title: Development of oral suspensions of microparticles of ethylcellulose with tramadol.
abstract: BACKGROUND
  Although tramadol has less analgesic power than morphine, it presents fewer side effects and consequently is currently considered as a drug of choice in the treatment of chronic pain. The objective of this work was to obtain a sustained-release liquid preparation for oral administration, using pseudolatex of ethylcellulose as a delivery vehicle of the active principle.
  
  
  METHODS
  Once an appropriate microencapsulation had been achieved, different formulations with different viscosing agents were designed and subsequently subjected to in vitro release studies, using Franz-type diffusion cells.
  
  
  RESULTS
  The pseudolatex with tramadol showed an encapsulation efficiency of 82% but was found to be dependent on the quantity of the drug. The images obtained through scanning electron microscopy showed sphere-shaped particles with a porous surface and diameter sizes of 3.5 and 5.5 microm. Infrared spectrophotometry and calorimetric analysis revealed the formation of a drug-polymer complex. Of the formulations proposed, that with xanthan gum released 46% of the drug, whereas Carbopol, sodium carboxymethylcellulose, and Avicel gave 50% and 55%, respectively. All followed a release kinetic of cube root, with the release mechanism of the active principle occurring through anomalous transport.
  
  
  CONCLUSIONS
  In accordance with the studies performed, we can confirm a liquid pharmaceutical preparation for oral use, capable of providing a sustained release of tramadol.
authors.affiliation: Department of Pharmacy and Pharmaceutical Technology, School of Pharmacy, University of Granada, Granada, Spain.
authors.forename: M E
authors.initials: ME
authors.lastname: Morales
authors.forename: M A
authors.initials: MA
authors.lastname: Ruiz
authors.forename: G
authors.initials: G
authors.lastname: López
authors.forename: V
authors.initials: V
authors.lastname: Gallardo
mesh_terms: D000284:Administration, Oral; D000701:Analgesics, Opioid / Q000008:administration & dosage* / Q000032:analysis / Q000737:chemistry; D002152:Calorimetry, Differential Scanning; D002482:Cellulose / Q000031:analogs & derivatives* / Q000737:chemistry; D003692:Delayed-Action Preparations / Q000008:administration & dosage / Q000032:analysis / Q000737:chemistry; D004058:Diffusion; D004337:Drug Carriers / Q000008:administration & dosage* / Q000032:analysis / Q000737:chemistry; D004339:Drug Compounding; D005079:Excipients / Q000737:chemistry; D007700:Kinetics; D008855:Microscopy, Electron, Scanning; D008863:Microspheres; D010316:Particle Size; D011135:Polysaccharides, Bacterial / Q000737:chemistry; D011145:Polyvinyls / Q000737:chemistry; D013499:Surface Properties; D013535:Suspensions; D014147:Tramadol / Q000008:administration & dosage* / Q000032:analysis / Q000737:chemistry; D014783:Viscosity
chemical_list: D000701:Analgesics, Opioid; D003692:Delayed-Action Preparations; D004337:Drug Carriers; D005079:Excipients; D011135:Polysaccharides, Bacterial; D011145:Polyvinyls; D013535:Suspensions; D014147:Tramadol; C013517:ethyl cellulose; D002482:Cellulose; C002563:xanthan gum