Clinical image: Cervicofacial rotation skin flap in PLWD patients

This article outlines a surgical protocol designed for people living with dementia (PLWD). It proposes that simultaneous resection and reconstruction of skin cancer can minimizes the need for initial care. The method outlined involves primary closure via a cervicofacial rotation flap technique and the use of monofilament resorbable sutures.

Navigating the complexities and controversies of medication-related osteonecrosis of the jaw (MRONJ): a critical update and consensus statement

OBJECTIVES

To provide a critical update identifying the knowledge gaps and controversies in medication-related osteonecrosis of the jaw (MRONJ) within the Belgian healthcare context and outline opportunities for improvement and research in these areas.

METHODS

A literature review was performed to identify guidelines from international clinical societies in oncology or oral and maxillofacial surgery on diagnosing, preventing, and treating MRONJ. The recommendations were critically assessed in light of recent developments in the field and confronted with the clinical experience of experts.

RESULTS

Despite progress in the diagnostic criteria of MRONJ, the continued need for an 8-week timeout period should be reconsidered. Furthermore, 3D imaging techniques should be introduced to improve diagnosis and staging. The staging system remains ambiguous regarding Stage 0 MRONJ, and ongoing confusion exists regarding the term non-exposed MRONJ. The prevention of MRONJ should be tailored, considering the individual patient's risk of MRONJ, frailty, and life expectancy. More research seems needed into the efficacy and safety of drug holidays, considering the risks of rebound remodeling on fractures. With renewed interest in surgical and adjunct management techniques, adequately designed clinical studies are needed to help translate trial outcomes into universally applicable treatment guidelines taking into account individual patient characteristics.

CONCLUSIONS

Important knowledge gaps remain and hamper the development of clinical guidelines. Several controversies were identified where consensus is lacking, and further harmonization between stakeholders is necessary. Finally, the need for randomized controlled comparative clinical trials in MRONJ resonates harder than ever to identify the best treatment for individual patients.

Characterization of Binary Mixtures Consisting of Cross‐Linked High Amylose Starch and Hydroxypropylmethylcellulose Used in the Preparation of Controlled Release Tablets

Cross-linked amylose starch (CLA), hydroxypropylmethylcellulose (HPMC), and HPMC/CLA matrices were prepared by direct compression. HPMC was used to slow down the enzymatic degradation of CLA matrices. CLA was either granulated alone and mixed with HPMC or cogranulated with the latter. Compaction characteristics of the powder, hydration and mechanical properties of the resulting matrices, as well as the release profiles of three model drugs were investigated. The results showed that wet granulation of CLA in the presence of 10% HPMC improved significantly the flow properties of the powder without compromising its compactibility. Both CLA and HPMC deformed mainly by plastic flow (yield pressures are 75 and 124 MPa, respectively), but CLA exhibited a stronger elastic component (elastic recoveries are 18.4 and 11.5%, respectively). The values of yield pressure increased linearly with the concentration of HPMC. The addition of HPMC to CLA slightly decreased the resistance to consolidation but the crushing force of the final compacts was found to be proportional to the HPMC concentration. Mechanical studies on swollen matrices revealed that CLA formed a stronger gel than HPMC or CLA/HPMC mixture, and swelling and erosion of the tablets increased with HPMC content and incubation time. The in vitro release kinetics of three model drugs (pseudeoephedrine sulfate, sodium diclofenac, and prednisone) showed a clear effect of drug solubility and presence of alpha-amylase in the dissolution medium on the release rate. The addition of HPMC to CLA protected the tablets against alpha-amylase hydrolysis and reduced the release rate of prednisone and sodium diclofenac. The release of pseudoephedrine sulfate was fast and independent of HPMC and occurred mainly by diffusion.

Tissue reaction and biodegradation of implanted cross-linked high amylose starch in rats

The biocompatibility and degradation characteristics of cross-linked high amylose starch (Contramid were investigated in rats over 4 months. Contramid pellets (3-mm diameter and thickness) obtained by direct compression, were implanted subcutaneously and intramuscularly. On sequential time points, macroscopic observations of implantation sites were performed and tissue samples were removed, fixed, and histologically evaluated. No macroscopic inflammatory reaction was observed with Contramid.. Upon histologic examination, inflammatory reaction produced by Contramid was moderate and restricted to implantation sites. The sequence of inflammatory events with Contramid was similar regardless of implantation site. Degradation of Contramid pellets was characterized by fragmentation with formation of fibrovascular septa and phagocytosis by macrophages. Finally Contramid was mostly absorbed by the end of the 4-month period and substituted by adipocytes. It has been demonstrated that Contramid is a biocompatible and absorbable material.

Modified high amylose starch for immobilization of uricase for therapeutic application

Urate oxidase (uricase) was immobilized on carboxymethyl high amylose starch cross-linked 35 (CM-HASCL-35), on aminoethyl high amylose starch cross-linked 35, as well as on commercial supports, CNBr-activated Sepharose and diaminodipropylamine agarose. The N -ethyl-5-phenylisoxazolium-3'-sulphonate (Woodward reagent K) gave a high binding but totally inhibited the enzyme activity. Best results were obtained with CM-HASCL-35 using 1-ethyl-3-(3-dimethylaminopropyl)carbodi-imide as a coupling agent. The immobilized enzyme retained 88% of its initial limit rate [V (max)(app)=16 EU/mg for immobilized uricase versus V (max)=18 EU/mg for the free enzyme], with an apparent decrease of affinity for urate substrate [K (m)(app)=0.17 mM versus K (m)=0.03 mM for the free enzyme]. The coupling yield was 60% and the modified uricase was found more resistant to proteolysis than the free enzyme. The immobilized uricase retained 25% of its initial activity after 60 min in pancreatic proteolysis medium (pancreatin), whereas the free enzyme retained only 5% of its initial activity. The best immobilization yield was obtained with the polymeric support based on CM-HASCL-35 (53%), which gave better results than commercial supports based on agarose.

