A study on gelatin capsule brittleness: moisture tranfer between the capsule shell and its content

Variation in moisture content of the capsule shells either due to the change of storage conditions or the moisture transfer between the capsule shell and its contents may lead to undesired physical properties, such as capsule brittleness and stickiness. DMP 504, a developmental bile-acid sequestrant, is a strongly basic anion-exchange polymer which contains randomly distributed primary, secondary, tertiary, and quaternary amine groups in their hydrochoride salt form. The alkylammonium groups which comprise this polymer form a random network containing a high level of branching and a low level of cross-linking. DMP 504 is very hygroscopic and has a tendency to gain or lose moisture with ease. The transfer of moisture from the capsule shell to DMP 504 powder contained in a hard gelatin capsule can be expected, and if a low water content of the capsule shell is achieved, the capsules become brittle and fracture easily. The sorption isotherm for DMP 504 was generated by storing the drug substance under various relative humidity conditions. After equilibrium, the moisture contents for the samples of individual isotherm points were measured by thermogravimetric analyses. This report applies the sorption-desorption moisture transfer (SDMT) model to predict the equilibrium relative humidity in a system containing DMP 504 in hard gelatin capsules and to establish target loss on drying values for DMP 504 and the capsule shell. Application of this SDMT model resulted in finding a solution to the brittleness problem. The moisture levels of capsule shells and contents for two formulations in a 12-month stability program are also reported here. Results of this study further demonstrate that the SDMT model can be used as a tool to guide the formulator to select optimal initial moisture contents for the empty capsule shell and the formulation to avoid the incidence of brittle capsule problems.

Closure of tracheoesophageal fistulas with chemotherapy and radiotherapy

In patients who have esophageal cancer with a tracheoesophageal fistula, chemotherapy and radiotherapy are usually contraindicated because it is thought to enlarge the fistula. The records of 50 patients who had esophageal cancer and received simultaneous chemotherapy and radiotherapy from January 1992 to January 1997 were evaluated in the Medical Oncology Section of the Veterans Administration Medical Center, Washington, D.C. All patients were staged radiographically and endoscopically. Four patients developed a tracheoesophageal fistula while receiving treatment. One patient developed a fistula before treatment and another patient developed a fistula after treatment. Closure of the tracheoesophageal fistulas was achieved in 4 of 5 patients who responded to therapy and in those who developed fistulas before or during therapy. One of the patients whose fistula did not close died during therapy, whereas the other who developed a fistula after therapy underwent stenting. This finding indicates that development of a tracheoesophageal fistula is not a contraindication to chemotherapy and radiotherapy, and patients who are responsive to therapy may have closure of their fistulas.

The effects of non-steroidal anti-inflammatory drugs on the disposition of methotrexate in patients with rheumatoid arthritis

We have studied the pharmacokinetics of methotrexate in patients with rheumatoid arthritis concurrently taking the most commonly used non-steroidal anti-inflammatory drugs (NSAIDs), aspirin, diclofenac, naproxen, indomethacin, and ibuprofen. The area under the curve, the total systemic clearance, the distribution volume, and the half-life of methotrexate in patients receiving concurrent NSAID therapy did not change significantly (at p < 0.05). Concurrent treatment with NSAIDs resulted in increased inter-patient variability of methotrexate concentration, possibly as a result of biochemical interactions; however, it does not appear clinically relevant. The data suggest that the NSAIDs do not significantly affect the disposition of methotrexate, contrary to some of the earlier reports.

