Drugs Incorporation

Hair cortex protects hair from removal or incoiporatioii of drugs by the external environment 

Entrapment model of drug incorporation. Drugs are incorporated into hair from the bloodstream during the growth phase. Their concentration in the hair reflects that present in the bloodstream. A central dogma of the entrapment model is that hair is resistant to incorporation of drugs from outside contamination. 

Can Exogenously Applied Drugs be Incorporated into the Hair Matrix  

See the section entitled Can Externally Applied Drugs be Removed  

Drugs in the external environment are readily incorporated and indisdngui ble from drugs in vivo 

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Drug incorporation was also influenced by stabilization temperature for different reasons. Low incorporation was noted at high tempera-... 

Drug incorporating a device component with the combination product having the primary intended purpose of fulfilling a drug function. 

Drug incorporation increases with type 1 and type 11 NLC because of a reduced or lacking crystalhnity, whereas drugs dissolve in oily nanocompartments located in the sohd matrix of type HI particles. The distinct advantage of NLC compared with SLN should be the higher drug loading capacity. 

Therefore, extensive characterization is required, as the physicochemical properties of lipid nanodispersions influence not only drug incorporation and release but also the physical stability of the preparation for example, drug localization in the matrix. Several methods have to be combined for characterization to allow detection of dynamic processes such as changes in lipid modifications, particle aggregation, and the formation of nanostructures of other kinds. 

In addition to particle size, the degree of crystallinity and the modification of the lipid are of relevance for drug incorporation and release. Lipid crystallization and a change of the modification can be delayed with very small particles and in the presence of emulsifiers [20,21]. 

FIGURE 7.3 Models of drug incorporation into solid lipid nanoparticles. 

Solidification of the particles may not be the final step in the formation process of solid lipid particles. Lipidic materials exhibit rich polymorphism [69,70], which may also occur in the dispersed state. In nanoparticles, the polymorphic behavior of the matrix lipids may, however, differ distinctly from that in the bulk material. Polymorphic transitions are usually accelerated in the nanoparticles compared with the bulk lipids [2,62]. In some cases, polymorphic forms not observable in the corresponding bulk materials were detected in lipid nanoparticles [1,65]. Because polymorphism can affect pharmaceutically relevant properties of the particles, such as the drug incorporation capacity [65], corresponding investigations should also be included in the characterization process. As long as polymorphic or other crystalaging phenomena have not terminated, the particle matrix cannot be regarded as static, and alterations of the particle properties may still occur. 

Any conclusions about the organization of different components within the dispersions should take the ultrastructure of the systems into consideration. The surface-active agents that act as stabilizers for the nanoparticles are often able to form additional colloidal structures, such as vesicles or micelles, by self assembly. In addition to a potential importance in the formation and stability of the dispersions, such structures contain lipophilic domains that may represent alternative compartments for the localization of incorporated drugs. As a consequence, their presence may affect drug incorporation and release. 

Schwarz C. and Mehnert W., Solid lipid nanoparticles (SEN) for controlled drug delivery. 11. Drug incorporation and physicochemical characterization, J. Microencapsulation, 16, 205, 1999. 

Therefore, an economic analysis must measure the quality of life of the patient to ensure that the value of the drug incorporates the patient s perspective. Quality of life is a concept that usually incorporates the physical, mental and social well-being of the patient. Initial doubts concerning the ability of schizophrenic patients to provide reliable and valid reports of their own quality of life led to the use of proxies for patient interviews. Caregivers and clinicians were consulted most often. However, recent research has shown that the use of proxies can produce very different results to those derived directly from the patient s responses. In addition, research now indicates that schizophrenic patients are able to provide stable, reliable and valid self-reports of their psychological well-being, health status and subjective evaluation of drug therapies (Awad et al., 1995). 

Optical microscopy and scanning electron microscopy (SEM) were used to evaluate the drug incorporation and surface shape of the microspheres prepared under the various conditions. Particle size was determined using a Tiyoda microscope. Samples of microspheres (180-200) were dispersed on a slide and their diameter was then sized using suitable objectives. 

Differential thermal analysis (heating cycles of 90-200°C) of the pure nifedipine, empty Eudragit microspheres and microspheres containing various amounts of nifedipine was carried out to evaluate the internal structure alter drug incorporation. 

J.C.Fu, A.K.Kale, and D.L.Moyer, Drug-incorporated silicone discs as sustained release capsules. I.Chloroquione diphosphate, / Biomed. Mater. Res., 7, 79-93 (1973). 

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