Electroencephalographic effects and serum concentrations after intranasal and intravenous administration of diazepam to healthy volunteers.

AIMS: To evaluate the electroencephalographic (EEG) effects, blood concentrations, vehicle irritation and dose-effect relationships for diazepam administered nasally. METHODS: The study had a cross-over design with eight healthy volunteers (one drop out). It consisted of four legs with four different administrations: intranasal (i.n.) placebo, 4 mg diazepam i.n., 7 mg diazepam i.n. and 5 mg intravenous (i.v.) diazepam. Polyethylene glycol 300 (PEG300) was used as a vehicle in the nasal formulations to solubilize a clinically relevant dose of diazepam. Changes in N100, P200 and P300 brain event-related potentials (ERP) elicited by auditory stimulation and electroencephalographic beta-activity were used to assess effects on neurological activity. RESULTS: The mean [95% confidence intervals] differences between before and after drug administration values of P300-N100 amplitude differences were -0.9 [-6.5, 4.7], -6.4 [-10.1, -2,7], -8.6 [-11.4, -5.8] and -9.6 [-12.1, -7.1] for placebo, 4 mg i.n., 7 mg i.n. and 5 mg i.v. diazepam, respectively, indicating statistically significant drug induced effects. The bioavailabilities of 4 and 7 mg i.n. formulations, were found to be similar, 45% [32, 58] and 42% [22, 62], respectively. CONCLUSION: The present study indicates that it is possible to deliver a clinically effective nasal dose of diazepam for the acute treatment of epilepsy, using PEG300 as a solubilizer.

Nasal bioavailability of peptide T in rabbits: absorption enhancement by sodium glycocholate and glycofurol.

The aim of the present study was to investigate the absolute nasal bioavailability of Peptide T from aqueous formulations containing sodium glycocholate, an absorption enhancer with known effect on epithelial tight junctions, and/or glycofurol in a crossover study in rabbits. Additionally, the reversibility of the absorption enhancing effect of sodium glycocholate was studied by applying enhancer and peptide T with different time intervals and calculating Area Under the Curve of the peptide in plasma. It was shown that the bioavailability of Peptide T was significantly enhanced when glycofurol or sodium glycocholate was added to a nasal formulation. The nasal bioavailability of Peptide T in water (control formulation), 5% glycofurol, 5% glycofurol+1% sodium glycocholate and 1% sodium glycocholate was 5.9, 22, 29 and 59%, respectively. As indicated by the differences in t(max), C(max) and time-concentration profiles different patterns of Peptide T absorption were seen from the vehicles containing glycofurol and sodium glycocholate. In the reversibility study, the enhancing effect of sodium glycocholate on nasal absorption of Peptide T was found to be reversible within 4 h. It was concluded, that nasal absorption of Peptide T in rabbits was effectively enhanced by co-administration of sodium glycocholate, which also provided very fast absorption rates as well as a relatively short lasting effect of the absorption enhancing effect. Co-administration of glycofurol leads to enhanced and prolonged absorption of the peptide. Combining the two enhancers did not lead to increased peptide T absorption compared to 5% glycofurol alone.

Solubilization and stability of bumetanide in vehicles for intranasal administration, a pilot study.

The solubility of bumetanide in vehicles of various polarities, suitable for intranasal administration in acute situations, has been investigated. The solubility at 4 degrees C in glycofurol and polyethylene glycol 200 was high (167 and 143 mg/mL, respectively), decreasing exponentially with addition of phosphate buffer or coconut oil. Vehicles containing coconut oil and glycofurol did not seem to improve the solubility relative to mixtures between glycofurol and buffer. Adequate solubility (approximately 50 mg/mL) was achieved in vehicles containing about 80% cosolvent. The stability of bumetanide was studied at 5 degrees C and 57 degrees C. No degradation was observed at low temperature. At high temperature, bumetanide decomposes in nonaqueous vehicles with half-lifes ranging from 69 to 400 days, but sufficient stability may be obtained by adjustment of pH to 7.4. It may be concluded that it is possible to prepare a clinically relevant formulation for intranasal delivery of bumetanide.

Intranasal bioavailability of buprenorphine in rabbit correlated to sheep and man.