Comparative complement activation study of polypropylene hollow fibres of two different makes in static condition

The complement activation is one of the major problems encountered in the use of extracorporeal devices. The complement-activating potential of two polypropylene hollow fibres (used in membrane oxygenator) of different make and designated as F1 and F2 was tested with time (10, 30, and 180 minutes). The fibres were brought in contact with human blood under in vitro static condition for the comparison. A direct measurement of unadsorbed concentration of the complement protein, C3, present in the liquid phase of human blood before and after the contact with polymer was made using human C3 antisera. This gave a measure of C3 adsorption on the fibres with time and probably also gave an indirect measure of C3a in the blood. IgG was also estimated using antisera of human IgG. The total protein and albumin concentration were measured to obtain an overall adsorption profile of these protein on the fibre surfaces with respect to time. The results showed that C3 adsorption was taking place mainly through the alternative pathway over and above the classical one, being more in the case of F2 than F1. SEM studies revealed poor adhesion of platelets on both fibres, though some activated platelets were also seen with slight deformation at 10 minutes and a few with prominent pseudopodia formations at a later time period on the surface of both fibres. The total protein adsorption was faster, and the surface pores of the F1 were found masked at 10 minutes observation. Later, desorption occurred making the pores visible at 180 minutes. The F2 surface examination showed a continuous deposition of protein layers with time, thereby masking the pores at 180 minutes. The present experimental finding and assessment favoured the F1 as a marginally better candidate to be considered for oxygenator development.

Nutrient composition and amino acid pattern of cowpea (Vigna unguiculata (L.) Walp, Fabaceae) grown in the Gizan area of Saudi Arabia

The proximate composition, grain protein, minerals, amino acid and sugar profiles of Vigna unguiculata (L.) Walp were analyzed. The crude protein was 23%, fat 3.40% and ash 3.60%. Amino acid analysis indicated the presence of at least 17 amino acids including most of the essential ones. The essential amino acids valine, leucine, phenylalanine and lysine were slightly higher, but sulphur-containing amino acids were lower than recommended in the WHO/FAO requirement pattern. Qualitative phytochemical screening of seeds showed fructose, alpha-glucose, beta-glucose, glycerol, manitol, inositol and some oligosaccharides, e.g. raffinose, stachyose, and verbascose. The grain contained almost similar amount of phosphorus as compared with that of Lebanese and Pakistani cultivars. Calcium was found to be lower as compared to some Indian, Pakistani and Lebanese cultivars. In general the results indicated that the legume is nutritive as staple food, feed and/or fodder.

Methotrexate in rheumatoid arthritis: a 2 year experience at a university hospital in Pakistan

In this study we report our two years experience of methotrexate (MTX) in the management of rheumatoid arthritis (RA) at the Aga Khan University Hospital, Karachi. We studied the clinical course of 124 RA patients. The mean age was 44 +/- 11 years (range 19-72) and mean duration of RA was 5 +/- 4 years (range 0.3-25). Female to male ratio was 10:2.4 (100F:24M). All of them were diagnosed according to the criteria set by American Rheumatism Association. The mean value of ESR was 60 +/- 30 (Range 3-128). Fifty one percent had severe disease (> 10 joints involved and evidence of erosions and deformities). Twenty-one patients had extra-articular manifestations. None of them had received MTX previously. Their kidney and liver functions were assessed to be normal. Patients were divided into two groups. One group (n = 92) received MTX (7.5-10 mg/week) as initial treatment, while the other group (n = 32) was given other disease modifying anti-rheumatic drugs (penicillamine, salazopyrin, gold, or chloroquine) followed by MTX. Assessment of the treatment outcome and development of any adverse reactions was carried out at 3-month interval over an average period of 1 year. Assessment of the treatment outcome in the group which received MTX as initial drug revealed the response to be excellent in 13%, good in 70%, fair in 11% and variable in 4%. In the group which received MTX as second-line of therapy, 59% of the patients had the response from good to excellent, while 25% of the patients exhibited poor to fair response. Regarding side-effects of MTX treatment, 57% exhibited none, while 35% had nausea and vomiting. Alopecia was the next common toxicity in these patients. Two individuals had abnormal liver function tests (value twice more than normal), while one developed lung fibrosis. MTX despite its adverse effects in some of the patients is still an effective, well tolerated and inexpensive disease modifying drug in RA.

