Nasal drug delivery system of a quaternary ammonium compound: clofilium tosylate

Pharmacodynamics and potential toxicity of intranasally administered dipyrone

Dipyrone is a non-narcotic analgesic and antipyretic drug used in both pediatric and adult patients. Dipyrone solution can be used intranasally as an antipyretic agent for infants. However, dipyrone is not stable in liquid state. Therefore, a stable dipyrone formulation was developed and the antipyretic effect of the formulation was studied after intranasal administration in rabbits and rats, respectively. To guarantee dose accuracy in animal studies, effect of dose volume on the distribution of dipyrone solution in rabbit nasal cavities were studied, using gentian violet as an indicator. Animal fever model and intranasal administration methods were established. In addition, the potential toxicity of the dipyrone formulation was studied. It was shown that the nasal volume of rabbits is large enough to hold 100 microl solution. After intranasal administration, improved pharmacodynamics was obtained with the new developed dipyrone formulation compared to the normal dipyrone solution, and significantly decreased body temperature was observed 10 min after dosing. The toxicity was negligible. In conclusion, the dipyrone formulation is effective and safe for clinical medication.

Rapid-onset intranasal delivery of metoclopramide hydrochloride. Part I. Influence of formulation variables on drug absorption in anesthetized rats

Intranasal (IN) administration is a promising approach for rapid-onset delivery of medications and to circumvent their first-pass elimination when taken orally. Metoclopramide (MCP) is a potent antiemetic, effective even for preventing emesis induced by cancer chemotherapy. The feasibility of developing an efficacious intranasal formulation of metoclopramide has been undertaken in this study. The nasal absorption of MCP was studied in anesthetized rats over 60min using the in vivo in situ technique. The influence of several formulation variables, vis., pH and the addition of preservative, viscosity and absorption enhancing agents on the nasal MCP absorption was examined. The data obtained showed that MCP was well absorbed nasally where almost 90% of the drug was absorbed after 60min from the rat nasal cavity. The MCP absorption was pH-dependant such that the apparent first-order rate constant of absorption (K(app)) was almost tripled when the pH of the solution was increased from 5 to 8. However, deviation from the classical pH-partition theory was observed pointing to the role of aqueous pore pathway in MCP nasal absorption. The K(app) was significantly increased (P<0.05) by incorporation of 0.01% of the preservative benzalkonium chloride. Conversely, increasing the solution viscosity by the use of hydroxylpropyl methylcellulose adversely affected the rate of absorption. The use of enhancers namely sodium deoxycholate, sodium cholate, chitosan low and high molecular weight, protamine sulphate and poly-l-arginine resulted in significant increase in MCP absorption. The highest promoting effect was observed with the bile salt sodium deoxycholate where about 92% of the drug was absorbed in 25min from the rat nasal cavity and the K(app) showed more than two-fold increase as compared to control (from 0.0452 to 0.1017min(-1)).

Rapid-onset intranasal delivery of metoclopramide hydrochloride Part II: Safety of various absorption enhancers and pharmacokinetic evaluation

In the present study, several nasal absorption enhancers, used in metoclopramide hydrochloride (MCP HCl) nasal solutions, have been screened for their possible damaging effect in the in vitro human erythrocytes lysis experiment. Moreover, the in vivo leaching of biological markers from the rat nasal epithelium was used as a quantitative assessment for possible nasal mucosal irritation whereby the extent of release of total protein and lactate dehydrogenase (LDH) in the nasal lavage fluid was determined. Results showed that insignificant hemolysis from normal saline (P<0.05) occurred with the enhancer protamine sulphate while poly-l-arginine and sodium cholate demonstrated very low (<15%) hemolysis and caused insignificant protein and LDH release from the rat nasal mucosa. Conversely, sodium deoxycholate and chitosan polymers (either of low or high molecular weight) showed high (>60%) hemolysis in vitro and the release of the biological markers in vivo was significantly higher (P<0.05) than the control solution (no enhancer). A significant correlation (P<0.05) existed between the enhancement effect of MCP HCl nasal absorption and the amounts of protein (r=0.85) and LDH (r=0.88). Furthermore, the pharmacokinetics of MCP HCl was determined after intravenous (IV), per-oral and intranasal administration of 10mg drug dose in rabbits. The application of a nasal spray (NS) solution containing 0.5% sodium cholate resulted in a significant improvement (P<0.05) in both the rate and extent of absorption of MCP HCl where the T(max) achieved was 23.3min as compared to 50min in case of the oral solution while the area under the serum concentration-time curve (AUC(0-infinity)) were 506.1, 434.9 and 278.7microg/mlmin for IV, NS and oral solutions, respectively. These values corresponded to absolute bioavailabilities of 87.21 and 55.61% for the NS and oral solutions, respectively. It could thus be concluded that NS of MCP HCl represents a viable approach to achieving rapid and high systemic drug absorption during the emergency treatment of severe emesis.

