Comprehensive evaluation of microneedle-based intradermal adalimumab delivery vs. subcutaneous administration: results of a randomized controlled clinical trial

AIMS

To evaluate feasibility of intradermal (i.d.) adalimumab administration using hollow microneedles, and to compare a single i.d. dose of adalimumab using a hollow microneedle with a single subcutaneous (s.c.) dose using a conventional needle.

METHODS

In this single-centre double-blind, placebo-controlled, double-dummy clinical trial in 24 healthy adults we compared 40 mg adalimumab (0.4 mL) administered i.d. using a hollow microneedle with a s.c. dose using a conventional needle. Primary parameters were pain, acceptability and local tolerability; secondary parameters safety, pharmacokinetics and immunogenicity. We explored usability of optical coherence tomography, clinical photography, thermal imaging, and laser speckle contrast imaging to evaluate skin reaction after i.d. injections. In vitro protein analysis was performed to assess compatibility of adalimumab with the hollow microneedle device.

RESULTS

While feasible and safe, injection pain of i.d. adalimumab was higher compared to s.c. adalimumab (35.4 vs. 7.9 on a 100-point visual analogue scale). Initial absorption rate and relative bioavailability were higher after i.d. adalimumab (time to maximum plasma concentration = 95 h [47-120]; Frel = 129% [6.46%]) compared to s.c. adalimumab (time to maximum plasma concentration = 120 h [96-221]). Anti-adalimumab antibodies were detected in 50% and 83% of the subjects after i.d. and s.c. adalimumab, respectively. We observed statistically significantly more erythema and skin perfusion after i.d. adalimumab, compared to s.c. adalimumab and placebo injections (P < .0001). Cytokine secretion after whole blood lipopolysaccharide challenge was comparable between administration routes.

CONCLUSIONS

Intradermal injection of adalimumab using hollowing microneedles was perceived as more painful and less accepted than s.c. administration, but yields a higher relative bioavailability with similar safety and pharmacodynamic effects.

Hydroxocobalamin Uptake into the Cerebrospinal Fluid after Nasal and Intravenous Delivery in Rats and Humans

The possibility of direct transport of hydroxocobalamin from the nasal cavity into the cerebrospinal fluid (CSF) after nasal administration in rats was investigated and the results were compared with a human study. Hydroxocobalamin was given to rats (n=8) both intranasally (214 microg/rat) and intravenously (49.5 microg/rat) into the jugular vein using a Vascular Access Port (VAP). Prior to and after drug administration, blood and CSF samples were taken and analysed by radioimmunoassay. The AUCCSF/AUCplasma ratio after nasal delivery does not differ from the ratio after intravenous infusion, indicating that hydroxocobalamin enters the CSF via the blood circulation across the blood-brain barrier (BBB). This same transport route is confirmed by the cumulative AUC-time profiles in CSF and plasma, demonstrating a 30 min delay between plasma absorption and CSF uptake of hydroxocobalamin in rats and in a comparative human study. The present results in rats show that there is no additional uptake of hydroxocobalamin in the CSF after nasal delivery compared to intravenous administration, which is in accordance with the results found in humans. This indicates a predictive value of the used rat model for the human situation when studying the nose to CSF transport of drugs.

Water Distribution and Natural Moisturizer Factor Content in Human Skin Equivalents Are Regulated by Environmental Relative Humidity

Human skin equivalents (HSEs) show great similarities to human native skin. However, one of the key processes impaired under in vitro conditions is desquamation. Desquamation involves the degradation of the corneodesmosomes, in which various enzymes participate. Activation of these enzymes is affected by several microenvironmental factors such as pH and water level. The water level is assumed to depend on the presence of natural moisturizing factors (NMF). In this study, the levels of water and one of the prominent NMF components--pyrrolidone carboxylic acid (PCA)--were examined. In HSE generated under normal culture conditions (93% relative humidity (RH)), the water level and PCA content appeared to be much lower than in the native counterpart. To increase the water and PCA levels in HSE, a culture method was established in which HSE was reconstructed under reduced RH. Although at 40% RH the PCA levels in reconstructed and native tissue are similar, the hydration levels in reconstructed tissue remain still lower. Only topical application of water induced marked swelling of corneocytes. This clearly shows that the stratum corneum water level in HSE is regulated by other, still unknown, factors, in addition to NMF.