Influence of physical parameters and lubricants on the compaction properties of granulated and non-granulated cross-linked high amylose starch

Cross-linked high amylose starch (CLA) is a pharmaceutical excipient used in direct compression for the preparation of controlled release tablets and implants. In this work the compression properties of CLA in bulk and granulated forms (without binder) were evaluated for the first time. Tablets were prepared on an instrumented single punch machine. The flow properties and the compression characteristics (compressibility, densification behavior, work of compression) of the materials as well as the mechanical strength of the finished compacts (compactibility) were systematically examined. Wet granulation was found to improve the flowability and the compressibility of CLA but concomitantly reduced its compactibility. It was demonstrated that CLA was a plastically deforming material with a plasticity index and a yield pressure value comparable to those of pregelatinized starch. The compactibility of granulated CLA was independent of particle size in the range of 75 to 500 microm, but slightly decreased when the percentage of the fine particles (<75 microm) in the bulk powder was increased. Water and colloidal silicone dioxide facilitated the consolidation of CLA, while magnesium stearate had an opposite effect on the tablet crushing force.

Optimizing pH-responsive polymeric micelles for drug delivery in a cancer photodynamic therapy model

Different pH-sensitive, randomly- and terminally-alkylated N-isopropylacrylamide (NIPAM) copolymers were synthesized and used to prepare pH-responsive polymeric micelles (PM). These copolymers were modified from previously-studied copolymers by incorporating an additional hydrophilic monomer, N-vinyl-2-pyrrolidone (VP) to decrease uptake by the mononuclear phagocyte system (MPS) and improve localization in tumors. VP lowered the phase transition pH of the copolymers but did not affect the onset of micellization. The in vitro cytotoxicity of the copolymers was evaluated on EMT-6 mouse mammary tumor cells in comparison to Cremophor EL (CRM). The anticancer photosensitizer aluminum chloride phthalocyanine (AlClPc) was loaded into the PM with a standard dialysis procedure. Biodistribution and in vivo photodynamic activity were then evaluated in Balb/c mice bearing intradermal EMT-6 tumors. All NIPAM copolymers demonstrated substantially lower cell cytotoxicity than the control surfactant CRM. In vivo, similar AlClPc tumor uptake was observed for the PM and CRM formulations. However, the PM appeared to exhibit greater activity in vivo than CRM formulation at an AlClPc subtherapeutic dose. Therefore, NIPAM-based copolymers containing VP units represent promising alternatives for the formulation of poorly water-soluble phthalocyanines.

Characterization of crosslinked high amylose starch matrix implants. 2. In vivo release of ciprofloxacin

The purpose of this study was to develop a crosslinked high amylose starch (CLHAS) matrix implant as a sustained antimicrobial delivery system for local prevention and/or treatment of osteomyelitis. Implants (200 mg) of CLHAS containing 2.5% (5 mg), 7.5% (15 mg), 15.0% (30 mg) and 20.0% (40 mg) of ciprofloxacin (CFX), were prepared by direct compression of dry blends. Rabbits were administered six 2.5, two 7.5, one 15.0 or one 20.0%-CFX implants along the femur between the quadriceps and biceps femoris muscles to determine systemic (serum) versus local (muscle and bone) CFX concentrations over 1 month. Blood samples were taken throughout the study for CFX assay. Muscle and femur were collected at 3, 7, 14, 21 and 28 days after implantation for host response evaluation and CFX assay. Residual polymer was explanted to determine the remaining dose of CFX. All animals remained healthy during the study. Local tissue reaction was mild and limited to the implantation site. Serum CFX concentrations remained low regardless of implant loading. Increased drug loading resulted in a higher and longer release of CFX in muscle and in bone. Local CFX concentrations were detected largely in excess of the MIC over 28 days with 20.0%-CFX implants. More residual CFX in polymer was detected over a longer period of time at high loading. These results strongly support the development of CLHAS implants for local antibacterial therapy.

Characterization of crosslinked high amylose starch matrix implants. 1. In vitro release of ciprofloxacin

The objective of this study was to characterize in vitro the potential of crosslinked high amylose starch (CLHAS) as an implant matrix for the delivery of ciprofloxacin (CFX). Direct compression of dry blends of four different matrices: control CLHAS; CLHAS with 1% hydrogenated vegetable oil (HVO); and CLHAS with 10 or 20% hydroxypropylmethylcellulose (HPMC), each of them with three CFX loadings (2.5, 5.0 and 7.5%) was performed to prepare twelve implant formulations. All CLHAS implants were used for 24-h dissolution tests to evaluate swelling, erosion, water uptake and CFX release. Additionally, 1%-HVO- CLHAS implants were used for an extended dissolution test. The presence of HPMC in the matrix increased CFX release rate, swelling, erosion and water uptake in a concentration-dependent manner whereas HVO had no effect. With increasing drug loading, a decrease of cumulative CFX percent release was observed in both 24-h and extended dissolution tests. Of the different formulations tested, CLHAS implants with 1% HVO and 7.5% CFX provided the longest period of drug delivery without any initial burst effect.

