Oral bioavailability and intestinal absorption of candesartan cilexetil: role of naringin as P-glycoprotein inhibitor.

OBJECTIVE: The aim of the study is to explore the pharmacokinetic behavior of candesartan solid dispersions prepared by different pharmaceutical interventions using P-gp inhibitor in rabbits to validate the effectiveness of naringin as a pharmaceutical excipient in enhancing the oral delivery of lipophilic candesartan cilexetil. METHODS: Male albino rabbits (1-1.5 kg) were orally administered pure CAN suspensions and various candesartan solid dispersions (10 mg/kg) with and without naringin (15 mg/kg) and blood samples were collected at specified time points. CAN plasma samples were measured using HPLC. KEY FINDINGS: After oral dosing of pure CAN suspension, the mean AUC0-8 h was found to be 0.14 ± 0.09 µgh/ml which was increased significantly, i.e. 0.52 ± 0.13 µgh/ml with freeze-dried solid dispersions in the presence of naringin (p < 0.01). Similarly, the mean Cmax of pure CAN suspension increased from 35.81 ± 0.13 µg/ml (without naringin) to 112.23 ± 0.13 µg/ml (freeze-dried solid dispersions with naringin) (p < 0.01). A 3.7-folds increase in apparent bioavailability was noticed with freeze-dried solid dispersions with naringin as compared to free CAN suspension administered alone. CONCLUSION: These results are quite stimulating for further development of a clinically useful oral formulation of candesartan cilexetil based on P-gp inhibition using naringin, a natural flavonoid as a pharmaceutical excipient.

Corroboration of naringin effects on the intestinal absorption and pharmacokinetic behavior of candesartan cilexetil solid dispersions using in-situ rat models.

OBJECTIVE: The aim of this study was to corroborate the effects of naringin, a P-glycoprotein inhibitor, on the intestinal absorption and pharmacokinetics of candesartan (CDS) from candesartan cilexetil (CAN) solid dispersions using in-situ rat models. MATERIALS AND METHODS: Intestinal transport and absorption studies were examined by in-situ single pass perfusion and closed-loop models. We evaluated the intestinal membrane damage in the presence of naringin by measuring the release of protein and alkaline phosphatase (ALP). RESULTS AND DISCUSSION: We noticed 1.47-fold increase in Peff of CDS from freeze-dried CAN-loaded solid dispersions with naringin (15 mg/kg, w/w) when compared with freeze-dried solid dispersion without naringin using in-situ single pass intestinal perfusion model. However, no intestinal membrane damage was observed in the presence of naringin. Our findings from in-situ closed-loop pharmacokinetic studies showed 1.34-fold increase in AUC with elevated Cmax and shortened tmax for freeze-dried solid dispersion with naringin as compared to freeze-dried solid dispersion without naringin. CONCLUSION: This study demonstrated that increased solubilization (favored by freeze-dried solid dispersion) and efflux pump inhibition (using naringin), the relative bioavailability of CDS can be increased, suggesting an alternative potential for improving oral bioavailability of CAN.

Comparison of effectiveness of abrasive and enzymatic action of whitening toothpastes in removal of extrinsic stains - a clinical trial.

OBJECTIVE: To compare the effectiveness of abrasive component (perlite/calcium carbonate) and enzymatic component (papain and bromelain) of whitening toothpaste in removal of extrinsic stains. METHODS: This study is a randomized, triple blind and parallel group study in which 90 subjects aged 18-40 years were included. At baseline, stains scores were assessed by Macpherson's modification of Lobene Stain Index and subjects were randomly assigned to two groups with 45 subjects in each. Group 1 used whitening toothpaste with enzymatic action and group 2 with abrasive action. After 1 month, stain scores were assessed for the effectiveness of the two toothpastes and 2 months later to check the stain prevention efficacy. Wilcoxson's test was used to compare between baseline 1 and 2 months stain scores, and Mann-Witney U-test was applied for intragroup comparison. RESULTS: The mean baseline total stain score for the subjects allocated to the enzymatic toothpaste was 37.24 ± 2.11 which reduced to 30.77 ± 2.48 in 1 month, and for the abrasive paste, total stain reduced from 35.08 ± 2.96 to 32.89 ± 1.95. The reductions in total stain scores with both the pastes were significant compared with baseline stain scores (at 1 month Group 1, P = 0.0233 and Group 2, P = 0.0324; at 2 months, Group 1 P = 0.0356). Both the toothpastes proved to be equally good in removal of extrinsic stains; however, the enzymatic paste showed better results as compared to abrasive toothpaste. CONCLUSION: Whitening toothpaste with abrasive action and enzymatic action are equally effective in removal of extrinsic stains; however, whitening toothpaste with abrasive action needs to be used with caution.

