Development of oral suspensions of microparticles of ethylcellulose with tramadol

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 mu m. 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 (R), sodium carboxymethylcellulose, and Avicel (R) 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.