In vitro permeation study of a mucoadhesive drug delivery system for controlled delivery of nonoxynol-9

Preparation and evaluation of an oral mucoadhesive gel containing nystatin-loaded alginate microparticles

Nystatin is an antifungal agent used for prophylaxis and treatment of candidiasis, especially oral mycosis. Efficacy of nystatin conventional dosage forms is limited by the short residence time and bitter taste of the drug. This research aims at designing an optimized formulation of oral mucoadhesive gel of nystatin-loaded alginate microparticles, which can be retained in the mouth. Sodium alginate solution containing nystatin was added to the solution of calcium chloride under stirring. Microparticles containing nystatin were incorporated into the Carbopol gel. Size, loading, and release profile and mucoadhesion were investigated. The most suitable microparticles with particle size of < 250 μm were prepared with alginate concentration of 1%(w/v), calcium chloride of 1%(w/v), drug:polymer concentration 1%, and ratio of alginate solution:calcium chloride of 1:10. This formulation showed 49.1% drug loading and 98.2% encapsulation efficiency. Carbopol 934 gel provided optimal mucoadhesive properties. Release profile proved a burst release, which can be attributed to the surface associated drug, followed by a slower sustained release phase for all microparticles. The developed system with ability to adhere to the oral mucosa has great appeal for treatment of localized infections and can mask bitter taste of the drug and be retained in the mouth for long periods.

Studies and methodologies on vaginal drug permeation

The vagina stands as an important alternative to the oral route for those systemic drugs that are poorly absorbed orally or are rapidly metabolized by the liver. Drug permeation through the vaginal tissue can be estimated by using in vitro, ex vivo and in vivo models. The latter ones, although more realistic, assume ethical and biological limitations due to animal handling. Therefore, in vitro and ex vivo models have been developed to predict drug absorption through the vagina while allowing for simultaneous toxicity and pathogenesis studies. This review focuses on available methodologies to study vaginal drug permeation discussing their advantages and drawbacks. The technical complexity, costs and the ethical issues of an available model, along with its accuracy and reproducibility will determine if it is valid and applicable. Therefore every model shall be evaluated, validated and standardized in order to allow for extrapolations and results presumption, and so improving vaginal drug research and stressing its benefits.

Spermicidal and antifertility effects of an imbibing and soluble nonoxynol-9 diaphragm (ISND) in rabbits

OBJECTIVE

To determine the minimum effective concentration (MEC) of an imbibing and soluble nonoxynol-9 (N-9) diaphragm (ISND) required for immobilisation of all spermatozoa in vitro and in vivo. The speed of semen absorbance, time of ISND to dissolution, and the antifertility effects were also investigated in rabbits.

METHODS

In vitro spermicidal tests with ISND were conducted using fresh semen from humans and rabbits. Spermicidal and antifertility effects were observed in vivo after the ISND was placed directly into the vagina of rabbits.

RESULTS

The MEC of N-9 required in the ISND to totally immobilise sperm within 20 seconds was 0.15 mg/ml for human sperm, and 0.5 mg/ml for rabbit sperm. The human semen was absorbed into the ISND in 45 minutes; the diaphragm dissolved in the vagina 3.5 hours later. In vivo, in rabbits, the MEC of N-9 required to immobilise sperm within five minutes of mating was 1 mg/kg in the ISND, and 10 mg/kg for the nonoxynol-9 film. The median effective dose of N-9 in the ISND was 1.07 mg/kg, whereas for the film it was 3.30 mg/kg.

CONCLUSION

The spermicidal and antifertility activities of a low dose N-9 in the ISND were high, with properties of imbibition and solubility confirmed.

The vagina as a route for drug delivery: a review

Overactive bladder (OAB) syndrome has a significant deleterious impact on quality of life. After conservative therapy and bladder retaining, antimuscarinic drugs remain the mainstay of OAB management. Oral therapy is associated with frequent side effects, leading to the development of alternative agents and formulations or the use of novel routes of drug administration, such as the vaginal route. The vagina is often ideal for drug delivery because it allows the use of lower doses, maintains steady drug administration levels, and requires less frequent administration than the oral route. With vaginal drug administration, absorption is unaffected by gastrointestinal disturbances, there is no first-pass effect, and use is discreet. The aim of this review is to provide a background overview of vaginal development, anatomy, and physiology and the effect this has on the use of this route for both local and systemic drug delivery, with special reference to OAB management. Vaginal therapy continues to be an underused route of drug delivery. Vaginal administration allows nondaily, low, continuous dosing, which results in stable drug levels and may, in turn, achieve a lower incidence of side effects and improve patient compliance. These benefits must be balanced against inherent patient or physician bias against using this route and the need to overcome cultural, personal, and hygiene-related barriers to this form of therapy. More sophisticated and programmable vaginal rings are being developed for systemic delivery of therapeutically important macromolecules, such as antimuscarinic therapy in OAB management.