Pharmacokinetic evaluation of ipamorelin and other peptidyl growth hormone secretagogues with emphasis on nasal absorption

1. The pharmacokinetics of three new peptidyl growth hormone secretagogues, ipamorelin (NNC 26-0161), NNC 26-0194 and NNC 26-0235, were compared with two well-known hexapeptides, GHRP-2 and GHRP-6, in the male rat following different routes of administration. 2. Following i.v. bolus injection, plasma concentrations of the peptides declined biexponentially. Ipamorelin differed markedly from the other peptides investigated, demonstrating a systemic plasma clearance 5-fold lower than that of GHRP-6. Ipamorelin was mainly excreted in the urine, whereas GHRP-6 was predominantly excreted in the bile. NNC 26-0194 and NNC 26-0235 also showed high biliary excretions. Ipamorelin and the two NNC peptides were moderately resistant towards metabolism as 60-80% of the administered dose could be recovered from bile and urine as intact peptide. 3. After intranasal application, the bioavailability of ipamorelin was estimated at approximately 20%. Higher bioavailabilities of approximately 50% were determined for NNC 26-0235, NNC 26-0194 and GHRP-2, whereas the nasal absorption of GHRP-6 was somewhat lower. Thus, the peptides could be easily transported across the nasal epithelium suggesting that the nasal route seems promising for systemic delivery of this family of peptidyl growth hormone secretagogues.

Prodrugs for nasal drug delivery

Recently, the delivery of xenobiotics via the nasal route has received increasing attention as this offers several advantages, i.e. high systemic availability, rapid onset of action. Both charged and uncharged forms of drugs can be transported across the nasal epithelium. This mucosa is rich in various metabolizing enzymes such as aldehyde dehydrogenase, glutathione transferases, epoxide hydrolases, cyt-P450-dependent monooxygenases. The presence of these enzymes may make it possible for pharmaceutical scientists to design prodrugs for better absorption and high systemic availability. Recent advances in peptide nasal delivery through prodrug modification has been thoroughly discussed in this paper. Finally, nasally delivered therapeutic agents targeted to various disease states have been examined.

Absorption, pharmacokinetics and metabolism of 14C-sumatriptan following intranasal administration to the rat

1. Studies have been carried out to investigate the absorption of sumatriptan after intranasal administration to rats. The pharmacokinetics, metabolism and excretion of 14C-sumatriptan were compared following intranasal and intravenous dosing to male and female albino rats using an aqueous buffered formulation at pH 5.5. 2. Following intravenous administration sumatriptan was eliminated from plasma with a half-life of about 1.1 h. After intranasal administration there was rapid absorption of part of the dose and two peak plasma concentrations were observed, initially at 0.5 and then at 1.5-2 h. The elimination half-life after the second peak was estimated as being about 4 h. 3. Radioactivity was largely excreted in urine (up to 89% of dose in 168 h) after both intravenous and intranasal administration, with a faster rate of excretion after intravenous dosage (73% males, 64% females within 6 h) than after intranasal dosage (37% males, 40% females within 6 h). 4. 14C-sumatriptan was the major component in urine and in extracts of faeces after both intravenous and intranasal administration. The major metabolite excreted in urine and faeces was GR49336, the indole acetic acid analogue. 5. The results of this in vivo rat study suggest that absorption of the dose via the nasal mucosa is incomplete after intranasal administration and that there is a secondary absorption phase probably reflecting oral absorption of part of the dose. The bioavailability is estimated as about 30%, for the period 0-6 h.

Systemic absorption of ocularly administered enkephalinamide and inulin in the albino rabbit: extent, pathways, and vehicle effects