N-Trimethyl chitosan (TMC) nanoparticles loaded with influenza subunit antigen for intranasal vaccination: Biological properties and immunogenicity in a mouse model

In this study, the potential of N-trimethyl chitosan (TMC) nanoparticles as a carrier system for the nasal delivery of a monovalent influenza subunit vaccine was investigated. The antigen-loaded nanoparticles were prepared by mixing a solution containing TMC and monovalent influenza A subunit H3N2 with a tripolyphosphate (TPP) solution, at ambient temperature and pH 7.4 while stirring. The nanoparticles had an average size of about 800 nm with a narrow size distribution and a positive surface charge. The nanoparticles showed a loading efficiency of 78% and a loading capacity of 13% (w/w). It was shown that more than 75% of the protein remained associated with the TMC nanoparticles upon incubation of the particles in PBS for 3h. The molecular weight and antigenicity of the entrapped hemagglutinin was maintained as shown by polyacrylamide gel electrophoresis and Western blotting, respectively. Single i.n. or i.m. immunization with antigen-loaded TMC nanoparticles resulted in strong hemagglutination inhibition and total IgG responses. These responses were significantly higher than those achieved after i.m. administration of the subunit antigen, whereas the IgG1/IgG2a profile did not change substantially. The i.n. administered antigen-TMC nanoparticles induced higher immune responses compared to the other i.n. antigen formulations, and these responses were enhanced by i.n. booster vaccinations. Moreover, among the tested formulations only i.n. administered antigen-containing TMC nanoparticles induced significant IgA levels in nasal washes of all mice. In conclusion, these findings demonstrate that TMC nanoparticles are a potent new delivery system for i.n. administered influenza antigens.

Pharmacokinetics and pharmacodynamics analysis of transdermal iontophoresis of 5-OH-DPAT in rats: in vitro-in vivo correlation

Pharmacokinetics and dopaminergic effect of dopamine agonist 5-OH-DPAT in vivo were determined following transdermal iontophoresis in rats based on drug concentration in plasma (C(p)) and dopamine levels in striatum (C(DA)). Correlation of the in vitro transport with the pharmacokinetic-pharmacodynamic (PK-PD) profiles was characterized in the transport in dermatomed rat skin (DRS) and rat stratum corneum (RSC). The integrated in vivo PK-PD and in vitro transport models successfully described time course of C(p), C(DA), and in vitro flux in DRS and RSC. Population value of steady-state flux (J(ss)) in vivo (31 nmol/cm(2) . h with 95% confidence interval (CI) = 20-41) is closer to J(ss) in vitro in DRS (61 nmol/cm(2) . h, CI = 54-67) than in vitro J(ss) in RSC (98 nmol/cm(2) . h, CI = 79-117). On the other hand, skin release rate constant (K(R)) in vivo was similar to the K(R) in RSC (4.8/h, CI = 2.4-7.1 vs. 2.6/h, CI = 2.5-2.6). Kinetic lag time (t(L)) in vivo was negligible, which is close to in vitro t(L) in RSC (0.0 h, CI = 0.0-0.1). Based on nonlinear mixed-effect modeling, profiles of C(p) and C(DA) were successfully predicted using in vitro values of J(ss) in DRS with K(R) and t(L) in RSC. A considerable dopaminergic effect was achieved, indicating the feasibility to reach therapeutically effective concentrations of 5-OH-DPAT upon transdermal iontophoresis.

Preparation and characterization of protein-loaded N-trimethyl chitosan nanoparticles as nasal delivery system

In this study, the potential of N-trimethyl chitosan (TMC) nanoparticles as a carrier system for the nasal delivery of proteins was investigated. TMC nanoparticles were prepared by ionic crosslinking of TMC solution (with or without ovalbumin) with tripolyphosphate, at ambient temperature while stirring. The size, zeta-potential and morphology of the nanoparticles were investigated as a function of the preparation conditions. Protein loading, protein integrity and protein release were studied. The toxicity of the TMC nanoparticles was tested by ciliary beat frequency measurements of chicken embryo trachea and in vitro cytotoxicity assays. The in vivo uptake of FITC-albumin-loaded TMC nanoparticles by nasal epithelia tissue in rats was studied by confocal laser scanning microscopy. The nanoparticles had an average size of about 350 nm and a positive zeta-potential. They showed a loading efficiency up to 95% and a loading capacity up to 50% (w/w). The integrity of the entrapped ovalbumin was preserved. Release studies showed that more than 70% of the protein remained associated with the TMC nanoparticles for at least 3 h on incubation in PBS (pH 7.4) at 37 degrees C. Cytotoxicity tests with Calu-3 cells showed no toxic effects of the nanoparticles, whereas a partially reversible cilio-inhibiting effect on the ciliary beat frequency of chicken trachea was observed. In vivo uptake studies indicated the transport of FITC-albumin-associated TMC nanoparticles across the nasal mucosa. In conclusion, TMC nanoparticles are a potential new delivery system for transport of proteins through the nasal mucosa.

