Release Studies

Strobel et al. (101) reported a unique approach to delivery of anticancer agents from lactide/glycolide polymers. The concept is based on the combination of misonidazole or adriamycin-releasing devices with radiation therapy or hyperthermia. Prototype devices consisted of orthodontic wire or sutures dip-coated with drug and polymeric excipient. The device was designed to be inserted through a catheter directly into a brain tumor. In vitro release studies showed the expected first-order release kinetics on the monolithic devices. 

D., Microencapsulation of nitrofurantoin in poly( e-caprolactone) Tableting and in vitro release studies, Int. J. Pharm.. 35. 145-156, 1987. 

After release there must be some way of terminating the action of a NT necessitating the presence of an appropriate enzyme and/or uptake mechanism. Such uptake processes can be quite specific chemically. Thus a high-affinity uptake (activated by low concentrations) can be found for glycine in the cord where it is believed to be a NT, but not in the cortex where is has no such action. This specific uptake can be utilised to map terminals for a particular NT, especially if it can be labelled, and also for loading nerves with labelled NT for release studies. 

Biodegradable poly(phosphoester-urethanes) containing bisglycophosphite as the chain extender were synthesized. Methylene bis-4-phenyl isocyanate (MDI) and toluene diisocyanate (TDI) were initially used as diisocyanates. Since there was a concern that the degradation products could be toxic, the ethyl 2,6-diisocyanatohexanoate (LDI) was synthesized and replaced the MDI (or TDI). The hydrolytic stability and solubility of these polymers were tested. Preliminary release studies of 5-fluorouracil from MDI based poly(phosphoester-urethane) and methotrexate from LDI based poly(phosphoester-urethane) are also reported. 

Chemical structure of monomers and intermediates was confirmed by FT-IR and FT-NMR. Molecular weight distribution of polymers was assessed by GPC and intrinsic viscosity. The thermal property was examined by differential scanning calorimetry. The hydrolytic stability of the polymers was studied under in vitro conditions. With controlled drug delivery as one of the biomedical applications in mind, release studies of 5-fluorouracil and methotrexate from two of these polymers were also conducted. 

This paper concerns the synthesis and characterization of amphiphilic networks comprising PHEMA and PIB segments. Sustained release studies with theophylline-loaded networks are also described. 

A Brodin, A Nyqvist-Mayer. In vitro release studies on lidocaine aqueous solutions, micellar solutions, and o/w emulsions. Acta Pharm Suec 19 267-284, 1982. 

Martin, G.P. and Nokhodchi, A. (2006) The microsponge delivery system of benzoyl peroxide preparation, characterization and release studies. International Journal of Pharmaceutics, 308, 124-132. 

For samples with low values of K, < 500 ppm, the laser method, because of its small sample size, becomes more uncertain than a thermal release study with a larger sample size. It is not possible to compensate in the laser probe method by multiple pulses above MOO individual pulses which corresponds to evaporation of approximately 20 pg. It is conceivable that by completely redesigning a mass spectrometer with smaller volumes which is bakeable to higher temperatures to alleviate this problem. We have been able on occasion to work with samples as low as 100 ppm K but certainly not on a routine basis. 

Figure 2.18 Fourier transform infrared spectrum of sol-gel film composed of three layers and containing 10% vancomycin after 14 days of immersion in phosphate-buffered saline (weight measurements and release study showed 90% weight loss and 80% release). Intense silica bands and the bands associated with vancomycin (centred at 1660,1500 and 1397 cm-1) suggest the presence of a sol-gel film with vancomycin that remains after 14 days of immersion. (Reproduced from ref. 13, with permission.)...

H. S. Ch ng, in Formulation and Release Studies of 5-Fluorou-racil from Chitosan-Nanoparticles, Penang, Malaysia, 1999, Malaysian Society of Pharmacology and Physiology/Singapore University Press, p. S56. 

Interaction with such properties does, however, not allow the investigator to answer the question of where the drug is localized in the particles (on the surface or in the crystal lattice). Thermal interactions were also observed when an incorporated drug or a second type of triglyceride formed a separate phase within the nanoparticles [3,37,64,68]. Drug release studies can provide supportive information on the accessibility of the drug to the aqueous phase [72,108], but separation of the effects from the nanoparticles from those of additional colloidal structures — if present — may be difficult. 

Headspace analytical techniques, flavor release studies, 24,25/... 

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