Characterization of subcutaneous Contramid implantation: host response and delivery of a potent analog of the growth hormone-releasing factor

Cross-linked high amylose starch (Contramid) was investigated as a solid implant for evaluation of host response in mice and as a possible delivery system for a human growth hormone-releasing factor analog (Hex-hGRF) release profile in pigs. Seventy mice were administered subcutaneously one 3 mm diameter Contramid pellet and host reaction was evaluated over 6 months. Thirty pigs were divided into four groups. All animals of the three implanted groups were administered subcutaneously 15 mg Hex-hGRF, (1) one pure Hex-hGRF implant; (2) four 30/70 w/w Hex-hGRF/Contramid implants; or (3) eight 15/85 w/w Hex-hGRF/Contramid implants. The fourth group (n=6) was injected subcutaneously twice daily with 10 microg/kg of Hex-hGRF over 5 consecutive days. Serum insulin-like growth factor-I (IGF-I) was monitored over 1 month. In mice, no adverse reaction occurred after implantation. Macroscopic and microscopic inflammatory reactions were always localized. Polymorphonuclear cells (PMNs) and macrophages predominated within and around the pellets, respectively. Thin fibrovascular septas eventually subdivided Contramid pellets which were progressively phagocytosed by macrophages. In pigs, serum IGF-I concentrations were increased over a 10 day period in all implanted groups. The initial IGF-I peak observed in the daily injected group was avoided in both Contramid implant groups but not in the pure Hex-hGRF implant group. These encouraging results warrant the development of Contramid implants as a sustained delivery system for peptidic drugs.

Cross-linked high amylose starch derivatives as matrices for controlled release of high drug loadings

Selection of hydrogels as excipients in controlled drug release systems depends on the characteristics of the gel and of the drug. Three types of derivatives were synthesized from cross-linked high amylose starch (HASCL-6) by substitution of hydroxylic groups with cationic (carboxymethyl: CM), anionic (aminoethyl: AE) and acetate (Ac) groups. These new polymeric excipients are able to control the release over 20 h from monolithic tablets loaded with 20 to 60% drug. Three drugs were used as model tracer: acetaminophen (uncharged), acetylsalicylic acid (having an acidic group) and metformin (having a basic group). It was found that the release of ionic drugs from CM-HASCL-6 and AE-HASCL-6 matrices can be partially controlled by ionic interaction between pendant groups of polymer and drugs. The substitution degree of HASCL-6 derivatives can also be varied to modulate the drug's release time. These derivatives represent a novel generation of pharmaceutical excipients, recommended for high loading dosage formulations.

Enzymatic degradation of cross-linked high amylose starch tablets and its effect on in vitro release of sodium diclofenac

The influence of several physicochemical parameters on enzymatic hydrolysis and the in vitro release of sodium diclofenac (SDic) from cross-linked high amylose starch (Contramid) (CLA) tablets was evaluated. These parameters included pH, ionic strength of the medium, enzyme concentration, compression force and incorporation of gel-forming polymers such as hydroxypropyl methylcellulose (HPMC), poly(ethylene oxide) (PEO) and poly(vinyl alcohol) into the tablet. Pure CLA tablets were incubated in phosphate buffer (pH 6.8) containing alpha-amylase and the extent of enzymatic erosion was determined by gravimetry. Release of SDic from CLA tablets, in the presence of alpha-amylase, was measured using a USP type III dissolution apparatus. For low alpha-amylase concentrations (<2250 IU/l), the drug release was mainly diffusion-controlled. At higher alpha-amylase concentrations (>4500 IU/l) both diffusion and erosion contributed to the release of SDic. The hydrolysis kinetics of CLA tablets by alpha-amylase was biphasic. During the first phase (2-4 h), the hydrolysis rate was hyperbolically related to the alpha-amylase concentration but was practically alpha-amylase concentration-independent during the second phase. Enzymatic erosion and drug release kinetics appear to be relatively independent of ionic strength, pre-incubation time in simulated gastric fluid, and compression force of the tablets (6-34 kN). Incorporation of HPMC or PEO into the tablet resulted in a significant decrease of both tablet erosion and drug release rates.

In-vitro and in-vivo evaluation of pH-responsive polymeric micelles in a photodynamic cancer therapy model

pH-sensitive polymeric micelles of randomly and terminally alkylated N-isopropylacrylamide copolymers were prepared and characterized. Aluminium chloride phthalocyanine (AlClPc), a second generation sensitizer for the photodynamic therapy of cancer, was incorporated in the micelles by dialysis. Their photodynamic activities were evaluated in-vitro against EMT-6 mouse mammary tumour cells and in-vivo against EMT-6 tumours implanted intradermally on each hind thigh of Balb/c mice. pH-sensitive polymeric micelles were found to exhibit greater cytotoxicity in-vitro than control Cremophor EL formulations. In the presence of chloroquine, a weak base that raises the internal pH of acidic organelles, in-vitro experiments demonstrated the importance of endosomalllysosomal acidity for the pH-sensitive polymeric micelles to be fully effective. Biodistribution was assessed by fluorescence of tissue extracts after intravenous injection of 2 micromol kg(-1) AlClPc. The results revealed accumulation of AlClPc polymeric micelles in the liver, spleen and lungs, with a lower tumour uptake than AlClPc Cremophor EL formulations. However, polymeric micelles exhibited similar activity in-vivo to the control Cremophor EL formulations, demonstrating the higher potency of AlClPc polymeric micelles when localized in tumour tissue. It was concluded that polymeric micelles represent a good alternative to Cremophor EL preparations for the vectorization of hydrophobic drugs.