The systemic absorption of ocularly applied tritiated [D-Ala2]metenkephalinamide (YAGFM) and inulin was studied in the albino rabbit with respect to rate, extent, pathways, and vehicle effects and compared with epinephrine. Peak concentration was achieved within 20 min except for inulin, for which absorption was still ongoing at 120 min. For YAGFM, the apparent absorption rate was slower than the elimination rate, thus obeying "flip-flop" pharmacokinetics. Based on the area under the plasma concentration curve from zero to 120 min, the percent of dose systemically absorbed was 36.1 +/- 4.4% for YAGFM, at least 3.3 +/- 0.2% for inulin, and 58.5 +/- 4.4% for epinephrine. This suggests that loss of drug to the systemic circulation is a more important factor in reducing the ocular absorption of YAGFM than for inulin. The conjunctival mucosa played as important a role as the nasal mucosa in the systemic absorption of YAGFM, while playing a secondary role in the case of inulin. Unlike nonpeptide drugs, the systemic absorption of ocularly administered YAGFM and inulin was not adversely affected by incorporation in 5% polyvinyl alcohol. Overall, the contact time of the instilled dose with the conjunctival and the nasal mucosae, their intrinsic permeability, and the extent of dilution of the instilled dose are key factors determining the vehicle effects on the extent of systemic absorption of ocularly applied peptides.

Transport of tyrosine and phenylalanine across the rat nasal mucosa

Transport of tyrosine (Tyr) and phenylalanine (Phe) across the rat nasal mucosa was studied using an in situ perfusion technique. It was found that both amino acids were absorbed by active, saturable transport processes. The Km and Vmax values were calculated to be 0.68 mM and 0.44 mM/hr for L-Tyr, and 0.40 mM and 0.39 mM/hr for L-Phe, respectively. The values for L-Tyr agreed well with the results previously reported. When D-Tyr and D-Phe were used as substrates, the extent of nasal absorption was significantly reduced indicating the specific affinity of the carrier for the L-amino acids. When mixtures of L-Tyr and L-Phe were used as perfusates, both amino acids were found to be concomitantly absorbed in a competitive manner. This implied that at least one common carrier system was present in the nasal mucosa. In addition the transport appears to be Na+-dependent and may require metabolic energy as a driving force as seen from the inhibition of the L-Phe uptake by ouabain and 2,4-dinitrophenol.

Effect of bile salts on nasal permeability in vitro

Nasal mucosa excised from dogs or rabbits was mounted as a flat sheet in an in vitro chamber. The permeability was assessed by measuring the unidirectional flux of the radiolabeled tracer compounds, water, sucrose, polyethylene glycol, and cholecystokinin octapeptide. The permeability coefficients calculated from the fluxes indicate that the nasal mucosa is moderately permeable to water-soluble compounds and compares with ileum or gallbladder. The addition of 0.5% sodium deoxycholate to the mucosal bathing solution caused a rapid, four- to fivefold increase in permeability to sucrose or cholecystokinin octapeptide. The increase in permeability was bidirectional, was not reversed by washing, and was accompanied by histological evidence of extensive loss of the surface epithelial layer. These results indicate that bile salts enhance nasal permeability by removing the epithelial cells, which constitute a major permeability barrier, rather than causing a chemical modification of the mucosal cells. This argues against the use of bile salts to enhance nasal drug absorption in patients.

Effect of intranasal histamine on nasal mucosal blood flow and the antidiuretic activity of desmopressin

The effects of exogenous histamine on nasal mucosal blood flow and the systemic activity of intranasally administered desmopressin, a vasopressin analogue, were studied in normal volunteers. Ten subjects received either saline or histamine (1, 20, 100, and 500 micrograms) by intranasal spray. Maximal nasal mucosal blood flow response, determined by laser doppler velocimetry, demonstrated a significant (P less than 0.05) linear relationship to histamine dose. Eight additional subjects received each of the following intranasal treatments: 20 micrograms histamine followed by 10 micrograms desmopressin; normal saline followed by 10 micrograms desmopressin; 20 micrograms histamine followed by vehicle; or normal saline and vehicle. Nasal blood flow was determined before and after each treatment. Desmopressin activity was assessed by measuring urine osmolality, flow rate, electrolyte, and creatinine concentration for 24 h after each treatment. The effect of histamine and desmopressin was greater than desmopressin alone, with respect to nasal blood flow response (103 +/- 24 vs. 4 +/- 17%, mean +/- SEM, P less than 0.02), initial urine osmolality (520 +/- 123 vs. 333 +/- 75 mosM, P less than 0.03), urine electrolyte (potassium, 45 +/- 11 vs. 28 +/- 7 meq/liter; sodium, 68 +/- 21 vs. 36 +/- 8 meq/liter, P less than 0.03) and creatinine concentrations (95 +/- 23 vs. 60 +/- 13 mg/dl, P less than 0.03), and the duration of decrease in urine flow rate compared with saline and vehicle. These results suggest that the systemic activity of intranasal desmopressin is enhanced by increasing local nasal blood flow and are consistent with increased transnasal absorption of the peptide.