Uptake of fluorescein isothiocyanate-labelled dextran into the CSF after intranasal and intravenous administration to rats

With the growing number of patients suffering from central nervous system (CNS) diseases a suitable approach for drug targeting to the brain becomes more and more important. In the present study, the contribution of the nose-CSF pathway to the uptake of the model drug fluorescein isothiocyanate-labelled dextran with a molecular weight of 3.0 kDa (FD3) into the CSF was determined in rats. FD3 was administered intranasally (489 microg/rat) and by intravenous infusion (24.4 microg/ml; 119 microg/rat) in the same set of animals (n=6). Blood samples were taken from the tail vein and CSF was sampled by cisternal puncture using a stereotaxic frame. The contribution of the olfactory pathway to the uptake of FD3 into the CSF was determined by comparing the AUCCSF/AUCplasma ratios after intranasal and after intravenous application of FD3 mimicking the blood levels after intranasal delivery. No significant difference was observed between the AUCCSF/AUCplasma ratios of FD3 after intranasal administration (1.33+/-0.40%) and intravenous infusion (1.03+/-0.56%). This indicates that in rats about 1% of the amount of FD3 in plasma reaches the CSF both after nasal and intravenous administration and that no direct transport of FD3 from the nose-CSF could be found.

Uptake of melatonin into the cerebrospinal fluid after nasal and intravenous delivery: studies in rats and comparison with a human study

PURPOSE

To investigate the possibility of direct transport of melatonin from the nasal cavity into the cerebrospinal fluid (CSF) after nasal administration in rats and to compare the animal results with a human study.

METHODS

Rats (n = 8) were given melatonin both intranasally in one nostril (40 microg/rat) and intravenously by bolus injection (40 microg/rat) into the jugular vein using a Vascular Access Port. Just before and after drug administration, blood and CSF samples were taken and analyzed by HPLC.

RESULTS

Melatonin is quickly absorbed in plasma (T(max) = 2.5 min) and shows a delayed uptake into CSF (T(max) = 15 min) after nasal administration. The melatonin concentration-time profiles in plasma and CSF are comparable to those after intravenous delivery. The AUC(CSF)/AUC(plasma) ratio after nasal delivery (32.7 +/- 6.3%) does not differ from the one after intravenous injection (46.0 +/- 10.4%), which indicates that melatonin enters the CSF via the blood circulation across the blood-brain barrier. This demonstrates that there is no additional transport via the nose-CSF pathway. These results resemble the outcome of a human study.

CONCLUSIONS

The current results in rats show that there is no additional uptake of melatonin in the CSF after nasal delivery compared to intravenous administration. This is in accordance with the results found in humans, indicating that animal experiments could be predictive for the human situation when studying nose-CSF transport.

Uptake of estradiol or progesterone into the CSF following intranasal and intravenous delivery in rats

The uptake of estradiol and progesterone into the cerebrospinal fluid (CSF) after intranasal and intravenous administration in rats was investigated. Each animal received estradiol intranasally (40 microg/rat) and by intravenous infusion (10 microg/rat) into the jugular vein using a vascular access port. Hereafter, the same set of rats was treated with progesterone intranasally (200 microg/rat) and by intravenous infusion (104 microg/rat). Following nasal delivery, both steroid hormones reach Cmax values in plasma and CSF at 15 min after administration. Intravenous infusion of estradiol and progesterone shows comparable plasma and CSF concentration-time profiles compared to the nasal route. For both hormones the AUCCSF/AUCplasma ratios (mean +/- SD) after intranasal delivery (estradiol 2.3 +/- 1.1%; progesterone 1.9 +/- 0.7%) do not differ significantly from the ratios shown after intravenous infusion (estradiol 2.0 +/- 0.6%; progesterone 2.2 +/- 0.8%). These results indicate that after nasal delivery estradiol and progesterone are rapidly absorbed into the systemic circulation, from where the non-protein bound hormones probably enter the CSF by crossing the blood-brain barrier. No extra direct nose-CSF transport could be demonstrated.