POU domain transcription factor brain 4 confers pancreatic alpha-cell-specific expression of the proglucagon gene through interaction with a novel proximal promoter G1 element

The proglucagon gene is expressed in a highly restricted tissue-specific manner in the alpha cells of the pancreatic islet, the hypothalamus, and the small and large intestines. Proglucagon is processed to glucagon and glucagon-like peptides GLP-1 and -2. Glucagon is expressed in alpha cells and regulates glucose homeostasis. GLP-1 is implicated in the control of insulin secretion, food intake, and satiety signaling, and GLP-2 is implicated in regulating small-bowel growth. Cell-specific expression of the proglucagon gene is mediated by proteins that interact with the proximal G1 promoter element which contains several AT-rich domains with binding sites for homeodomain transcription factors. In an attempt to identify major homeodomain proteins involved in pancreatic alpha-cell-specific proglucagon expression, we found that the POU domain transcription factor brain 4 is abundantly expressed in proglucagon-producing islet cell lines and rat pancreatic islets. In the latter, brain 4 and glucagon immunoreactivity colocalize in the outer mantle of islets. Electrophoretic mobility shift assays with specific antisera identify brain 4 as a major constituent of nuclear proteins of glucagon-producing cells that bind to the G1 element of the proglucagon gene proximal promoter. Transcriptional transactivation experiments reveal that brain 4 is a major regulator of proglucagon gene expression by its interaction with the G1 element. The finding that a neuronal transcription factor is involved in glucagon gene transcription may explain the presence of proglucagon in certain areas of the brain as well as in pancreatic alpha cells. Further, this finding supports the idea that the neuronal properties of endodermis-derived endocrine pancreatic cells may find their basis in regulation of gene expression by neuronal transcription factors.

Intranasal absorption of the platelet glycoprotein IIb/IIIa receptor antagonist, DMP 755, and the effect of anesthesia on nasal bioavailability

Intranasal absorption and bioavailability of DMP 755, a peptidomimetic, platelet glycoprotein IIb/IIIa receptor antagonist, were examined in anesthetized and lightly sedated dogs. Nasal bioavailability was determined by measuring plasma concentrations relative to those after intravenous dosing. DMP 755 is an ester prodrug, and bioavailability reflects concentrations of the acid hydrolysis product. Nasal bioavailability in dogs anesthetized with pentobarbital was 85 +/- 4%, whereas in dogs anesthetized with the short-acting anesthetic propofol, bioavailability was 32 +/- 7%. Nasal bioavailability was greater than the reported oral bioavailability of DMP 755 in dogs, and was quite consistent. Because anesthesia affects nasal bioavailability, an effect that may depend on the absorption half-life of the test compound, a conscious or lightly sedated animal model is preferred.

Antimicrobial susceptibility of Shigella from a rural community in Bangladesh

Of the 63 Shigella strains isolated from stool cultures from 200 patients who attended a district hospital in Bangladesh with bloody diarrhoea, 37 (59%) were S. dysenteriae type 1, 25 (39%) were S. flexneri and only one (2%) was S. sonnei. Over half (54%) of the Shigella isolates came from children aged < 10 years. Most (89%) of the isolates of S. dysenteriae type 1 were resistant to ampicillin, cotrimoxazole, nalidixic acid, tetracycline and chloramphenicol. Although many (60%) of the isolates of S. flexneri were resistant to ampicillin and cotrimoxazole, only 4% of them were resistant to nalidixic acid. However, all of the S. dysenteriae and S. flexneri were sensitive to ciprofloxacin. The need for periodic monitoring to determine the resistance pattern in remote areas is emphasised.