The purpose of the present study of buprenorphine is to add information about the correlation between various animal models and nasal bioavailabilities in man. PEG 300 was added to one formulation to study whether the addition of the co-solvent results in the same absorption pattern as seen for sheep. The bioavailability of intranasal buprenorphine 0.6 mg in PEG 300 and 5% dextrose was assessed in a cross-over study in six rabbits. The mean bioavailabilities, Tmax and Cmax were 46% (S.D. +/-13) and 53% (S.D. +/-17), 8 and 12 min, 28 and 27 ng/ml for 30% PEG 300 and 5% dextrose, respectively. No significant differences were found between the nasal buprenorphine formulations. The bioavailabilities in rabbit and sheep, respectively, were approximately 2.5 and four times higher than for man. The absorption rate was faster for rabbit and sheep than for man. It appears that rabbit and sheep bioavailability differ from humans, especially with respect to rate. PEG 300 do not increase the bioavailability of buprenorphine.

Intranasal absorption of buprenorphine--in vivo bioavailability study in sheep.

The bioavailability of buprenorphine, HCl (BPP) in sheep after nasal administration of two formulations has been studied. 0.9 mg BPP in 150 microl was administered nasally and compared to 0.6 mg i.v. The test solutions were formulated with 30% polyethylene glycol 300 (PEG 300) and 5% dextrose, respectively. The bioavailability for PEG 300 was 70% (S.D.+/-27%, n=6), whereas the bioavailability for 5% dextrose was 89% (S.D.+/-23%, n=6). A two-compartment model with initial and terminal serum half-lives of 10 and 23 min, respectively, may describe the pharmacokinetics. The rate of absorption for both nasal formulations was very fast (t(max)=10 min). The C(max) was 37 ng/ml (S.D.+/-17) and 48 (S.D.+/-10) for PEG 300 and dextrose, respectively. No significant difference was found between the two formulations, but PEG 300 has advantages in relation to freezing point depression and solubility, which may be considered if further studies are going to be initiated. The high nasal bioavailability and short time to maximal plasma concentration suggests that it is possible to make a clinically relevant nasal formulation of BPP for the treatment of pain.

Intranasal administration of different liquid formulations of bumetanide to rabbits.

The bioavailability of bumetanide in rabbits after intranasal administration of eight formulations intended for use in acute situations has been studied. The vehicles tested were combinations of phosphate buffer, pH 7.4, glycofurol 75. polyethylene glycol 200 and coconut oil. A mixture of 51% glycofurol in polyethylene glycol 200 was administered containing doses of 1 and 8 mg bumetanide respectively. For all other formulations the lower dose level only was studied. The tmax obtained ranged from 3 to 10 min. The vehicles resulting in the highest rate of absorption were 60% glycofurol in coconut oil and pure glycofurol. The observed bioavailability for the different formulations ranged from 16 to 37% for the time period 0-120 min. The bioavailability was also calculated omitting the initial peak seen after i.v. injection, which may be undesirable. Using this method bioavailabilities of 33-82, for the time interval 5-120 min was found. The study also demonstrated that the total amount of bumetanide absorbed increased proportionally to the dose administered. The rate of absorption of bumetanide from all formulations tested may be relevant for the treatment of acute oedematous states. The tmax obtained after intranasal administration was shorter than reported for other non-parenteral routes of administration.

Single- and repeated-dose local toxicity in the nasal cavity of rabbits after intranasal administration of different glycols for formulations containing benzodiazepines.

To furnish a systemic effect after intranasal administration, a formulation must contain the therapeutic dose in no more than 150 L, the maximum volume that can be applied as a single administration in one nostril in man. The objectives of these studies were to examine the local toxicity of formulations containing benzodiazepines and to document the effects to support clinical trials in man. After stability, pharmacological and pharmacokinetic studies of several benzodiazepine formulations, we studied nasal toxicity after single and repeated administration to rabbits of poly(ethylene glycol) 200, tetra(ethylene glycol), glycofurolum and mixtures of these vehicles both with and without benzodiazepines. Single-dose studies with examinations 5 or 10min after application were undertaken with poly(ethylene glycol), tetra(ethylene glycol), glycofurolum and tetra(ethylene glycol)-glycofurolum in the ratio 95:5; the reactions were similar to that after physiological saline. A 14-day repeated-dose study was conducted with diazepam, lorazepam and flunitrazepam formulations in poly(ethylene glycol), and flunitrazepam in poly(ethylene glycol)-glycofurolum in the ratio 70:30; the two vehicles without any benzodiazepine were also examined. Microscopic study revealed mild changes only in the treated groups. A final four-week study was conducted with repeated administration of clonazepam formulated in tetra(ethylene glycol)-glycofurolum in the ratio 95:5; microscopy revealed mild changes after three 150-microL doses daily, but no abnormalities after one or three 100-microL doses daily. It was concluded that these three solvents individually or as mixtures resulted in only mild local toxicity and might be acceptable as vehicles in nasal preparations of benzodiazepines and other non-irritating drugs for short-term use in man.