Serial cerebrospinal fluid sampling in a rat model to study drug uptake from the nasal cavity

Drug transport from the nasal cavity to the brain has gained much interest in the last decade. In the present study, a model was developed to determine the uptake of drugs into the cerebrospinal fluid (CSF) after nasal delivery in rats. CSF samples were taken using a cisternal puncture method. In this method, a needle is advanced through the skin and muscles overlying the atlanto-occipital membrane into the cisterna magna, while the rat is fixed in a stereotaxic frame. This method appears to be superior over cannulation of the atlanto-occipital membrane for CSF sampling. The major advantages of the puncture method is the ability of serial and simultaneous CSF and blood sampling for over 2 h in the same rat. To obtain maximal drug absorption from the nasal cavity and uptake into CSF, different positions of the rat's head (upright-90 degrees, supine-90 degrees, supine-45 degrees and supine-70 degrees angles) were tested in nasal delivery studies using hydrocortisone (HC) as a model drug. Putting the rat in the supine-90 degrees angle position increased the absorption of HC into plasma and CSF 2-fold compared to the upright-90 degrees angle position. The supine-70 degrees angle position did not change the HC plasma and CSF levels compared to the supine-90 degrees angle position. However, the supine-70 degrees angle position showed the fastest CSF sampling rate, enabling more accurate CSF sampling and therefore preferred for further studies. In conclusion, the cisternal puncture method using the supine-70 degrees and 90 degrees angle position is a suitable method to study drug transport from the nasal cavity into the CSF, with the ability of multiple CSF sampling.

Classification of cilio-inhibiting effects of nasal drugs

OBJECTIVE/HYPOTHESIS

Nasal drug formulations are widely used for a local therapeutic effect, but are also used for systemic drug delivery. In the development of new nasal drugs, the toxic effects on the mucociliary clearance and therefore on the ciliated tissue is of importance. In this study, the effect of nasal drugs and their excipients on the ciliary beat frequency (CBF) is investigated.

STUDY DESIGN

Experimental, in vitro.

METHODS

CBF is measured by a photograph-electric registration method. Excised ciliated chicken trachea tissue is incubated for 15 minutes in the formulation, followed by a reversibility test. To estimate the ciliostatic potential, a classification is given of all tested formulations. According to the CBF, after 60 minutes every drug or excipient could be classified as follows: cilio-friendly: after 60 minutes the CBF has regained 75% or more of its initial frequency; cilio-inhibiting: after 60 minutes the CBF has regained between 25% and 75% of its initial frequency; or ciliostatic: after 60 minutes the CBF has regained 25% or less of its initial frequency.

RESULTS

Most formulations used are cilio-friendly or cilio-inhibiting. Only some are ciliostatic. Preservatives have a major role in the cilio-inhibiting effect of the drug. Also, other additives can contribute to the toxicity profile of nasal drug formulations.

CONCLUSION

This classification of the cilio-inhibiting potential of nasal drug formulations is a valuable tool in the design of safe nasal drugs. The number of animal studies in vivo can be reduced substantially by using this in vitro screening technique. This study demonstrates that the effect on ciliary movement of most drug formulations is due to the preservatives and/or additives and mostly not to the drug itself.

Effects of N-trimethyl chitosan chloride, a novel absorption enhancer, on caco-2 intestinal epithelia and the ciliary beat frequency of chicken embryo trachea

N-trimethyl chitosan (TMC) polymers are quaternized chitosans in different degrees of trimethylation. These polymers enhance the absorption of macromolecules through mucosal epithelia by triggering the reversible opening of tight junctions and only allow for paracellular transport. To investigate the safety of these novel absorption enhancers cytotoxicity and ciliotoxicity studies have been performed. Intestinal Caco-2 cell monolayers were chosen to study possible membrane damaging effects of these polymers, using confocal laser scanning microscopy visualization of nuclear staining by a membrane impermeable fluorescent probe during transport of the paracellular marker Texas red dextran (MW 10 000). Ciliated chicken embryo trachea tissue was used to study the effect of the polymers on the ciliary beat frequency (CBF) in vitro. In both studies the TMC polymers of different degrees of substitution (20, 40 and 60%) were tested at a concentration of 1.0% (w/v). No substantial cell membrane damage could be detected on the Caco-2 cells treated with TMCs, while the effect on the CBF in vitro was found to be marginal. TMC60 and TMC40 enhance paracellular transport of Texas red dextran in Caco-2 cell monolayers, whereas TMC20 is ineffective. In conclusion, TMCs of high degrees of substitution may be effective and safe absorption enhancers for peptide and protein drug delivery.