Cross-linked high amylose starch for controlled release of drugs: recent advances

Cross-linked high amylose starches have been developed as excipients for the formulation of controlled-release solid dosage forms for the oral delivery of drugs. Advantages of this new class of excipients include cost-effectiveness, readily accessible industrial manufacturing technology, high active ingredient core loading and the possibility of achieving a quasi zero-order release for most drugs. In addition to the latter, other features distinguish cross-linked high amylose starches from other excipients used to prepare hydrophilic matrices. Among these are the absence of erosion, the limited swelling and the fact that increasing cross-linking degrees results in increased water uptake rate, drug release rate and equilibrium swelling. Thus the goal of the present study was to gain some insights into the mechanism of drug release control by matrices of cross-linked high amylose starch. Water transport kinetics and dimensional changes were studied in matrices placed in water at 37 degrees C by an image analysis technique. The results show that in the first 5 min, a gel layer is formed at the surface of the tablet, after which the gel front seems to halt its progression toward the center of the tablet. Water continues to diffuse through the front and to invade the core. As a consequence, this latter swells, with a predominance for radial swelling. Equilibrium swelling is reached over 3 days, when the water concentration in the tablet becomes homogeneous and the whole tablet gelifies. Solid-state 13C-NMR were acquired on cross-linked high amylose starch powders, tablets and hydrated tablets with varying cross-linking degrees. They show a predominance of the V-type single helix arrangement of amylose in the dry state irrespective of the cross-linking degree. Upon hydration, the homologues with a low cross-linking degrees show a transition from the V to the B-type double helix arrangement. It is therefore hypothesized that the capacity of amylose to undergo the V to B transition is an important factor in controlling water transport and drug release rate. Finally applications to different drugs are reviewed briefly. They illustrate the versatility of this technology as generic versions of zero order OROS drug (Efidac) and Fickian release conventional matrices (Voltaren SR) were developed and successfully tested in pilot clinical studies to be bioequivalent to the references. These studies further showed that cross-linked high amylose starch matrices have the lowest inter-subject variability among the systems tested and show a total absence of food effect.

Image analysis studies of water transport and dimensional changes occurring in the early stages of hydration in cross-linked amylose matrices

The purpose of this work was to monitor and quantify water transport and dimensional changes occurring in the early stages of hydration in cross-linked amylose (CLA) matrices using image analysis technique. Samples were prepared by direct compression of CLA-6 powder to obtain matrices of 0.17 cm thickness and 1.295 cm in diameter. A surface gel layer was formed quasiinstantaneously. The gel expansion was then constrained and the material continuity caused the outer gel layer to be in a state of biaxial compression and the internal core in a state of biaxial tension. A diffusion front preceded the gel-glass interface even in the early stages of hydration. A delayed stress-release occurred through a radial expansion of the tablet interior. This relaxation coincided with the time at which the axial diffusion fronts met. The dimensional changes had a marked impact on the kinetics of water uptake in CLA-6 tablets in early stages of hydration.

Radioimmunoassay of meterelin and pharmacokinetics after single injection and implant administration in dogs

A sensitive and specific radioimmunoassay for a novel luteinizing-hormone-releasing-hormone (LHRH) agonist, [2-Me-D-Trp6, DesGly10]LHRH ethylamide (meterelin), was developed for documenting the pharmacokinetic parameters of this peptide following its intravenous (iv) and subcutaneous (sc) administration in dogs. The assay was also used for monitoring meterelin in plasma following its release from d,l-lactide-glycolide implants in the same species. Rabbit antisera generated against [DespyroGlu1] meterelin and conjugated to bovine serum albumin with glutaraldehyde showed high specificity, whereas crossreactivity to LHRH and its fragments and to analogs with substitutions at residues 6 and 10 was found insignificant. The assay was validated in terms of accuracy (recovery range, 94.0-105.4%), in terms of precision (intra- and interassay variations of 10.0-12.4% and 8.6-11.3%, respectively), and in terms of sensitivity (minimum detectable dose of 2.7 pg/assay). Following iv acute administration, a biexponential decline of plasma meterelin levels was observed, with distribution and elimination half-lives of 5.9 +/- 2.5 and 106 +/- 22 min, respectively. After sc acute administration, the elimination half-life was in the range of 103 to 173 min. The systemic clearance (CLT) ranged from 1.6 to 2.6 mL/min/kg, and the volume of distribution at steady state (Vdss) varied from 285 to 438 mL/kg. The elimination half-life (T1/2 beta), Vdss, and ClT were not significantly different after both routes of administration over the 1-100-microgram/kg dose range of peptide studied. Castrate levels of testosterone were attained 10 days after sc administration of the implant, lasted for up to 247 days, and were well correlated with plasma levels of meterelin.

Growth hormone release by the novel GH releasing peptide hexarelin in patients with homozygous beta-thalassemia

Patients with beta-thalassemia often present with abnormalities in growth and other endocrine functions. Growth hormone (GH) secretion is controlled via somatostatin and growth hormone releasing hormone (GHRH). Recently, Hexarelin, a new potent GH secretagogue (His-D-2-Methyl-Trp-Ala-Trp-D-Phe-Lys-NH2), was synthesized. Our study was designed to assess and compare its efficacy as a GH secretagogue to GHRH 1-29 in beta-thalassemia. Eighteen patients, regularly transfused and chelated, were studied; 11 were short statured. None had diabetes mellitus, hypothyroidism, hypopara-thyroidism or major organ failure. We measured GH at 0, 30, 60, 90, 120 min after GHRH 1-29 or Hexarelin administration. Hexarelin p.o. or i.v. evoked a brisk rise of serum GH which was significantly higher (p < 0.01) than that induced by GHRH 1-29 i.v. In conclusion, Hexarelin has greater GH releasing capacity than GHRH 1-29 at 1 microgram/kg i.v. and can thus be viewed as a potential therapeutic agent in GH deficient states.

