Nasal administration of an ACTH(4-9) peptide analogue with dimethyl-beta-cyclodextrin as an absorption enhancer: pharmacokinetics and dynamics

Advancements in cyclodextrin-based controlled drug delivery: Insights into pharmacokinetic and pharmacodynamic profiles

This article discusses and summarizes some fascinating outcomes and applications of cyclodextrins (CDs) and their derivatives in drug delivery. These applications include the administration of protein, peptide medications, and gene delivery. Several innovative drug delivery systems, including NPs, microspheres, microcapsules, and liposomes, are designed with the help of CD, which is highlighted in this article. The use of these compounds as excipients in medicine formulation is reviewed, in addition to their well-known effects on drug solubility and dissolution, as well as their bioavailability, safety, and stability. Furthermore, the article focuses on many factors that influence the development of inclusion complexes, as having this information is necessary to manage these diverse materials effectively. An overview of the commercial availability, regulatory status, and patent status of CDs for pharmaceutical formulation is also presented. Due to the fact that CDs can discover new uses in drug delivery consistently, it is predicted that they will solve a wide range of issues related to the distribution of a variety of unique medications through various delivery channels.

Chemistry and engineering of cyclodextrins for molecular imaging

Cyclodextrins (CDs) are naturally occurring cyclic oligosaccharides bearing a basket-shaped topology with an "inner-outer" amphiphilic character. The abundance of hydroxyl groups enables CDs to be functionalized with multiple targeting ligands and imaging elements. The imaging time, and the payload of different imaging elements, can be tuned by taking advantage of the commercial availability of CDs with different sizes of the cavity. This review aims to offer an outlook of the chemistry and engineering of CDs for the development of molecular probes. Complexation thermodynamics of CDs, and the corresponding implications for probe design, are also presented with examples demonstrating the structural and physiochemical roles played by CDs in the full ambit of molecular imaging. We hope that this review not only offers a synopsis of the current development of CD-based molecular probes, but can also facilitate translation of the incremental advancements from the laboratory to real biomedical applications by illuminating opportunities and challenges for future research.

Cell transfection with a β-cyclodextrin-PEI-propane-1,2,3-triol nanopolymer

Successful gene therapy necessitates safe and efficient gene transfer. This article describes the use of a cationic polymer, which was synthesized by cross-linking low molecular weight branched poly(ethylenimine) (PEI) with both β-cyclodextrin and propane-1,2,3-triol, for efficient and safe non-viral gene delivery. Experimentation demonstrated that the polymer had a pH buffering capacity and DNA condensing ability comparable to those of PEI 25 kDa. In B16-F0 cells, the polymer increased the transfection efficiency of naked DNA by 700-fold and yielded better transfection efficiencies than Fugene HD (threefold higher) and PEI 25 kDa (fivefold higher). The high transfection efficiency of the polymer was not affected by the presence of serum during transfection. In addition to B16-F0 cells, the polymer enabled efficient transfection of HepG2 and U87 cells with low cytotoxicity. Our results indicated that our polymer is a safe and efficient transfection reagent that warrants further development for in vitro, in vivo and clinical applications.

Cyclodextrins in non-viral gene delivery

Cyclodextrins (CDs) are naturally occurring cyclic oligosaccharides. They consist of (α-1,4)-linked glucose units, and possess a basket-shaped topology with an "inner-outer" amphiphilic character. Over the years, substantial efforts have been undertaken to investigate the possible use of CDs in drug delivery and controlled drug release, yet the potential of CDs in gene delivery has received comparatively less discussion in the literature. In this article, we will first discuss the properties of CDs for gene delivery, followed by a synopsis of the use of CDs in development and modification of non-viral gene carriers. Finally, areas that are noteworthy in CD-based gene delivery will be highlighted for future research. Due to the application prospects of CDs, it is anticipated that CDs will continue to emerge as an important tool for vector development, and will play significant roles in facilitating non-viral gene delivery in the forthcoming decades.