Validation of animal experiments on ciliary function in vitro. I. The influence of substances used clinically

In vitro studies of ciliary activity require specimens of healthy epithelium in relatively large quantities. Since human material is difficult to obtain, fresh chicken trachea samples have frequently been used in function experiments. The aim of the present study was to investigate whether several substances had comparable effects on the ciliary beat frequency (CBF) of chicken trachea and cryopreserved human respiratory epithelium obtained from the sphenoidal sinus. For this study, we used two topical anaesthetics: cocaine (3% and 7%) and lidocaine (2%). These anaesthetic substances were adjusted to pH 6 and pH 7. We also used two decongestants, namely xylometazoline 0.1% and oxymetazoline 0.1%, and the beta-blocking agent propranolol. Topical anaesthetics appeared to be more ciliostatic in solutions with pH 7 compared to pH 6. Complete ciliostatic effects were reversible, with the exception of the ciliostasis induced by propranolol. The effects of these substances on the CBF of fresh chicken trachea and cryopreserved human tissue did not differ significantly. These experiments show that chicken trachea constitutes a valid substitute for human material in studying ciliary activity in vitro. Moreover, the experiments provide evidence in support of the assumption that cryopreservation has no effect on ciliary reactivity as expressed by the CBF.

Validation of animal experiments on ciliary function in vitro. II. The influence of absorption enhancers, preservatives and physiologic saline

Ciliary beat frequency (CBF) is one of the most important parameters of mucociliary clearance. Previously, we demonstrated that mucosa from chicken embryo trachea is a good substitute for human ciliated epithelium to study the effects on CBF of substances that are used clinically. In this study, we examined the effect on CBF of four excipients for nasal drug formulations: the absorption enhancers methylated beta-cyclodextrin 2% and sodium taurodihydrofusidate 1%, the preservative benzalkonium chloride 0.01%, and physiologic saline. We also examined the effect on CBF of the cryopreservative dimethyl sulfoxide, which is used to protect ciliated epithelium prior to storage in liquid nitrogen. Results obtained with chicken embryo trachea were compared with those of cryopreserved human mucosa taken from the sphenoidal sinus. For all of the substances tested, the effects on CBF of chicken material were comparable to those measured on human material. Benzalkonium chloride had a stronger ciliostatic effect on human tissue. After 60 min, however, the effect of that substance on CBF was similar in both tissues. We conclude that chicken embryo trachea can be used as a substitute for human ciliated mucosa when studying ciliary activity in vitro.

Nasal absorption of dihydroergotamine from liquid and powder formulations in rabbits

Nasal drug delivery is an interesting route of administration for dihydroergotamine in migraine therapy. The currently available formulation contains dihydroergotamine at 4 mg/mL. For a nasal dose of 2 mg, a volume of 0.5 mL has to be administered, which sometimes leads to spillage of the formulation. The aim of the present study was to develop a nasal spray with a dihydroergotamine concentration of 10 mg/mL. To increase the solubility and stability of dihydroergotamine, randomly methylated beta-cyclodextrin was used. Liquid formulations and lyophilized powders of dihydroergotamine and randomly methylated beta-cyclodextrin were prepared. The liquid and powder formulations were compared by determining their pharmacokinetics and absolute bioavailability after nasal administration in rabbits. Nasal sprays were significantly more effective than drops in increasing the nasal bioavailability of dihydroergotamine, but the amount of randomly methylated beta-cyclodextrin in liquid sprays did not significantly alter the nasal absorption. For powder formulations, the dihydroergotamine absorption was dependent on the amount of methylated beta-cyclodextrin and powder volume, and the nasal bioavailability from the optimal powder was slightly, but not significantly, higher than that for liquids. In conclusion, the formulations investigated are a substantial improvement of the current commercial formulation, not only because the spray volume of the liquid spray can be reduced 2.5 times, but also because of the increased stability of liquid and powder sprays with randomly methylated-beta-cyclodextrin.