Intranasal absorption of melatonin in vivo bioavailability study.

The bioavailability of melatonin in rabbits after nasal administration of two formulations has been studied. In each case, a total amount of 1.5 mg melatonin in 50 microl was administered and compared with 1.5 mg i.v. The test solutions were formulated with 40% polyethylene glycol 300 (PEG 300), one with 1% sodium glycocholate (+GC) and one without (-GC). The bioavailability for +GC was 94% (S.D.+/-29%, n=4), whereas the bioavailability for -GC was 55% (S.D.+/-17%, n=6). These results indicate that GC has an enhancer effect (P<0.05). However, the relatively high bioavailability without GC shows that it might not be necessary to use an enhancer for a clinical relevant formulation. The pharmacokinetics of melatonin could be described by a one-compartment model, and the serum half-life was about 13 min. The absorption rate for both formulations was very fast (tmax=5 min) and Cmax mean was 493+/-290 ng/ml (n=4) and 249+/-125 ng/ml (n=6) for +GC and -GC, respectively.

Intranasal administration of diazepam aiming at the treatment of acute seizures: clinical trials in healthy volunteers.

Intranasal administration of diazepam may be a practical alternative to the conventional acute medication of seizures, such as status epilepticus. Nine healthy students participated in an open crossover study on intranasal versus intravenous administration of diazepam (2 mg). Blood samples were collected, pharmacodynamic tests were performed, and the volunteers filled out questionnaire. Peak concentration was achieved after 18+/-11 min and the bioavailability was 50.4+/-23.3%. A pharmacodynamic effect was observed after about 5 min, but the dose, even for i.v. administration, was too low to generate a strong measurable effect. The results indicate that intranasally administered diazepam may be an effective alternative to i.v. administration in relief of seizures, e.g. in an acute situation when a physician or nurse is not available on location.

High-performance liquid chromatographic analysis of melatonin in human plasma and rabbit serum with on-line column enrichment.

This paper describes the development of a simple and sensitive analytical method for the quantification of melatonin in human plasma and rabbit serum, using standard analytical equipment and on-line column enrichment without prior extraction, clean-up or derivatization. The analytical procedure was found to be accurate, precise and linear. For human plasma, the accuracy was 101% (range 89-106%), and the mean precision was 5% (range 2-9%) for all concentrations (0, 2, 10, 50 and 200 ng/ml) tested (n=6). The accuracy in rabbit serum was 101% (range 90-112%), and the mean precision was 13% (range 8-19%) for all concentrations (0, 2, 10, 50, 200 and 500 ng/ml) tested (n=6). The retention time of melatonin was about 8 min and the total recoveries were found to be approximately 65 and 85%, respectively, for human plasma and rabbit serum. The limit of detection was found to be lower than 1 ng/ml for human plasma and around 2 ng/ml for rabbit serum. The method is, therefore, found to be suitable for melatonin bioavailability studies in rabbits and presumably also in humans.

Pharmacokinetic and pharmacodynamic response after intranasal administration of diazepam to rabbits.

Nasal application of drugs might be an alternative to intravenous administration in acute situations such as epileptic or fever seizures. In the search for a nasal formulation leading to a peak plasma concentration of diazepam at a tmax < or = 5 min bioavailability in rabbits has been studied after intranasal administration of the drug in ten vehicles of different polarity. The animals were dosed with 3 mg diazepam, dissolved in 100 microL vehicle, the solution being administered into both nostrils. The bioavailability, measured during the first 30 min, because periods after this are not relevant for acute treatment, was found to be between 49 and 62% for the four most promising vehicles, pure glycofurol 75, tetraethyleneglycol, poly(ethylene glycol) 200 and 30% glycofurol in tetraethyleneglycol. The tmax for these vehicles was achieved after 5 min, and they induced a very rapid pharmacodynamic response after 1.5 to 3.5 min. The bioavailability was reduced when more polar liquids such as ethanol and tween 20, or lipid oils, e.g. vegetable oil and miglyol 840 were added to the glycofurol. There was a good correlation between tmax and the induction of pharmacodynamic response. These results suggest that nasal application of diazepam in a water-free low-molecular-weight glycol might be of clinical importance as an alternative to intravenous injection, especially in acute situations.

High-performance liquid chromatographic analysis of Peptide T in rabbit plasma with on-line column enrichment.