Capric acid and hydroxypropylmethylcellulose increase the immunogenicity of nasally administered peptide vaccines

Immunization by the nasal route is an established method for the induction of mucosal and systemic humoral and cell-mediated antigen-specific responses. However, the effectiveness of nasal immunization is often hampered by the need for increased doses of antigen. Bioadhesives and absorption enhancers were investigated for their ability to enhance immune responses in mice after nasal immunization with model HIV-1 peptide and protein immunogens. Two additives, hydroxypropylmethylcellulose (HPMC) and capric acid, consistently enhanced antigen-specific serum IgG endpoint titers under conditions in which antigen dose was limiting. Nasal immunization of mice with 20 microg of an HIV-1 peptide immunogen plus cholera toxin (CT) as adjuvant induced serum antipeptide IgG titers of 1:9.5log2 after four immunizations while the addition of CA or HPMC to the vaccine formulation increased serum antipeptide IgG titers to 1:15.4log2 and 1:17.6log2, respectively. When 5 microg recombinant HIV-1 gp41 was used as the immunogen, the addition of CA or HPMC to the vaccine formulation increased serum anti-gp41 IgG titers to 1:11.6log2 and 1:8.8log2, respectively, compared to 1:5.2log2 after three nasal immunizations with 5 microg gp41 + CT alone. Thus, HPMC and capric acid may be useful additives that increase the immunogenicity of nasally administered vaccines and permit less antigen to be used with each immunization.

Pharmacokinetic Advantage of an Intranasal Preparation of a Novel Anti-osteoporosis Drug, L-Asp-Hexapeptide-Conjugated Estradiol

We examined the usefulness of intranasal (i.n.) administration of a novel osteotropic prodrug of estradiol, estradiol-17beta-succinate-(L-aspartate)6 (E2.17D6), for selective drug delivery to bone. E2.17D6 alone or with 5% 2,6-di-O-methyl-beta-cyclodextrin (DMbetaCD), 5% beta-cyclodextrin (betaCD), or 10% hydroxypropyl cellulose (HPC) as an absorption enhancer was administered to ovariectomized (OVX) mice via the i.n. route. The oral and nasal bioavailability after p.o. or i.n. administration of E2.17D6 (3.7 micromol/kg) in mice amounted to 9.9 and 23.0% of the dose, respectively. The values of nasal bioavailability of E2.17D6 administered with DMbetaCD, betaCD, and HPC were 74.9, 55.8, and 49.1%, respectively. The plasma concentration of E2.17D6 after i.n. administration of E2.17D6-DMbetaCD decreased rapidly to the endogenous level by 6 h, but the concentration in the bone was about 200 times higher than that in plasma, and decreased slowly over a period of about a week. When E2 (total dose 4.4 micromol/kg, i.n., every 3rd day) was administered to OVX mice for 35 d, bone mineral density (BMD), liver weight, and uterus weight increased, whereas E2.17D6-DMbetaCD (total dose 0.44 to 8.8 micromol/kg, i.n., every 7th day) increased only BMD in a dose-dependent manner. In conclusion, intranasally administered E2.17D6-DMbetaCD has a potent antiosteoporotic effect without side effects, and has potential to provide an improved quality of life for patients with osteoporosis.

Cyclodextrin-Mediated Drug Release from Liposomes Dispersed Within a Bioadhesive Gel

PURPOSE

The aim of the present study was to design a new mucosal drug delivery system composed of liposomes dispersed within a bioadhesive hydrogel containing methyl-beta-cyclodextrin (Me(beta)CD) for controlled drug release.

METHODS

A hydrophilic model molecule, inulin, was encapsulated within positively charged and PEG-ylated liposomes and its release was measured in the presence of Me(beta)CD after vesicle dispersion within the bioadhesive Carbopol 974P gel. Freeze-fracture electron microscopy (FFEM) was used to follow liposome morphological changes when dispersed within the hydrogel. Liposome-Me(beta)CD interactions were investigated by turbidity monitoring during continuous addition of Me(beta)CD to liposomes and by FFEM.

RESULTS

Inulin diffusion within the gel was influenced by Carbopol 974P concentration since no gel erosion occurred. When dispersed within the gel, positively charged liposomes displayed a higher stability than PEG-ylated vesicles. In the presence of Me(beta)CD, higher amounts of free inulin were released from liposomes, especially in Carbopol-free system. Me(beta)CD appeared to diffuse towards lipid vesicles and permeabilized their bilayer allowing inulin leakage. Indeed, freeze-fracture experiments and liposome turbidity monitoring have shown that Me(beta)CD behaved as a detergent behavior, resulting in lipid vesicle solubilization.

CONCLUSION

is able to mediate, within a bioadhesive hydrogel, the release of a liposome-encapsulated molecule allowing further application of this delivery system for mucosal administration.