Confocal laser scanning microscopic visualization of the transport of dextrans after nasal administration to rats: effects of absorption enhancers

PURPOSE

To visualize the transport pathway(s) of high molecular weight model compounds across rat nasal epithelium in vivo using confocal laser scanning microscopy. Furthermore, the influence of nasal absorption enhancers (randomly methylated beta-cyclodextrin and sodium taurodihydrofusidate) on this transport was studied.

METHODS

Fluorescein isothiocyanate (FITC)-labelled dextrans with a molecular weight of 3,000 or 10,000 Da were administered intranasally to rats. Fifteen minutes after administration the tissue was fixed with Bouin. The nasal septum was surgically removed and stained with Evans Blue protein stain or DiIC18(5) lipid stain prior to visualization with the confocal laser scanning microscope.

RESULTS

Transport of FITC-dextran 3,000 across nasal epithelium occurred via the paracellular pathway. Endocytosis of FITC-dextran 3,000 was also shown. In the presence of randomly methylated beta-cyclodextrin 2% (w/v) similar transport pathways for FITC-dextran 3,000 were observed. With sodium taurodihydrofusidate 1% (w/v) the transport route was also paracellular with endocytosis, but cells were swollen and mucus was extruded into the nasal cavity. For FITC-dextran 10,000 hardly any transport was observed without enhancer, or after co-administration with randomly methylated beta-cyclodextrin 2% (w/v). Co-administration with sodium taurodihydrofusidate 1% (w/v) resulted in paracellular transport of FITC-dextran 10,000, but morphological changes, i.e. swelling of cells and mucus extrusion, were observed.

CONCLUSIONS

Confocal laser scanning microscopy is a suitable approach to visualize the transport pathways of high molecular weight hydrophilic compounds across nasal epithelium, and to study the effects of absorption enhancers on drug transport and cell morphology.

Simplified solid-phase extraction method for determination of dihydroergotamine in rabbit and human serum using high-performance liquid chromatography with fluorescence detection

A rapid, selective and sensitive method for the determination of dihydroergotamine (DHE) in serum was developed. Dihydroergocristine (DHEC) was used as an internal standard. Human and rabbit serum samples were extracted using commercial solid-phase cyano (CN) columns. Proteins were washed from these columns with pure acetonitrile, resulting in clean extracts. Extracts were subsequently separated by HPLC in an isocratic way, using a reversed-phase C18 analytical column. Fluorometric detection was performed at excitation and emission wavelengths of 277 and 348 nm, respectively. Calibration curves with amounts of DHE ranging from 2 to 32 ng, were linear. The limit of detection found for DHE was 0.2 ng, extracted from 0.5 ml rabbit or from 2.5 ml human serum. The limit of quantification in serum of both species was 0.7 ng. The method has been shown to be suitable for monitoring DHE in serum during pharmacokinetic studies in rabbits.

Effects of absorption enhancers on rat nasal epithelium in vivo: release of marker compounds in the nasal cavity

PURPOSE

The assessment of the effects of nasal absorption enhancers on the rat nasal epithelium and membrane permeability in vivo after a single nasal dose of the enhancers.

METHODS

The release of marker compounds (protein, cholesterol and acid phosphatase) from the nasal epithelium was measured using a lavage technique. The nasal membrane permeability was determined after intravenous administration of a systemic tracer (FITC-albumin).

RESULTS

The effects of the absorption enhancers could be classified into four categories. The first consisted of HP beta CD (5%), DM beta CD (2%) and RAMEB (2%) and was not different from the control (physiological saline). For the second category, DM beta CD (5%), effects were significantly higher than for the control. The third category, SGC (1%), was more active than DM beta CD (5%) but less active than the last group. The fourth, most membrane damaging, category consisted of STDHF (1%), laureth-9 (1%) and LPC (1%). Administration of these three enhancers also resulted in release of acid phosphatase, indicating that severe membrane damage occurred. The release of cholesterol from nasal epithelium was largely dependent on the cholesterol solubilisation of the absorption enhancers. The amount of cholesterol released by laureth-9 and LPC was the largest.

CONCLUSIONS

The results of this in vivo study are in agreement (i.e. similarity in rank order) with morphological and ciliotoxicity studies of nasal absorption enhancers, demonstrating that this in vivo model is a valuable tool to classify nasal absorption enhancers according to their effects on the rat nasal epithelium.

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.