Radioimmunoassay of Antarelix, a luteinizing hormone releasing-hormone antagonist, in plasma and its application for pharmacokinetic study in dogs

A procedure for the radioimmunoassay (RIA) of Antarelix (teverelix) in plasma has been developed for the pharmacokinetic study of this potent LHRH antagonist in dogs. Antiserum was produced by coupling the deamidated Antarelix analog to bovine serum albumin by a carbodiimide reaction and immunizing rabbits with the conjugate. The crossreactivity of the antiserum with LHRH, LHRH agonist Metereline and LHRH antagonists tested was negligible, except for Antide which displayed a crossreactivity of 33%. No crossreactivity with Antarelix metabolites could be detected. The RIA is suitable for the direct determination of Antarelix in plasma, with a minimum detectable level of 1.12 fmol/assay. The accuracy and precision of the method were assessed with plasma samples spiked with Antarelix at concentrations ranging from 0.4 to 6.4 pmol/ml. The recovery was 104.8% with intra- and interassay CV between 1 and 3.7%. Pharmacokinetic profiles of Antarelix in dogs were established following an i.v. or a s.c. dose of 10 micrograms/kg.

Radioimmunoassay for hexarelin, a peptidic growth hormone secretagogue, and its pharmacokinetic studies

A radioimmunoassay (RIA) method for hexarelin, a peptidic growth hormone secretagogue, has been developed and applied to pharmacokinetic studies in dogs following an IV dose of 1 microgram/kg, and three SC doses of 1, 10, and 100 micrograms/kg. The sensitivity of the assay was determined to be 1.34 fmol/assay. Cross-reactivity of the antiserum with nine hexarelin analogues was less than 1% upon modification of positions 3, 4, or 5 of the peptide. No apparent cross-reaction with endogenous hexarelin metabolites were observed. Intra- and interassay coefficients of variation were less than 3% and 4%, respectively. Intravenous bolus pharmacokinetics of hexarelin displayed a high terminal half-life of 120 min, a fractional plasma clearance of 4.28 ml/min/kg, and a volume of distribution at steady state of 387.7 ml/kg. Following SC administration of hexarelin, despite the increase in dose administered, both clearance (3.93-5.17 ml/min/kg) and volume of distribution (316-544 ml/kg) parameters remained constant over the dose range studied.

Modulation of growth hormone-releasing activity of hexarelin in man

Hexarelin (His-D-2-methyl-Trp-Ala-Trp-D-Phe-Lys-NH2) is a new synthetic growth hormone (GH)-releasing hexapeptide. The mechanism of action of hexarelin in man is not fully elucidated. As for other GH-releasing peptides, an action on both the pituitary gland and the hypothalamus has been hypothesized. In the present study, we evaluated the modulation of GH-releasing activity of hexarelin in man. In a first experiment conducted on 6 healthy male volunteers, we studied the interaction of the maximally effective intravenous dose of hexarelin (2 micrograms/kg i.v.) with GH-releasing hormone (GHRH, 2 micrograms/kg i.v.) and somatostatin (2 micrograms/kg/h i.v.). In a second experiment involving another 6 male subjects, we evaluated the interaction of hexarelin with neuroactive substances, such as pirenzepine (0.6 mg/kg i.v.), pyridostigmine (120 mg p.o.) and arginine (0.5 g/kg i.v.), thought to modulate endogenous somatostatin secretion. Hexarelin induced a higher increase in GH levels as compared to GHRH (integrated output calculated as area under the curve AUC0-120 4,693 +/- 691 vs. 1,494 +/- 102 micrograms.min/l, p < 0.01). Coadministration of hexarelin and GHRH produced a higher GH response than hexarelin alone (AUC0-120 7,395 +/- 450 micrograms.min/l, p < 0.05). Somatostatin abolished the GH response to GHRH (AUC0-120 363 +/- 89 micrograms.min/l, p < 0.01), while it only blunted that to hexarelin (AUC0-120 1,314 +/- 297 micrograms.min/l, p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolic modulation of the growth hormone-releasing activity of hexarelin in man

Hexarelin (His-D-2-methyl-Trp-Ala-Trp-D-Phe-Lys-NH2) is a new potent synthetic growth hormone (GH)-releasing hexapeptide. The mechanism of action of hexarelin in man has never been evaluated. Hexarelin may act directly on specific pituitary receptors and indirectly on the hypothalamus. To elucidate its mechanism of action in man, we studied the interaction of hexarelin with glucose and free fatty acids (FFA), two metabolic factors known to inhibit both basal and GH-releasing hormone (GHRH) stimulated GH secretion. Glucose is thought to inhibit GH secretion via stimulation of endogenous somatostatin release, whereas FFA could also act directly on somatotrope cells. Therefore, we investigated the effect of oral glucose (100 g) and lipid-heparin infusion (250 mL of a 10% lipid solution + 2,500 U heparin) on the GH response to a maximal dose (2 micrograms/kg intravenously [IV]) of hexarelin or GHRH in six normal men. Hexarelin elicited a clear-cut GH response (mean +/- SEM; peak, 62.6 +/- 8.0 micrograms/L) that was higher (P < .01) than that observed after GHRH (peak, 19.8 +/- 2.4 micrograms/L). Although similar increases in plasma glucose were observed with the two peptides, oral glucose almost abolished the GH response to GHRH (peak, 5.6 +/- 0.9 micrograms/L, P < .01) while only blunting the somatotrope response to hexarelin (peak, 38.4 +/- 7.9 micrograms/L, P < .05). Similarly, lipid-heparin infusion nearly abolished the GH response to GHRH (peak, 4.9 +/- 1.0 micrograms/L, P < .01) while only blunting the somatotrope response to hexarelin (peak, 34.2 +/- 4.5 micrograms/L, P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Arginine and growth hormone-releasing hormone restore the blunted growth hormone-releasing activity of hexarelin in elderly subjects