Physical and chemical properties of DMP 504, a polyalkylammonium-based bile acid sequestrant

The purpose of this study was to characterize the physicochemical properties of DMP 504 and lay the foundation for formulation development. Thermal properties were characterized by DSC and TGA and moisture sorption and desorption by TGA. The association rate and equilibrium binding capacity of the polymer for a prototype bile acid was evaluated using cholic acid, and solid state stability was examined at 25 degrees C, 40 degrees C (with and without 5% added water), 60 degrees C, and 600 foot candles/25 degrees C. The solid state excipient compatibility of binary mixtures of DMP 504 and several commonly used pharmaceutical excipients was also evaluated. Thermal analysis of the polymer showed a glass transition temperature at approximately 95 degrees C and no melting point, indicating a highly amorphous macromolecular structure with thermal stability up to 250 degrees C. Moisture sorption and desorption isotherms at controlled humidity ranging from 11% to 97% RH did not display hysteresis. Cholic acid associated with DMP 504 extremely rapidly so that binding was essentially complete within 5 min. Scatchard analysis of the equilibrium binding of cholic acid to DMP 504 was unconventional, and indicated that the system was exhibiting positive cooperative behavior. Modeling the binding curve for a system exhibiting cooperative behavior indicated a maximum binding capacity of DMP 504 for cholic acid in phosphate buffered saline (pH 7.0) of 4.9 mumol/mg, and a cooperativity value, P, of 2.2 implying that binding of one molecule promotes the binding of additional molecules. DMP 504, a hygroscopic, amorphous cross-linked polymer with a tendency to gain or lose moisture with ease, is stable in the solid state, either drug substance alone or in presence of excipients, at normal storage temperatures and light, and under controlled conditions of humidity.

Intranasal absorption of oxymorphone

The nasal bioavailability of oxymorphone HCI was determined. Rats were surgically prepared to isolate the nasal cavity, into which a solution of oxymorphone was administered. A reference group of rats was administered oxymorphone HCl intravenously. Plasma oxymorphone concentrations were determined by HPLC. Nasal absorption was rapid, nasal bioavailability was 43%, and the iv and nasal elimination profiles were similar. Oxymorphone HCI appears to have the solubility, potency, and absorption properties required for efficient nasal delivery, which is an alternative to injections.

Effects of low-dose L-arginine on insulin-mediated vasodilatation and insulin sensitivity

The present study was carried out to evaluate the effect of a low-dose intravenous supplementation of L-arginine on insulin-mediated vasodilatation and insulin sensitivity. The study was performed in healthy subjects (n = 7) and patients with obesity (n = 9) and non-insulin-dependent diabetes mellitus (NIDDM) (n = 9). Insulin-mediated vasodilatation was measured by venous occlusion plethysmography during the insulin suppression test, evaluating insulin sensitivity. Experiments were performed twice in each subject in the presence or absence of a concomitant infusion of L-arginine (0.52 mg kg-1 min-1). L-Arginine restored the imparied insulin-mediated vasodilatation observed in obesity (22.4 +/- 4.1%, P < 0.01 vs. without L-arginine) and NIDDM (20.3 +/- 3.2%, P < 0.01 vs. without L-arginine). In healthy subjects, no effect on insulin mediated-vasodilatation was observed (24.8 +/- 3.1% vs. 21.4 +/- 3.1%). Insulin sensitivity was improved significantly (P < 0.001) in all three groups by infusion of L-arginine. No effect of L-arginine was observed on insulin, insulin-like growth factor I (IGF-I), free fatty acids (FFAs) or C-peptide levels during the insulin suppression test. Our data indicate that defective insulin-mediated vasodilatation in obesity and NIDDM can be normalized by intravenous L-arginine. Furthermore, L-arginine improves insulin sensitivity in obese patients and NIDDM patients as well as in healthy subjects, indicating a possible mechanism that is different from the restoration of insulin-mediated vasodilatation.