The present paper describes the development of a simple and sensitive analytical method for quantification of Peptide T (PT) in rabbit plasma, using standard analytical equipment and on-line column enrichment, without prior extraction, clean-up or derivatization. The analytical procedure was found to be accurate, precise and linear. The accuracy was 100% (range 97-103%) and the mean precision was 8% (range 3-14%) for all (n=6) concentrations (0, 15, 50, 100 and 200 ng/ml). The total recovery was found to be approximately 80%, and it was found to be dependent upon the injection rate onto the extraction column. The correlation between added and found concentrations was 0.9982, and the limit of detection was estimated to be around 5 ng/ml. The method is therefore found to be suitable for bioavailability studies, involving Peptide T, in rabbits.

Study of nasal enzyme activity towards insulin. In vitro.

The possibility of insulin being enzymatically degraded in contact with the nasal mucosa has been studied in vitro. The insulin concentration was followed during 3 h incubation at 37 degrees C with freshly collected human nasal wash, isolated enzymes from pig and rabbit nasal mucosal tissue, leucine aminopeptidase and microsomal aminopeptidase, respectively. The rate of degradation with human nasal wash was found to be less than or equal to 0.02 microgram/min, which indicates that less than 0.5% of an intranasally applied insulin dose may be destroyed by local enzymes during the time of absorption. The observed degradation was not found to be limiting for an intranasal application of insulin.

Insulin-carrying microspheres, in vitro studies.

Loading and release characteristics of insulin-carrying albumin and starch microspheres have been studied in vitro. The sorption characteristics of 125I-labelled insulin onto albumin microspheres were studied and were found to be completed within 5h, and the loading capacity was found to be 0.14% w/w. Insulin did not show any sorption into the matrix of the starch microspheres. The release characteristics were analyzed by high performance liquid chromatography. About 80% was released within 5-10 min from albumin microspheres and starch microspheres, respectively.

Intranasal administration of insulin to humans.

The purpose of this review is to summarize the information and experience at present available on the intranasal administration of insulin to human subjects and to describe some of the anatomical, physiological, pharmaceutical and technological factors which can affect the absorption of insulin. An overview is given of those absorption promoters which have been used in clinical insulin studies, and the possible absorption-promoting mechanisms are discussed. This review shows that the nasal route offers a promising alternative to parenteral administration. The easier administration and the acceptance by the patients is encouraging the development of new intranasal insulin preparations.

Contact sensitivity to chlorhexidine?

In a joint study, 2061 patients (1346 women and 715 men) were patch tested with chlorhexidine gluconate 1% in water, included in a standard test series. 48 patients (2.3%) showed a positive reaction. These were relatively more common in men (3.2%) than in women (1.9%). Positive reactions were most common in patients with leg eczema (6.8%) or leg ulcer (10.9%). Of the 48 patients who were patch test positive, 14 (2 with leg ulcer) were retested with chlorhexidine gluconate 0.01 and 1%. Only one with a leg ulcer was positive. These findings indicate that false positive reactions, known as "the excited skin syndrome", may arise from testing eczema patients in a standard series. The sensitizing potential of chlorhexidine may be very low, but the potential in patients with an eczema or ulcer of the leg has to be further evaluated.

Acnegenicity testing in rabbits. An objective quantification method.

An objective method for the quantification of follicular hyperkeratosis is proposed for the rabbit ear assay of acnegenicity. The area (area%) of hyperkeratinized follicles, covering a stereomicroscopic photo of the epidermis, is proposed for the quantification of the response. The uniformity of two observers' quantification was evaluated in six tested formulations. The quantification of the response in area% was found to be a suitable and objective alternative to visual scoring on a graded scale. The median relative difference between two observers' area%-quantification was found to be 26%, and there was no statistically significant difference between the two observers' quantification (p greater than 0.10). An area% of 2, 7, and 15 is preliminarily suggested to be equivalent to the lower limit for scores 1, 2 and 3 respectively.

Hepatic elimination of femoxetine in pig.

Hepatic elimination of femoxetine was studied in seven anaesthetized 40 kg pigs by means of constant rate infusions of 3-41 mg/min. (8.6-118 mumol/min.) into the portal vein. The elimination followed saturation kinetics (Michaëlis-Menten constants: Vmax 12 mg . min.-1 . kg-1 liver; Km 1.3 mg . 1-1 blood) and was characterised by high hepatic extraction, due to metabolism. The hepatic output of the active metabolite, nor-femoxetine, was very low, indicating that other metabolic pathways than demethylation were more important in the pig. The high hepatic elimination in the pig corresponds to the high first pass effect, earlier found in man, and it depends upon the infusion rate as well as the total dose.