Although both spontaneous and stimulated GH secretion undergo an age-related decline, the secretory capacity of somatotrope cells is preserved in human aging. In the present study we compared the GH responses to hexarelin, GHRH, and the combined administration of hexarelin and GHRH or arginine in young and elderly subjects. Thirteen young (24- to 30-yr-old) and 16 elderly (65- to 84-yr-old) normal males were divided into 2 groups. The first group (7 young and 8 elderly subjects) received the following as single iv injections during 3 different treatment sessions: hexarelin (2 micrograms/kg), GHRH (2 micrograms/kg), or hexarelin (2 micrograms/kg) plus GHRH (2 micrograms/kg). The second group (6 young and 8 elderly subjects) was administered single iv injections of hexarelin (2 micrograms/kg) or hexarelin (2 micrograms/kg) plus arginine (0.5 g/kg) during 2 different treatment sessions. In both groups basal IGF-I levels in the elderly were lower than those in young subjects (114.5 +/- 18.7 vs. 211.5 +/- 19.1 micrograms/L; P < 0.001). In the first group the GH response to hexarelin was greater in young compared to elderly subjects (area under the curve from 0-120 = 4849 +/- 601 vs. 2112 +/- 683 micrograms.min/L; P < 0.001). GHRH elicited a lower GH response than that induced by hexarelin in both young (1455 +/- 102 micrograms/h.L; P < 0.02) and elderly subjects (563 +/- 87 micrograms/min.L; P < 0.02). GHRH potentiated the somatotrope response to hexarelin in both young (7725 +/- 503 micrograms/min.L; P < 0.02) and elderly subjects (3895 +/- 612 micrograms/min.L; P < 0.02), but to a lesser extent in the latter (P < 0.001). In the second group, the GH response induced by hexarelin was also higher in young subjects than in elderly subjects (4819 +/- 668 vs. 1649 +/- 459 micrograms/min.L; P < 0.001). The GH response to hexarelin was potentiated by arginine in elderly (4139 +/- 1057 micrograms/min. L; P < 0.001), but not in young subjects (4743 +/- 774 micrograms/min.L). This study shows that the maximal effective dose of hexarelin releases more GH than the maximal effective dose of GHRH in both normal young and elderly subjects. The effect of hexarelin on GH secretion is age dependent, and the GH response to the combined administration of hexarelin and GHRH was significantly higher in young subjects compared to elderly subjects. Arginine does not potentiate the GH response to hexarelin in young subjects, whereas it significantly enhances it in elderly subjects.(ABSTRACT TRUNCATED AT 400 WORDS)

Growth hormone (GH)-releasing hormone secretion is stimulated by a new GH-releasing hexapeptide in sheep

The acute effect of a new GH-releasing peptide, hexarelin (1 mg, iv), on GH secretion and the mechanisms involved in its changes were investigated in conscious sheep. Peripheral GH levels and GH-releasing hormone (GHRH) and somatostatin concentrations in hypophysial portal blood were measured in six rams. An increase in jugular GH levels was observed 15 min after hexarelin injection (9.1 +/- 1.8 vs. 3.9 +/- 0.8 ng/ml; P < 0.05). This was associated with a stimulation of GHRH release into hypophysial portal blood (145.4 +/- 19.9 vs. 59.2 +/- 10.8 pg/ml; P < 0.01) without a change in somatostatin secretion. Our data indicate that GH-releasing peptide-induced GH stimulation in the sheep involves an activation of GHRH neurons in addition to the previously demonstrated direct effect on the pituitary cells.

Growth hormone-releasing activity of hexarelin in humans. A dose-response study

Hexarelin is a new hexapeptide (His-D-2-methyl-Trp-Ala-Trp-D-Phe-Lys-NH2) that stimulates the release of growth hormone both in vitro and in vivo. In this double-blind, placebo-controlled, rising-dose study we evaluated the growth hormone releasing activity of hexarelin in healthy human subjects. Twelve adult male volunteers received single intravenous boluses of 0.5, 1 and 2.micrograms.kg-1 hexarelin as well as placebo. For safety, drug doses were given in a rising-dose fashion with placebo randomly inserted into the sequence. Plasma growth hormone concentrations increased dose-dependently after the injection of the peptide, peaking at about 30 min and then decreasing to baseline values within 240 min with a half-life of about 55 min. The mean peak plasma growth hormone concentrations (Cmax) were 3.9, 26.9, 52.3, 55.0 ng.ml-1 after 0, 0.5, 1 and 2 micrograms.kg-1, respectively. The corresponding areas under the curve of growth hormone plasma levels from drug injection to 180 min (AUC0-180) were 0.135, 1.412, 2.918 and 3.695 micrograms.min.ml-1. The theoretical maximum response (Emax) and the dose that produces half of the maximum response (ED50) were estimated using logistic regression. The calculated ED50 values were 0.50 and 0.64 microgram.kg-1 for Cmax and AUC0-180, respectively. The corresponding Emaxs were 55.1 ng.ml-1 and 3936 ng.min.ml-1, thus indicating that the effect after the 2 micrograms.kg-1 dose is very close to the maximal response.(ABSTRACT TRUNCATED AT 250 WORDS)

Poly(alkylcyanoacrylate) nanocapsules: physicochemical characterization and mechanism of formation