Sequential chemotherapy and radiotherapy for squamous cell esophageal carcinoma

A Phase II study of sequential chemotherapy with 5-fluorouracil and cisplatin followed by radiotherapy was initiated to see whether the use of two therapies sequentially could have an effect on response rate. Thirteen patients with advanced squamous cell carcinoma of the esophagus were treated with 1,000 mg/m2/day 5-fluorouracil days 1-5 continuously and 100 mg/m2 cisplatin on day 1. An average of four cycles (range, one to nine) were given every 28 days; 11 patients received more than three cycles. The radiation consisted of 60 Gy over 6-8 weeks. There was only one (8%) complete response (CR) and 11 (85%) partial responses (PRs). Restaging after radiation revealed no conversion of PR to CR. Median survival was 39 weeks (range, 6-208+). Chemotherapy alone or its use sequentially with radiotherapy is inadequate, and newer approaches are needed to to improve survival.

IGF-I inhibits burst mass of pulsatile insulin secretion at supraphysiological and low IGF-I infusion rates

Insulin-like growth factor I (IGF-I) shares structural and functional features with insulin, affects carbohydrate metabolism, and inhibits insulin secretion. Insulin secretion is pulsatile, and it is regulated by changing frequency and/or mass of secretory bursts. To examine the mechanism of IGF-I's inhibition of insulin secretion, eight healthy volunteers were studied three times. During glucose infusion (2.5 mg x kg(-1) x min(-1)) blood was sampled minutely at time 75-200 min for triplicate insulin concentration measurements by enzyme-linked immunosorbent assay (ELISA; coefficient of variation 2.1%). Time 125 min infusion of saline, low-dose IGF-I (0.025 microg x kg(-1) x min(-1)) or high-dose IGF-I (0.15 microg x kg(-1) x min(-1)) was commenced and continued until 200 min. Data were compared before (75-125 min) vs. during infusion (150-200 min). Insulin concentration time series were deconvolved, using validated pulse-detection criteria, to assess insulin secretory burst mass and frequency. During saline infusion no time effect occurred. After IGF-I infusion, serum C-peptide decreased (582 +/- 85 vs. 481 +/- 82 pM, low-dose IGF-I, P < 0.05; 539 +/- 84 vs. 427 +/- 69 pM, high-dose IGF-I, P < 0.01). Total insulin secretion rates decreased by 17 and 21%, respectively, via specific inhibition of the insulin secretory burst mass (31 +/- 8 vs. 20 +/- 4 pmol/ml, low-dose IGF-I, P = 0.06; 22 +/- 4 vs. 17 +/- 3 pmol/ml, high-dose IGF-I, P < 0.05), whereas the frequency was not affected (10.5 +/- 1.3 vs. 10.7 +/- 1.3 pulses/h, low-dose IGF-I, P = 0.85; 8.7 +/- 1.0 vs. 11.1 +/- 1.2 min/pulse, high-dose IGF-I, P = 0.15). We conclude that IGF-I inhibits pulsatile insulin secretion by specific inhibition of mass but not frequency of secretory bursts.

Effects of short-term insulin-like growth factor-I or growth hormone treatment on bone turnover, renal phosphate reabsorption and 1,25 dihydroxyvitamin D3 production in healthy man

OBJECTIVES

To find out whether insulin-like growth factor-I (IGF-I) mimics the stimulatory effects of growth hormone (GH) on bone turnover and renal tubular phosphate reabsorption.

DESIGN

Randomized, crossover study.

SETTING

University Hospital, Zürich, Switzerland.

SUBJECTS

Seven young healthy male subjects.

INTERVENTIONS

Each subject was studied three times at 2-week intervals, treated with saline 0.9% (S), IGF-I [8 micrograms kg-1 h-1] by a continuous subcutaneous infusion and finally with GH (6 U. twice daily s.c.) for 5 days.

MAIN OUTCOME MEASURES

36 h after the start of treatment, IGF-I, biochemical markers of bone turnover, calcium, calcium regulating hormones, kidney function and phosphate reabsorption were measured in serum and in 2 h urine in fasting state.