Effects of dose, pH, and osmolarity on nasal absorption of secretin in rats. II: Histological aspects of the nasal mucosa in relation to the absorption variation due to the effects of pH and osmolarity

Nasal absorption of secretin in rats was enhanced in an acid solution, and the maximum absorption was observed at a sodium chloride solution molarity of 0.462. In order to examine reasons for the variation of absorbability caused by the change of pH and osmolarity in secretin preparations, both a pretreatment study, in which the nasal mucosa was treated with placebo prior to the administration of a secretin preparation, and a histological study were conducted in rats. The nasal absorption of secretin was determined by measuring the increased secretin of pancreatic juice. Similar profiles of nasal absorption, both after intranasal administration of secretin preparations and as a result of pretreatment effects, were obtained in studies of the effects of pH and osmolarity. However, in the pH-effect study, the absorption with the use of active preparations was observed to be significantly larger than that with the pretreatment effect below a pH of 4.79, and significantly smaller than that with the pretreatment effect at a pH of 7 to 8. The results of histological studies revealed structural changes of the epithelial cells of the nasal mucosa at pH 2.94, and shrinkage of epithelial cells was observed at a sodium chloride solution molarity of 0.462.

Analysis of structural requirements for the absorption of drugs and macromolecules from the nasal cavity

An octapeptide and a protein, of molecular weights 800 and 34,000, respectively, were found to have nasal bioavailabilities of 73 and 0.6%, respectively, in the rat. This data, combined with reported values for 23 other compounds, indicated good availability without adjuvants for all molecules up to 1000 molecular weight (mean 70%, SD between compounds 26%, n = 15) with a decline in availability above this value. The relationship between absorption and molecular weight was modeled assuming competition between constant clearance from the nasal cavity and molecular weight-dependent transport through the mucosa. Deviations of absorption from values predicted by this model did not correlate with factors such as charge, hydrophobicity, or susceptibility to aminopeptidases, but the relative absorption of cyclic and cross-linked peptides and proteins was significantly greater than that of linear peptides. It is argued that the most likely route for transport is through junctions between cells and that surface-active adjuvants (MW 6000) which markedly enhance insulin uptake may act by rendering hydrophobic areas of contact of the junctional proteins temporarily hydrophilic. The nasal route is suitable for efficient, rapid delivery of many molecules of molecular weight less than 1000. With the use of adjuvants, this limit can be extended to at least 6000 and possibly much higher.

Mechanism of nasal absorption of drugs I: Physicochemical parameters influencing the rate of in situ nasal absorption of drugs in rats

The effect of rate of perfusion, volume, pH of the perfusate, and partition coefficient of the drug on the rate of in situ nasal absorption in rats was examined. The studies showed that the rate constant for the nasal absorption of phenobarbital was independent of the rate of perfusion above a value of 2 mL/min. The nasal absorption of benzoic acid was found to depend on the pH of the perfusate with the benzoate anion being absorbed at a rate one-fourth of that of benzoic acid. The effect of lipid solubility on the extent of nasal absorption was studied using a series of barbiturates. The rate and extent of absorption was found to be dependent on the chloroform-water partition coefficient of the barbiturate. The effect of the volume of the perfusate on the absorption rate constant of phenobarbital, phenol red, tyrosine, and propranolol was studied. The data obtained showed that a linear relationship existed between the rate constants of absorption and the reciprocal of the volume of the perfusate. Using this in situ relationship it was possible to predict in vivo absorption rate constants for propranolol and L-tyrosine when volumes of 0.1 mL were administered. The calculated values for these compounds were found to be close to those determined in in vivo experiments. This indicates that the in situ technique can be used to predict in vivo absorption rate constants.

Nasal delivery of polypeptides I: nasal absorption of enkephalins in rats

The serum levels of two enkephalins after various routes of administration were compared in rats. The results indicated that serum levels of metkephamid after nasal administration were not significantly different than levels after intravenous injection. The oral administration of metkephamid resulted in undetectable serum levels. The effects of a promoter and variations in the peptide dose on nasal absorption were studied. Depending on the stability of the polypeptide and its susceptibility to enzymatic degradation, nasal absorption of peptides can be influenced by the presence of a promoting agent in the formulation. A linear relationship between the dose and the AUC was observed in the range of concentrations studied. The absorption mechanism appears to be passive diffusion. Microscopic examinations of nasal mucosa in rats revealed degrees of irritation which, considering the experimental exposure, were slight and probably repairable. The data indicate that enkephalins can be absorbed through the nasal mucosa into the systemic circulation, and the onset of absorption was rapid. Nasal administration may offer an attractive alternative for the delivery of proteins and/or polypeptides which are, in general, absorbed poorly when given orally.