This literature review is a compilation of the composition and, in most cases, the preparation instructions for simulated biological fluids that may be used as dissolution media in the evaluation of dissolution profiles and amount of drug released from pharmaceutical dosage forms. The use of simulated biological fluids can give a better understanding of the release mechanisms and possible in vivo behavior of a product and enhance the predictive capability of the dissolution testing. A summary of the major characteristics of the most used routes of administration that may affect dissolution and absorption of drug substances is presented. The routes and simulated biological fluids covered by this review are: • Parenteral: simulated body fluid and simulated synovial fluid. • Oral: fasted-state simulated gastric fluid, fed-state simulated gastric fluid, fasted-state simulated intestinal fluid, fed-state simulated intestinal fluid, simulated colonic fluid, fasted-state simulated colonic fluid, and fed-state simulated colonic fluid. • Buccal and sublingual: simulated saliva. • Pulmonary: simulated lung fluid. • Vaginal: simulated vaginal fluid and simulated semen. • Ophthalmic: simulated tears. Simulated sweat is also included. Some examples of how these simulated biological fluids are used to evaluate dosage forms are included in each route of administration. INTRODUCTION Until some decades ago, most of the conventional pharmaceutical dosage forms were essentially injections, oral formulations (solutions, suspensions, tablets, and capsules), topical creams, and ointments. With the progress of drug delivery technology, novel dosage forms have been developed to overcome the problems associated with conventional drug delivery. Research has been directed toward the use of alternatives to the parenteral route for drugs that cannot be delivered orally. Potential alternative portals of drug entry to the systemic circulation include buccal, sublingual, nasal, pulmonary, and vaginal routes, among others. These routes of administration are also used for the local delivery of drugs directly to the site of action, with consequent reduction in the dose needed to produce a pharmacological effect, eliminating problems related to first-pass metabolism and possibly minimizing systemic side effects (1). An important application of dissolution testing is the prediction of in vivo performance of pharmaceutical dosage forms. The media typically used for quality control dissolution testing do not represent all aspects of the physiological conditions of the most used routes of administration and do not allow correlation with in vivo data. Prediction of dosage form performance in the site where most of the absorption occurs requires adequate simulation of the in vivo conditions. This paper describes some characteristics of the parenteral, oral, buccal and sublingual, pulmonary, ophthalmic, and vaginal routes that are important to consider when developing simulated media. A compilation of the composition and preparation of several simulated biological fluids, including simulated sweat, with potential use as dissolution media is presented. PARENTERAL ROUTE The most used routes of injection are intramuscular, intravenous, and subcutaneous and are normally associated with short-term effects. Novel implant devices that can adequately control drug release and provide a prolonged duration of effect have been developed (1). To evaluate the in vitro drug release from these dosage forms, the dissolution medium should have ion concentrations almost equal to those of the human plasma. Table 1 describes the ionic composition of simulated body fluid (SBF) and human blood plasma. Simulated body fluid was developed initially to evaluate the surface structural changes of glass-ceramics used to manufacture artificial vertebrae, ileum, tooth roots (2), and bioactive material used to repair hard tissues such as artificial middle-ear bone and maxillofacial implants (3). This simulated body fluid was prepared using the reagents listed in Table 2. These reagents were added to 700 mL of water in the order given in Table 2, one by one, after each reagent was completely dissolved. The pH was adjusted to 7.4 with 1 M *Corresponding author. diss-18-03-03.indd 15 8/31/2011 3:22:15 PM dx.doi.org/10.14227/DT180311P15

/pdf/simulated-biological-fluids-with-possible-application-in-3bqpblowoq.pdf

Simulated Biological Fluids with Possible Application in Dissolution Testing

Large production volumes of zinc oxide nanoparticles (ZnONP) might be anticipated to pose risks, of accidental inhalation in occupational and even in consumer settings. Herein, we further investigated the pathological changes induced by ZnONP and their possible mechanism of action. Two doses of ZnONP (50 and 150 cm2/rat) were intratracheally instilled into the lungs of rats with assessments made at 24 h, 1 wk, and 4 wks after instillation to evaluate dose- and time-course responses. Assessments included bronchoalveolar lavage (BAL) fluid analysis, histological analysis, transmission electron microscopy, and IgE and IgA measurement in the serum and BAL fluid. To evaluate the mechanism, alternative ZnONP, ZnONP-free bronchoalveolar lavage exudate, and dissolved Zn2+ (92.5 μg/rat) were also instilled to rats. Acridine orange staining was utilized in macrophages in culture to evaluate the lysosomal membrane destabilization by NP. ZnONP induced eosinophilia, proliferation of airway epithelial cells, goblet cell hyperplasia, and pulmonary fibrosis. Bronchocentric interstitial pulmonary fibrosis at the chronic phase was associated with increased myofibroblast accumulation and transforming growth factor-β positivity. Serum IgE levels were up-regulated by ZnONP along with the eosinophilia whilst serum IgA levels were down-regulated by ZnONP. ZnONP are rapidly dissolved under acidic conditions (pH 4.5) whilst they remained intact around neutrality (pH 7.4). The instillation of dissolved Zn2+ into rat lungs showed similar pathologies (eg., eosinophilia, bronchocentric interstitial fibrosis) as were elicited by ZnONP. Lysosomal stability was decreased and cell death resulted following treatment of macrophages with ZnONP in vitro. We hypothesise that rapid, pH-dependent dissolution of ZnONP inside of phagosomes is the main cause of ZnONP-induced diverse progressive severe lung injuries.

/pdf/progressive-severe-lung-injury-by-zinc-oxide-nanoparticles-1tr173rmhh.pdf

Progressive severe lung injury by zinc oxide nanoparticles; the role of Zn2+ dissolution inside lysosomes

Nanoparticles, the building blocks of many engineered nanomaterials, can make their way into the environment or into organisms, either accidentally or purposefully. The intent of this study is to provide some insight into the complex environmental, health, and safety issues associated with engineered nanomaterials. In particular, here the state of commercially manufactured silver nanoparticles—i.e., will silver nanoparticles be present as isolated particles, agglomerates, or dissolved ions—in two simulated biological media is explored. Two different commercially manufactured silver nanoparticle samples, one that has been surface modified with a thick polymer coating to render them more water-soluble and the other, with a sub-nanometer surface layer, are studied. The experimental results and the extended DLVO model calculations show that silver nanoparticles have a propensity to settle out in high ionic strength media independent of surface modification. Furthermore, single nanoparticles as well as aggregates/agglomerates are present together in these solutions. Silver ion release in these simulated biological buffers with pHs of 4.5 and 7.4 is negligible after 96 h.

Silver nanoparticles in simulated biological media: a study of aggregation, sedimentation, and dissolution

Zeta potential and solubility to toxic ions as mechanisms of lung inflammation caused by metal/metal-oxide nanoparticles

A critical review of approaches and limitations of inhalation bioavailability and bioaccessibility of metal(loid)s from ambient particulate matter or dust.

Simulants of lung interstitial fluid.

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Simulants of lung interstitial fluid.