Absorption enhancers in pulmonary protein delivery

Extensive research efforts have been directed towards the systemic administration of therapeutic proteins and poorly absorbed macromolecules via various nontraditional, injection-free administration sites such as the lung. As a portal for noninvasive delivery, pulmonary administration possesses several attractive features including a large surface area for drug absorption. Nevertheless, achieving substantial bioavailability of proteins and macromolecules by this route has remained a challenge, chiefly due to poor absorption across the epithelium. The lungs are relatively impermeable to most drugs when formulated without an absorption enhancer/promoter. In an attempt to circumvent this problem, many novel absorption promoters have been tested for enhancing the systemic availability of drugs from the lungs. Various protease inhibitors, surfactants, lipids, polymers and agents from other classes have been tested for their efficacy in improving the systemic availability of protein and macromolecular drugs after pulmonary administration. The purpose of this article is to provide the reader with a summary of recent advances made in the field of pulmonary protein delivery utilizing absorption enhancers. This report reviews the various agents used to increase the bioavailability of these drugs from the lungs, their mechanisms of action and effectiveness, and their potential for toxicity.

Pharmacokinetic analysis of 6-monoamino-beta-cyclodextrin after intravenous or oral administration to rats using a specific enzyme immunoassay

We have developed a highly sensitive enzyme immunoassay for 6-monoamino-beta-CD (mono(6-amino-6-deoxy)cyclomaltoheptaose) and its parent compound (beta-CD) with a detection limit in the 100 pg/mL range. The polyclonal antibodies obtained are highly specific for the beta-cyclodextrin core and do not recognize other cyclic cyclodextrins (i.e., alpha- and gamma-CD) or linear analogues. This enzyme immunoassay can be used to quantify 6-monoamino-beta-CD in rat urine and plasma. Using this immunoassay, we have evaluated the main pharmacokinetic parameters of 6-monoamino-beta-CD after iv administration to the rat of a 25 mg/kg dose. Since this method is strictly specific to the native beta-CD form, we have demonstrated that the molecule rapidly disappeared from plasma but is probably distributed in the tissues. The urinary route appears as the predominant way of elimination since almost all the administered drug is recovered in urine. Finally, analysis of the same molecule after oral administration to the rat (25 mg/kg) demonstrates low plasma levels and that about 1% of the administered dose is excreted in urine. These experiments demonstrate the high stability of the beta-CD core irrespective of the method of administration. This immunological method could provide relevant information on the fate of beta-CD and some derivatives for drug delivery using different modes of administration (oral, parenteral, transmucosal, or dermal).

Efficacy, safety and mechanism of cyclodextrins as absorption enhancers in nasal delivery of peptide and protein drugs

Cyclodextrins are used in nasal drug delivery as absorption enhancing compounds to increase the intranasal bioavailability of peptide and protein drugs. The most effective cyclodextrins in animal experiments are the methylated derivatives, dimethyl-beta-cyclodextrin and randomly methylated beta-cyclodextrin, which are active at low concentrations ranging between 2% and 5%. However, large species differences between rats, rabbits and humans exist for the nasal absorption enhancement by cyclodextrins. Based on toxicological studies of the local effects of cyclodextrins on the nasal mucosa dimethyl-beta-cyclodextrin and randomly methylated beta-cyclodextrin are considered safe nasal absorption enhancers. Their effects were quite similar to controls (physiological saline), but smaller than those of the preservative benzalkonium chloride in histological and ciliary beat frequency studies. In these studies, and in a study of the release of marker compounds after nasal administration, methylated beta-cyclodextrins were less toxic than sodium glycocholate, sodium taurodihydrofusidate, laureth-9 and L-alpha-phosphatidylcholine. Systemic toxicity after nasal cyclodextrin administration is not expected, because very low doses of cyclodextrins are administered and only very small amounts are absorbed. The mechanism of action of cyclodextrins may be explained by their interaction with the nasal epithelial membranes and their ability to transiently open tight junctions.

