Absorption and blood leukocyte dynamics of recombinant human granulocyte colony-stimulating factor (rhG-CSF) from intranasally administered preparations containing rhG-CSF and cyclodextrins in rabbits

Absorption enhancement of a protein drug by nitric oxide donor: effect on nasal absorption of human granulocyte colony-stimulating factor

The objective of this study was to evaluate the effect of a nitric oxide (NO) donor, S-nitroso-N-acetyl-DL-penicillamine (SNAP), on the nasal absorption of recombinant human granulocyte colony-stimulating factor (rhG-CSF) in rabbits and to evaluate the irritation (cytotoxicity) potential of the NO donor on the mucosal membrane using a cultured cell system (strain KB, human epidermoid carcinoma of the floor of the mouth). Significantly higher serum G-CSF concentration and increased total leukocyte count in the peripheral blood were observed after coadministration of rhG-CSF (100 microg/kg) with SNAP at various doses (0.3-3.3 mg/kg). The serum G-CSF concentration and the increased total leukocyte count were markedly decreased by the presence of the NO scavenger, 2-(4-carboxyphenyl)-4,4,5,5-tetramethyl-imidazole-1-oxyl 3-oxide sodium salt (carboxy-PTIO), in combination with rhG-CSF and SNAP. However, no significant inhibitory effect of glutathione (peroxynitrite scavenger) on the absorption-enhancing effect of SNAP was observed. These results suggest that carboxy-PTIO inhibits the absorption-enhancing effect of NO released from SNAP. We found that SNAP has a very low potential for cytotoxicity, as evaluated by the cell detachment assay, release of lactate dehydrogenase (LDH) from cultured cells and morphological observations of nasal tissue of rabbits. It is concluded that a NO donor such as SNAP is a promising absorption enhancer for nasal protein-drug delivery.

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.

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.

Pharmacokinetics and pharmacodynamics of recombinant human granulocyte colony-stimulating factor (rhG-CSF) following intranasal administration in rabbits

The objective of this study was to evaluate the pharmacokinetics and pharmacodynamics of G-CSF as well as their relationship following intranasal (i.n.) administration of aqueous rhG-CSF preparations with or without additives. In order to achieve a better understanding of the dosage regimen and the effectiveness of intranasally administered rhG-CSF in inducing leukopoiesis, we investigated rhG-CSF absorption and blood leukocyte dynamics with respect to dose in rabbits. RhG-CSF could be absorbed through the nasal cavity of rabbits when rhG-CSF aqueous preparations, especially those containing alpha-cyclodextrin (alpha-CyD) were intranasally administered. We found that serum G-CSF levels and the total count of leukocytes in peripheral blood (total blood leukocyte count) showed a dose-dependent increase with rhG-CSF. The area under the serum G-CSF concentration-time curve (AUC, a pharmacokinetic parameter) and the area under the increased total blood leukocyte count-time curve (AUL, a pharmacodynamic parameter) increased with increase of dose of rhG-CSF administered intranasally. Good agreement was observed between log AUC and AUL; thus, it is concluded that an increase of AUC leads to an increase in effectiveness of rhG-CSF in inducing leukopoiesis in rabbits. A novel rhG-CSF delivery system in the form of i.n. administration of rhG-CSF was thus achieved.