RESULTS

Serum levels of IGF-I were 26.8 +/- 7.3 (S), 119.4 +/- 11.4 (IGF-I) (P < 0.02) and 58.4 +/- 12.9 nmol L-1 (GH) (P < 0.02), respectively. Serum osteocalcin and carboxyterminal propeptide of type I collagen (PICP) as well as the urinary deoxypyridinoline/creatinine and the calcium/ creatinine ratios were all significantly higher after IGF-I (P < 0.02) or GH (P < 0.02) than after saline treatment. PTH levels did not change in response to treatment. Total albumin-corrected calcium increased only after GH treatment (P < 0.05). The free calcitriol index rose from 2.2 +/- 0.5 x 10(-5) (S) to 2.81 +/- 0.25 x 10(-5) (IGF-I) (P < 0.03) and 2.45 +/- 0.25 x 10(-5) (GH), respectively. Serum phosphate and maximal tubular reabsorption divided by glomerular filtration rate (TmP/GFR) were significantly raised by GH (P < 0.03) but not by IGF-I as compared to saline 0.9%.

CONCLUSIONS

(i) Similar to GH, IGF-I rapidly activates bone turnover. (ii) IGF-I does not mimic the effect of GH on renal phosphate reabsorption in spite of comparable effects on renal blood flow and glomerular filtration rate. (iii) IGF-I increases free calcitriol index in face of unchanged serum levels of calcium, phosphate and PTH, consistent with a direct stimulatory effect on 25-OHD-1a-hydroxylase.

Degradation kinetics of DMP 777, an elastase inhibitor

PURPOSE

The objective was to evaluate the degradation profile of the elastase inhibitor DMP 777 and lay the foundation for formulation development.

METHODS

The pKa was determined by potentiometric titration in mixed-aqueous solvents. The degradation kinetics were studied as a function of pH, buffer concentration, ionic strength, methanol concentration and temperature using a stability-indicating HPLC assay. The degradation products were identified by LC-MS, NMR, and by comparison with authentic samples.

RESULTS

The pKa for the protonated piperazine nitrogen was estimated to be 7.04. The pH-rate profile is described by specific acid-, water-, and specific base-catalyzed pathways. The pH of maximum stability is in the range of 4 to 4.5 where water is the principal catalyst in the reaction. Buffer catalysis, primary salt effects and medium effects were observed. The proposed mechanism for acid catalyzed degradation is the rarely observed AAL1 which involves alkyl-nitrogen heterolysis. The driving force for the reaction appears to lie in the stability of the benzylic carbocation. The proposed mechanism for base catalyzed degradation is BAC2 which involves beta-lactam ring opening. The beta-lactam ring of DMP 777, a monolactam, appears to be as reactive as that in benzylpenicillin in the KOH controlled region where a similar mechanism of hydrolysis should be operative. A contributing factor to this increased reactivity may lie in the reduced basicity of the beta-lactam nitrogen making it a good leaving group.

CONCLUSIONS

The degradation profile indicates that development of a solution dosage form of DMP 777 with adequate shelf-life stability at room temperature is feasible.

Hughes syndrome: a common problem in Kuwait hospitals

The objective was to study antiphospholipid antibody syndrome (APS or Hughes syndrome) in two major teaching hospitals in Kuwait. patients with suspected Hughes syndrome were investigated with tests for anticardiolipin antibodies (aCL) and lupus anticoagulants (LAC) over 1 yr. Diagnosis was considered confirmed if significant levels of either or both antibodies with no obvious cause (primary), or with systemic lupus erythematosus (SLE) or SLE-like illness (including SLE serology) (secondary) were present. Twelve (37.5%; seven females, 58%) primary and 20 (62.5%; 18 females, 90%) secondary Hughes syndrome patients were seen during this period. patients were Kuwaiti, Middle-Eastern and North-African Arabs (29). Filipinos (2) and White (1). None were from the Indian subcontinent. The main presentation was thrombosis in 75% (arterial in 25% and venous in 50%), and recurrent abortions in 50% of married women. Haematological and dermatological manifestations were limited entirely to the secondary variety, seen in 25% and 19%, respectively. Clinical manifestations were severe, leading to death in one, intensive-care management in 31% and with partial or complete warfarin resistance or brittleness in 25%. Neurological/eye and cardiac manifestations were not seen, as these patients may be attending separate speciality hospitals for these diseases in Kuwait. The approximate prevalence of this syndrome was 2.66/1000 admissions in medical wards. Projected to the total referral areas of the two hospitals, an approximate figure of 52 patients/million population/year was obtained. Hughes syndrome was a common problem among Arabs, Filipinos and possibly Whites in Kuwait. Its manifestations were severe, often requiring intensive-care management, and in one case it was fatal. Patients from the Indian subcontinent were conspicuous by their absence, despite the fact that they were well represented in all other rheumatic disease groups. Ethnic and/or geographical factors could be important in this syndrome. To the best of our knowledge, this is the first report of Hughes syndrome from the Middle East.