Peptide hormones: Review of current and emerging uses by nasal delivery

The family of clinically available peptide hormones (PHs) is expanding in an exponential way, and advancement of knowledge of the basic mechanisms of action of PHs has led to multiplication of the possible clinical indications of already known PHs, and appears even more promising for still unknown PHs. A common obstacle to a full routine use of PHs is represented by the fact that PHs cannot be administered by the oral route, since they undergo digestion and inactivation in the gastrointestinal tract and a significant first pass metabolism in the liver. One alternative is represented by intranasal administration of PHs. The intranasal route of administration of PHs is also very attractive because of its convenience, which should assure a good compliance by patients. Luteinizing hormone releasing hormone, the analogues, desmopressin, oxytocin and salmon calcitonin are already marketed for intranasal administration; for salmon calcitonin, studies about bioavailability have been scanty in the past, but should be re-considered in order to fully explore its clinical benefit.Intranasal peptide hormones not yet on the market are insulin, glucagon, growth hormone releasing hormone (GHRH) and GHRP, GH and somatostatin, but the scenario is likely to change in a short period of time. Hexarelin seems very effective and is at a promising stage of development; also, glucagon appears mature enough to undergo extensive clinical evaluation and possibly marketing. The concern is why other peptides have not been further evaluated, as is the case for somatostatin and its analogues.

Pharmaceutical applications of cyclodextrins. 2. In vivo drug delivery

The objective of this Review is to summarize and critique recent findings and applications of both unmodified and modified cyclodextrins for in vivo drug delivery. This review focuses on the use of cyclodextrins for parenteral, oral, ophthalmic, and nasal drug delivery. Other routes including dermal, rectal, and pulmonary delivery are also briefly addressed. This Review primarily focuses on newer findings concerning cyclodextrin derivatives which are likely to receive regulatory acceptance due to improved aqueous solubility and safety profiles as compared to the unmodified cyclodextrins. Many of the applications reviewed involve the use of hydroxypropyl-beta-cyclodextrins (HP-beta-CDs) and sulfobutylether-beta-cyclodextrins (SBE-beta-CDs) which show promise of greater safety while maintaining the ability to form inclusion complexes. The advantages and limitations of HP-beta-CD, SBE-beta-CD, and other cyclodextrins are addressed.

Methylated beta-cyclodextrins are able to improve the nasal absorption of salmon calcitonin

The absorption enhancing effect of methylated beta-cyclodextrins on the nasal absorption of salmon calcitonin (sCT) was studied in rats and rabbits. The nasal absorption of sCT following administration without additives was low in both species. The absorption in rats could be largely improved by coadministration of cyclodextrins as apparent from the effect on serum calcium concentrations. Trimethyl-beta-cyclodextrin (TM beta CD), at a concentration of 5% (w/v), was the least potent enhancer. Randomly methylated-beta-cyclodextrin (RM beta CD) and dimethyl-beta-cyclodextrin (DM beta CD), all at a concentration of 5% (w/v), were almost equally effective in decreasing serum calcium levels, and the hypocalcemic responses were similar to those of i.v. and s.c. injected sCT. Absorption enhancement was already achieved with 1% DM beta CD added to the nasal formulations. In rabbits, only the effect of DM beta CD on the nasal sCT absorption was investigated. A total serum calcium decrement in 4 hours of 9.4 +/- 3.9% (mean +/- SD) was observed following nasal administration of 12.6 IU/kg sCT with 5% DM beta CD, comparable to that of i.v.-injected sCT. In conclusion, the methylated cyclodextrins DM beta CD and RM beta CD are suitable absorption enhancers for nasal sCT administration, which is expected to have a clinical impact on the therapy with calcitonin.

The effect of cyclodextrins on the stability of peptides in nasal enzymic systems

Leucine enkephalin (YGGFL) undergoes rapid degradation in sheep nasal mucosa to yield GGFL which is further degraded to FL. The activity of the nasal mucosal homogenate against YGGFL and GGFL (t1/2 12 and 7 min) was significantly greater than that observed with a nasal wash fluid (t1/2 40 and 13 min). The effect of cyclodextrins on the rate of degradation of FGG and YGGFL by leucine aminopeptidase (LAP) and of GGF by carboxypeptidase A (CPA) was monitored. Little effect was observed with FGG (with LAP) but the half-life of YGGFL (with LAP) was extended from approximately 44 min to approximately 75 min in the presence of a 25-fold excess of beta-cyclodextrin. The stability of GGF (with CPA) was also enhanced; an effect was observable with a 5-fold excess of cyclodextrin and the half-life could be extended by 40-75%. An equation is presented which allows the estimation of the concentration of free peptide in the peptide-cyclodextrin solutions.