Hypocalcemic effect of salmon calcitonin following single and repeated nasal and intravenous administration in young rabbits

The effect of the polypeptide salmon calcitonin (sCT) on serum calcium concentrations following intranasal and intravenous administration was studied in young rabbits. A small, hypocalcemic effect was observed after nasal administration of sCT without additives, indicating that the nasal sCT absorption was low. The absorption could be improved by addition of an absorption-enhancing adjuvant to the nasal preparation. The absorption, however, was still far from complete as was apparent from the much stronger effect of intravenously injected sCT. When a number of sCT doses were given during a 10-week period, the hypocalcemic effect per sCT dose in the young rabbits decreased after intravenous and, although less pronounced, after nasal administration. The decreased response to sCT is probably not related to the induction of neutralizing antibodies or desensitization of sCT receptors, but is more likely associated with the age-dependent level of bone activity.

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

1. The systemic absorption and the neurotrophic effect of the metabolically stabilized ACTH (4-9) analogue, Org2766, were investigated following intranasal (i.n.) administration. 2. Without additives the nasal bioavailability of the peptide was in the order of 15 and 10% in rats and rabbits, respectively. The absorption could be improved by addition of a variety of absorption enhancers to the nasal preparation. The beta-cyclodextrin derivative, dimethyl-beta-cyclodextrin (DM beta CD) at a concentration of 5% (w/v) improved the absorption in rats about 5 fold from 13 +/- 4% (mean +/- s.d.) for administration of the peptide alone to 65 +/- 21%, and in rabbits 1 to 2 fold, from 10 +/- 6% to 17 +/- 8%. 3. The increased permeability of the rat nasal mucosa for Org2766 caused by DM beta CD in rats reversed substantially within 1 h. However, the nasal absorption had not yet completely returned to the level without enhancer. 4. S.c. administered Org2766 accelerated the functional recovery from peripheral nerve damage in rats. However, the peptide did not facilitate nerve repair following i.n. administration with DM beta CD, in spite of the fact that Org2766 was well absorbed. I.v. injection of Org2766 was also ineffective.

Nasal insulin delivery with dimethyl-beta-cyclodextrin as an absorption enhancer in rabbits: powder more effective than liquid formulations

The nasal absorption of insulin using dimethyl-beta-cyclodextrin (DM beta CD) as an absorption enhancer in rabbits was studied. The nasal administration of insulin/DM beta CD liquid formulations did not result in significant changes in serum insulin and blood glucose concentrations. In contrast, previous experiments in rats showed that the addition of DM beta CD to the liquid nasal formulation resulted in an almost-complete insulin absorption, with a concomitant strong hypoglycaemic response. Apparently, the effect of the cyclodextrin derivative on insulin absorption differs between animal species following nasal delivery of insulin/DM beta CD solutions. On the other hand, nasal administration of the lyophilized insulin/DM beta CD powder dosage form in rabbits resulted in increased serum insulin concentrations, and a maximum decrease in blood glucose of about 50%. The absolute bioavailability of the nasally administered insulin/DM beta CD powder was 13 +/- 4%, compared to 1 +/- 1% for both an insulin/DM beta CD liquid and an insulin/lactose powder formulation. It is concluded that insulin powder formulations with DM beta CD as an absorption enhancer are much more effective than liquid formulations.

Absorption enhancing effect of cyclodextrins on intranasally administered insulin in rats

The absorption enhancing effect of alpha-, beta-, and gamma-cyclodextrin (CD), dimethyl-beta-cyclodextrin (DM beta CD), and hydroxypropyl-beta-cyclodextrin (HP beta CD) on intranasally administered insulin was investigated in rats. Coadministration of 5% (w/v) DM beta CD to the insulin solution resulted in a high bioavailability, 108.9 +/- 36.4% (mean +/- SD, n = 6), compared to i.v. administration, and a strong decrease in blood glucose levels, to 25% of their initial values. Coadministration of 5% alpha-CD gave rise to an insulin bioavailability of 27.7 +/- 11.5% (mean +/- SD, n = 6) and a decrease in blood glucose to 50% of its initial value. The rate of insulin absorption and the concomitant hypoglycemic response were delayed for the alpha-CD-containing solution as compared to the DM beta CD preparation. The other CDs, HP beta CD (5%), beta-CD (1.8%), and gamma-CD (5%), did not have significant effects on nasal insulin absorption. DM beta CD at a concentration of 5% (w/v) induces ciliostasis as measured on chicken embryo tracheal tissue in vitro, but this effect is reversible. In conclusion, DM beta CD is a potent enhancer of nasal insulin absorption in rats.