Solubility enhancement of a bisnaphthalimide tumoricidal agent, DMP 840, through complexation

The purpose of this research was to enhance the aqueous solubility of DMP 840 by complexation with water-soluble and nontoxic agents, and to understand the nature of the interactions involved in complex formation using nuclear magnetic resonance (1H-NMR). The solubility of DMP 840 in water, saline, acetate buffers, and cosolvent mixtures was determined by high-performance liquid chromatography, and the effect of nicotinamide and pyridoxine concentrations on the solubility of DMP 840 was examined by the phase solubility method. 1H-NMR spectra were acquired in deuterated acetate buffer at 400 MHz on a Varian Unity-400 spectrometer. The aqueous solubility of DMP 840 was sensitive to the presence of chloride and acetate anions in solution, and did not improve in the presence of cosolvents. The use of the nontoxic and water-soluble complex-forming agents nicotinamide and pyridoxine, however, resulted in a linear increase in the aqueous solubility of DMP 840 with both ligands. The solubilization appears to be due to formation of 1:1 complexes between DMP 840 and the bioorganic ligands. The complexation constants were 15.57 M-1 for the DMP 840:nicotinamide complex and 13.36 M-1 for the DMP 840:pyridoxine complex. The NMR results indicate that the interaction is a result of vertical or plane-to-plane stacking and the complexation constants were in agreement with that obtained by phase solubility. The results suggest that the aqueous solubility of a poorly water soluble drug substance such as DMP 840 can be significantly enhanced by its complexation with water-soluble and nontoxic agents.

Solubility behavior, phase transition, and structure-based nucleation inhibition of etanidazole in aqueous solutions

PURPOSE

The solubility behavior, phase transition and inhibition of the nucleation process of etanidazole were characterized.

METHODS

Solubility measurements as a function of time permitted characterization of the solubility behavior and phase transition. The precipitate from saturated solutions was isolated and characterized by differential scanning calorimetry, polarized light microscopy, x-ray powder diffraction and coulometric analysis. The physical stability of metastable systems was examined in the presence of various structure-based nucleation inhibitors.

RESULTS

Etanidazole is soluble in water with an equilibrium solubility of 68.1 mg/mL, pH 6.5 with changes in pH having virtually no effect on the solubility. Etanidazole reaches concentrations in excess of 150 mg/mL within one hour. Etanidazole solutions prepared at 150 mg/ mL contained crystals after rotating for 24 hours. The crystals were isolated and characterized as etanidazole monohydrate. the solubility of etanidazole monohydrate in water increased with time reaching an equilibrium solubility of 68 mg/mL after 24 hours. Therefore, the solubility studies were actually determining the solubility of the more stable monohydrate from of etanidazole. Etanidazole solutions at concentrations of 50, 100 and 150 mg/mL were stabilized to varying degrees with structure-based nucleation inhibitors (imidazole, ethanolamine or diethanolamine).

CONCLUSIONS

Anhydrous etanidazole undergoes a transition in aqueous solutions to the more stable monohydrate when the solubility of the monohydrate is exceeded. The physical stability of etanidazole solutions at 4 degrees C is improved following autoclaving. The addition of structure-based nucleation inhibitors effectively stabilized the metastable systems.