Semisolid formulations

The amounts of ointments and creams people apply are highly individualized. So are the techniques of application. Some patients vigorously rub semisolid formulations into the skin, while others just spread films until they are more or less uniform over the desired area. While pharmacokinetic assessments of a system s delivery attributes is ordinarily done using normal skin (in vitro) or on healthy volunteers (in vivo), the site of its clinical deployment is usually anything but normal. Rather, it is determined by the skin condition to be treated. Clearly, the manufacturer is without control over how a disease is expressed in a particular patient. For many diseases, disease manifestation can be anywhere on the body. Moreover, from individual to individual it varies in intensity and vastness. Thus, more area may be involved in one case than in another, and the barrier function of the skin may be more or less intact in any instance. This creates a set of imponderables with respect to delivery, efficacy, and safety. 

M DiBase, C Rhodes. Investigations of epidermal growth factor in semisolid formulations. Pharm Acta Helv 66 165, 1991. 

Solubility enhancement systems lipid-based systems, nanoparticles, surfactants, semisolid formulations... 

The solubilization of a drug substance in monophasic liquid crystalline vehicles gives semisolid formulations which are preferably used for topical application (see Surfactant Gels and Transdermal Patches above). 

RHH Neubert, Y Mrestani, M Schwarz, B Colin. Application of micellar electrokinetic chromatography for analyzing antiviral drugs in pharmaceutical semisolid formulations. J Pharm Biomed Anal 16 893-897, 1998. 

The presence and state of solid lipid nanoparticles incorporated into semisolid formulations have also been investigated by DSC [77,83,84]. Using this method, de Vringer and de Ronde were able to draw conclusions on the preparation-dependent distribution of the matrix lipid of their particles in the different phases of a cream formulation [77]. 

Oral liquid and semisolid formulations containing water as part of the vehicle may be prone to microbial spoilage in the absence of a preservative. In the case of pharmaceutical creams, these are usually oil-in-water emulsions stabilized using a surfactant. Phenolic preservatives, e.g., parabens esters, are inactivated in the presence of nonionic surfactants, and this detrimental interaction can have serious consequences for preservation of the product (20). 

Corbo, M.. T. W. Schultz. G. K. Wong, and G. A. Van Buskirk, Development and Validation of In Vitro Release Testing Methods for Semisolid Formulations, Pharmaceutical Technology 17(91 112-128. 1993. 

Neubert, R. Collin, B. 8t Wartewig, S., Direct determination of drug content in semisolid formulations using step-scan FT-IR photoacoustic spectroscopy Pharm. Res. 1997, 14, 946-948. 

A modified Franz diffusion cell has been developed in our laboratory in order to simultaneously measure the amount of drug released by diffusion from a semisolid formulation and the amount of drug washed away by a fluid stream simulating the removal action exerted by... 

The efficient extraction of analytes adsorbed or absorbed as in creams, ointments, and other semisolid formulations are difficult to achieve. For adsorbed analytes, displacement from the adsorption sites by a small amount of acid, base, or buffer is effective. For semisolid formulations, solvent extraction is generally performed at elevated temperatures so as to melt the solid and increase the extraction efficiency. 

In Vivo Bioequivalence Studies In vivo studies are conducted to establish the biological availability or activity of the drug from a topically applied semisolid formulation. Dermatopharmacokinetic studies, pharmacodynamic studies, or comparative clinical trials are generally conducted to assess the bioequivalence of topical products [16,17]. 

PH electrodes from Crison, combination electrodes that contain a built-in temperature probe, a bridge electrolyte chamber and movable sleeve junction from Mettler, and combination pH puncture electrodes with spear-shaped tip from Mettler are some commercially available pH measurement systems for semisolid formulations. 

Capsules, particularly soft capsules, have been used as vaginal drug delivery systems, but with modest popularity. These systems are relatively stable, particularly when compared with semisolid formulations or vaginal suppositories, being an adequate way to deliver liquid drugs within a solid dosage form. 

Semisolid formulations are often used as contraceptives, particularly gels. These drug delivery systems were demonstrated to be useful, namely in reducing the toxicity of nonoxynol-9 [295], Adequate formulation of these products has also been... 

Jones, D. S., Irwin, C. R., Woolfson, A. D., Djokic, J., and Adams, V. (1999), Physicochemical characterization and preliminary in vivo efficacy of bioadhesive, semisolid formulations containing flurbiprofen for the treatment of gingivitis, J. Pharm. Sci., 88, 592-598. 

Automatic-filling machines are available, which can have more than one product-dosing device. Therefore, combinations of materials can be filled into the same capsule, such as mixture of a powder and a semisolid formulation or a powder and a tablet. The same formulation rules apply as to single forms. Combinations of materials allow the formulator to achieve specific goals in terms of product stability and types of release. 

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