Nanocapsules of poly(isobutylcyanoacrylate) and poly(isohexylcyanoacrylate) were prepared by addition of the monomer to an organic phase and subsequent mixing of the organic phase to an aqueous phase containing poloxamer 188, 238 or 407. Gel permeation chromatography indicated that in contrast to literature reports, polymerization occurred in the organic phase and nanocapsules were obtained by interfacial precipitation of the polymer without any significant change of the molecular weight. Addition of SO2 to the organic phase before the introduction of the monomer allowed preparation of nanocapsules with a lower molecular weight. Nanospheres were prepared in a similar way albeit using an organic phase that was completely miscible within the aqueous phase so that solid spheres were obtained. Density gradient centrifugation revealed that nanocapsules had a density intermediate between nanospheres and an emulsion prepared in the same way without addition of monomer to the organic phase. Further, the process used to prepare nanocapsules had a high yield since no oil droplets or nanospheres were obtained by this process. Zeta potential of the nanocapsules and spheres was found to be related to the molecular weight of the polymer: values as high as approximately -42 mV were obtained for low molecular weight nanocapsules (MW approximately 1000) compared to approximately -10mV for the emulsion and the high molecular weight nanocapsules (MW approximately 100,000). Surface charge of the nanocapsules and molecular weight of their polymeric wall conditioned the adsorption capacity of poloxamers. Moreover, the highest adsorption was measured with the most hydrophobic poloxamer. These observations agree with previous work conducted on hydrophobic surfaces.

Growth hormone-releasing activity of hexarelin, a new synthetic hexapeptide, after intravenous, subcutaneous, intranasal, and oral administration in man

We evaluated the GH-releasing activity of hexarelin, a new synthetic hexapeptide, after i.v. (1 and 2 micrograms/kg), sc (1.5 and 3 micrograms/kg), intranasal (20 micrograms/kg), and oral (po; 20 and 40 mg) administration to 12 healthy young volunteers. Reference treatments were i.v. saline and GH-releasing hormone (GHRH; 1 microgram/kg). GH release (mean +/- SEM) after the i.v. dose of 1 microgram/kg hexarelin [area under the curve (AUC), 3175 +/- 506 micrograms/min.L] was about 2 times higher than that induced by 1 microgram/kg GHRH (AUC, 1544 +/- 161 micrograms/min.L; P < 0.001). Hexarelin (2 micrograms/kg, i.v.) elicited a further increase in GH levels (AUC, 4422 +/- 626 micrograms/min.L) compared to the 1 microgram/kg dose. The GH response to 2 micrograms/kg hexarelin, i.v., was very reproducible (AUC, 4016 +/- 563 vs. 3959 +/- 803 micrograms/min.L). The sc administration of hexarelin produced a dose-dependent GH response (AUC, 3180 +/- 392 and 4459 +/- 566 micrograms.min.L with 1.5 and 3 micrograms/kg, respectively). Intranasal administration of 20 micrograms/kg hexarelin induced GH release (AUC, 2642 +/- 452 micrograms/min.L) similar to that caused by 1 microgram/kg, i.v. Twenty and 40 mg hexarelin, po, produced a dose-related increase in GH levels (AUC, 2278 +/- 442 and 4079 +/- 514 micrograms/min.L). Biological bioavailabilities were 77.0 +/- 10.5%, 4.8 +/- 0.9%, and 0.3 +/- 0.1% for the sc, intranasal, and po routes, respectively. This study shows that the GH response to hexarelin administered by the i.v. route has a limited variability and is superior to the response to GHRH. The GH-releasing activity appeared to be dose dependent. Thus, hexarelin could be clinically useful to stimulate GH secretion in humans.

Antarelix (EP 24332) a novel water soluble LHRH antagonist

A novel water soluble LHRH antagonist (EP 24332-Antarelix) is described. Its activity in vitro and in vivo in several animal models is given. Antarelix (Ac-D-Nal, D-Cpa, D-Pal, Ser, Tyr, D-Hci, Leu, Lys-(iPr), Pro, D-Ala-NH2) in view of its potency, modest histamine-liberating activity and high water solubility has been selected for further development.

Association of cyclosporin to isohexylcyanoacrylate nanospheres and subsequent release in human plasma in vitro

Polyisohexylcyanoacrylate nanocapsules containing cyclosporin were prepared by mixing in a 1:2 ratio an oil/ethanol solution of monomer and drug with an aqueous phase. Drug nanoencapsulation rate was controlled by its partition coefficient between the inner (organic) and outer (aqueous) phases. Thus highest encapsulation yields (88 per cent) were achieved by reducing cyclosporin solubility in the aqueous phase, i.e. by reducing ethanol concentration under reduced pressure, achieving a 3-fold volume reduction. Due to the relative insolubility of cyclosporin in water, no drug was released from the nanocapsules during storage in this injectable vehicle. Upon a 1/5 dilution in human plasma at 37 degrees C in vitro around 40 per cent of the initially encapsulated cyclosporin diffused quickly out of the capsules and an equilibrium was reached, the drug being most likely dissolved in the fatty compartment of the plasma such as lipoproteins, etc. This release mechanism is different from plain polymeric nanoparticles. Indeed, in this case the drug was released in two phases: an initial burst (around 60 per cent) of adsorbed drug as a result of the dilution, followed by a slow release (around 20 per cent over 3 h) which is likely to result from the progressive enzymatic erosion of the polymer. The initial burst was markedly more pronounced (around 80 per cent) when nanoparticle suspensions were evaporated to 1/3 of their initial volume under reduced pressure. Finally, experiments performed at 0 degree C allowed a reduction of the fraction released immediately from both types of nanospheres, probably because of a reduced solubility in plasma. In the case of nanoparticles the second phase of slow release is also inhibited at 0 degree C, in agreement with an enzymatically controlled release mechanism.