Molecular optical imaging of therapeutic targets of cancer

Recent progress in discerning the molecular events that accompany carcinogenesis has led to development of new cancer therapies directly targeted against the molecular changes of neoplasia. Molecular-targeted therapeutics have shown significant improvements in response rates and decreased toxicity as compared to conventional cytotoxic therapies which lack specificity for tumor cells. In order to fully explore the potential of molecular-targeted therapy, a new set of tools is required to dynamically and quantitatively image and monitor the heterogeneous molecular profiles of tumors in vivo. Currently, molecular markers can only be visualized in vitro using complex immunohistochemical staining protocols. In this chapter, we discuss emerging optical tools to image in vivo a molecular profile of risk-based hallmarks of cancer for selecting and monitoring therapy. We present the combination of optically active, targeted nanoparticles for molecular imaging with advances in minimally invasive optical imaging systems, which can be used to dynamically image both a molecular and phenotypic profile of risk and to monitor changes in this profile during therapy.

Porcine vaginal mucosa as an in vitro permeability model for human vaginal mucosa

The availability of human tissue for experimental purposes is often problematical and use is thus made of animal tissue as models of the human tissue. In this study, porcine vaginal mucosa was used as an in vitro permeability model for human vaginal mucosa using tritium-labelled permeants (17beta-estradiol, r-arecoline, vasopressin, oxytocin and water). Fresh porcine and human vaginal tissues were frozen in liquid nitrogen and stored at -85 degrees C. In vitro permeability studies were performed using a flow-through diffusion apparatus (24 h, 20 degrees C, 1.5 ml/h). The mean steady state flux values for water, r-arecoline and vasopressin were approximately 4, 12 and 5% lower, while those for 17beta-estradiol and oxytocin were approximately 17 and 53% higher, through porcine vaginal mucosa as compared to human vaginal mucosa, respectively. Using a F-test (comparing whole curves), statistically significant differences in the diffusion of 17beta-estradiol, r-arecoline and oxytocin were indicated when comparing human and porcine vaginal mucosa. Generally, porcine vaginal mucosa seems a good in vitro permeability model for human vaginal mucosa. However, permeability of these two mucosa towards all permeants tested does not always correspond closely. These differences must always be considered when using porcine tissue as an in vitro permeability model for human vaginal mucosa.

Permeability of tritiated water through human cervical and vaginal tissue

The increased incidence of human immunodeficiency virus infection in women has identified an urgent need to develop a female-controlled method to prevent acquisition of human immunodeficiency virus and other sexually transmitted diseases. Women would apply the product intravaginally before intercourse. Development of such a product requires a better understanding of the permeability characteristics of the tissues with which such products would come into contact. However, limited studies have been performed in this area. In the present study, water permeability of fresh human cervical and vaginal tissue was evaluated. The average apparent permeability coefficient was found to be 8 x 10(-5) cm/s for fresh human cervical tissue and 7 x 10(-5) cm/s for fresh human vaginal tissue. Considering the lack of regularity in obtaining cervical and vaginal tissue from surgical specimens, additional tests were performed to evaluate the effect of freezing on tritiated water permeability. No statistically significant differences were observed in the permeability values obtained when comparing fresh versus frozen tissues.

The vagina as a route for systemic drug delivery

Exhaustive efforts have been made toward the administration of drugs, via alternative routes, that are poorly absorbed after the oral administration. The vagina as a route of drug delivery has been known since ancient times. In recent years, the vaginal route has been rediscovered as a potential route for systemic delivery of peptides and other therapeutically important macromolecules. However, successful delivery of drugs through the vagina remains a challenge, primarily due to the poor absorption across the vaginal epithelium. The rate and extent of drug absorption after intravaginal administration may vary depending on formulation factors, vaginal physiology, age of the patient and menstrual cycle. Suppositories, creams, gels, tablets and vaginal rings are commonly used vaginal drug delivery systems. The purpose of this communication is to provide the reader with a summary of advances made in the field of vaginal drug delivery. This report, therefore, summarizes various vaginal drug delivery systems with an introduction to vaginal physiology and factors affecting drug absorption from the vaginal route.

Insoluble ionic complexes of polyacrylic acid with a cationic drug for use as a mucoadhesive, ophthalmic drug delivery system

We have developed a new mucoadhesive drug delivery formulation based on an ionic complex of partially neutralized poly(acrylic acid) (PAA) and a highly potent beta blocker drug, levobetaxolol x hydrochloride (LB x HCl), for use in the treatment of glaucoma. PAA was neutralized with sodium hydroxide to varying degrees of neutralization. Aqueous solutions containing concentrations of LB x HCl equivalent to the degree of PAA neutralization were added to the PAA solutions and formed insoluble complexes, which were isolated. The complex formation was followed by turbidimetric titration, and the complexes were characterized by IR and 1H NMR spectroscopy. Complexes were prepared with varying degrees of drug loading, such that the same PAA chain would have free -COOH groups for mucoadhesion along with ionic complexes of LB x H+ with COO- groups. Thin films of the complexes dissociated to release the drug by ion exchange with synthetic tear fluid. The films shrunk continuously during release of the drug and dissolved completely in 1 h. Solid inserts of these films could be useful as a mucoadhesive ophthalmic drug delivery system.