991;  Cuña  et  al.,  2000).  Different techniques  of  microencapsulation  have  been  developed for       controlled      delivery     of     different    drugs     including