Biodegradable nanospheres containing phthalocyanines and naphthalocyanines for targeted photodynamic tumor therapy

Preparation methods of cyanoacrylic nanocapsules or nanoparticles containing phthalocyanines and naphthalocyanines are described. Nanocapsules were obtained by interfacial polymerization in an oil-in-water emulsion. Drug encapsulation efficiency depended upon drug concentration, ethanol concentration, and phthalocyanine sulfonation degree and reached 100% in some cases. Nanocapsules size ranged from 150 to 250 nm and varied with phthalocyanine sulfonation degree and pH of the aqueous phase. Nanoparticles were prepared by the addition of monomer to an aqueous phase containing hydrophilic phthalocyanine derivatives. Depending upon the pH, sizes ranged from 10 to 380 nm. Drug binding was between 75 and 80%. These new preparations could prove useful in the photodynamic treatment of tumors.

Pseudoxanthoma elasticum: similar autosomal recessive subtype in Belgian and Afrikaner families

A multidisciplinary survey of the clinical and genetic characteristics of 26 Belgian and 32 Afrikaner families with biopsy-proven pseudoxanthoma elasticum (PXE) was undertaken. The major PXE phenotype emerging from this study is very similar in both patient groups and is characterized by severe ophthalmologic manifestations with variable, mild cutaneous and vascular symptoms. In the families with more than one affected relative, segregation analysis is compatible with autosomal recessive inheritance in both groups. It is suggested that the PXE phenotype of these Belgian and Afrikaner patients is distinct from the other recognized PXE subtypes. The phenotypic resemblance in both patient groups raises the question whether a similar genetic mechanism is involved.

Mucoadhesion of hydroxypropylmethacrylate nanoparticles to rat intestinal ileal segments in vitro

The purpose of this study was to evaluate the adhesion of HPMA nanoparticles to mucus using a perfused rat ileum test system. Radiolabeled nanoparticles were prepared and deposited onto rat ileal segments in vitro. The segments were perfused and the perfusate was collected in fractions and assayed for radioactivity. Between 10 and 50% of the radioactivity was eliminated over the first 120-sec perfusion, whereas the remaining activity was firmly attached to the ileum. Among the variables tested, the time interval between nanoparticle deposition and perfusion played the major role, indicating that the mucus-nanoparticle interaction is likely to result from the diffusion of polymers into the mucus and of mucin into the polymeric matrix.

New method for the preparation of cyanoacrylic nanoparticles with improved colloidal properties

The purpose of this study was to prepare nanoparticles with a size significantly smaller than 0.1 micron. It was shown that when sulphur dioxide was dissolved in the cyanoacrylic monomer at a high concentration, subsequent anionic polymerization in an aqueous phase produced particles as small as 10 nm. Moreover, the obtained particles displayed an important negative charge which improve their stability against aggregation. Finally, nanoparticles were successfully prepared in double-distilled water, thereby avoiding the use of dextran which can induce anaphylactoid reactions.

Diffusion of rat atrial natriuretic factor in thermoreversible poloxamer gels

Concentrated poloxamer 407 solutions display a negative thermorheological behaviour, resulting in a higher viscosity at body temperature than below. This could be exploited for various controlled delivery applications including the nasal delivery of peptides. The rheology of the gel and the diffusion of ANF were studied as a function of temperature. A theory is proposed, according to which a temperature rise creates an intermicellar network resulting in a viscosity increase. The diffusion of the drug appears limited only by the presence of micelles which lengthens the diffusion pathways and is not significantly influenced by the formation of this network.

In vivo uptake of polyisobutyl cyanoacrylate nanoparticles by rat liver Kupffer, endothelial, and parenchymal cells

Polyalkyl cyanoacrylate nanoparticles were previously developed as a biodegradable, ultrafine, solid drug carrier. Distribution studies in the rat showed an intense and rapid hepatic uptake. This liver accumulation appears to represent, to a certain extent, extracellularly bound nanoparticles. During liver perfusion, 15-20% of the liver-associated nanoparticles were washed out. The cellular distribution of strongly cell-associated nanoparticles was determined. At different intervals after injection of radioactive nanoparticles to rats, the cells were isolated according to a recently developed, low-temperature procedure during which processing of the carrier was inhibited. At all tested times, a relatively intense capture by Kupffer cells in comparison with endothelial and especially parenchymal cells was observed. This distribution pattern was not influenced by the size of the nanoparticles (0.08-0.215-micron diameter). This specific interaction of nanoparticles with Kupffer cells opens possibilities for the treatment of some parasitic diseases involving this cell type.

Degradation of poly (isobutyl cyanoacrylate) nanoparticles

Poly(isobutyl cyanoacrylate) nanoparticles were prepared. They were degraded in two enzyme-free media at pH 7 and 12 in the presence of rat liver microsomes. The conventional formaldehyde-producing degradation route was studied, and showed a very low efficiency. Another pathway, consisting of ester hydrolysis, was identified and studied. In contrast to the formaldehyde pathway, ester hydrolysis was shown to be catalysed by enzymes. Finally, the release rate of adsorbed actinomycin from nanoparticles was proved to correlate exactly with the degradation rate of the polymer.

Tissue distribution of antitumor drugs associated with polyalkylcyanoacrylate nanoparticles

Polymethylcyanoacrylate nanoparticles, polyethylcyanoacrylate nanoparticles, and free 3H-dactinomycin and 3H-vinblastine were studied with emphasis on their distribution pattern in rat tissues after intravenous administration. The adsorption of cytostatic drugs to polyalkylcyanoacrylate nanoparticles can modify drug distribution in tissues. Particularly with vinblastine, modification of drug disposition is important. Data are given concerning the formation and stability of nanoparticle--drug complexes. Polyalkylcyanoacrylate nanoparticles seem to be an interesting drug carrier owing to their size, structure, degradability, and drug sorptive properties.