Screening of codeine, dextromethorphan & dextropropoxyphene for their genotoxicity in Swiss albino mice.

BACKGROUND & OBJECTIVE: It is mandatory for all new drugs to be tested for their potential genotoxicity in addition to general toxicity testing. Some old drugs have not been tested adequately for their genotoxic effects as these were in use before the regulations were enforced. The present study therefore aims to explore the genotoxic potential of some commonly used opioids like codeine, dextromethorphan and dextropropoxyphene in swiss albino mice. METHODS: Therapeutic equivalent doses of codeine, dextromethorphan and dextropropoxyphene were given orally. Single dose for acute study and multiple doses (repeated every 24 h for 7 times) in additional groups of mice (n=5 in each) for subacute study. Cyclophosphamide served as positive control while normal saline as negative control. About 0.5 ml of blood was collected by retroorbital sinus for comet assay and later the mice were sacrificed to aspirate the femoral bone marrow for micronucleus test. Percentage of micronucleated polychromatic erythrocytes (MnPCE) and comet tail length were calculated in micronucleus assay and comet assay respectively, which served as markers of genotoxicity. RESULTS: Significant (P<0.001) increase in comet tail length and % MnPCE was observed in both acute and subacute studies of cyclophosphamide group, whereas codeine, dextromethorphan and dextropropoxyphene treated groups did not show any significant changes. INTERPRETATION & CONCLUSION: The results indicated that codeine, dextromethorphan and dextropropoxyphene were devoid of genotoxicity in mice.

Antidepressant activity of fosinopril, ramipril and losartan, but not of lisinopril in depressive paradigms of albino rats and mice.

Fosinopril, ramipril and losartan significantly decreased the duration (sec) of immobility in forced swim test and were comparable to amitriptyline. The duration of immobility were significantly decreased in fosinopril, ramipril and losartan in the tail suspension test and were comparable to amitriptyline. Only losartan significantly increased the rearing number of entries, time spent (sec) in open arm and in light area in comparison to control animals. Fosinopril and ramipril and not lisinopril showed significant antidepressant activity while losartan showed a significant antidepressant and anxiolytic activity. Present findings suggest that these drugs could be better antihypertensives in hypertensive patients with comorbidity like depression or anxiety.

Promotion of cutaneous wound healing by famotidine in Wistar rats.

BACKGROUND & OBJECTIVE: Drugs like famotidine, omeprazole and sucralfate which have been reported to promote the healing of gastric ulcers, may have the same effect on cutaneous wounds. Due to paucity of information in this regard, the present study was planned to investigate the effect of these drugs on resutured incision, excision and dead space wounds in Wistar rats. METHODS: Resutured incision, excision and dead space wounds were inflicted under light ether anaesthesia aseptically. Control animals received vehicle and other groups received famotidine, omeprazole and sucralfate orally for a period of 10 days in the incision and dead space wounds, whereas in excision wounds till complete closure. On the 11th day after estimating breaking strength of the resutured incision wounds, animals were sacrificed and granulation tissue removed from dead space wounds to estimate the breaking strength and hydroxyproline content. Quantification of granulation tissue and histological studies were also carried out. Wound closure rate, epithelization time and scar features were studied in the excision wound models from the day of famotidine till complete closure of the wound. RESULTS: Only famotidine significantly promoted the healing process in all the three wound models studied. Histopathological studies revealed increased collagen content and granulation tissue in famotidine treated group compared to control. INTERPRETATION & CONCLUSION: In all the three wound models studied famotidine promoted wound healing whereas omeprazole and sucralfate did not do so. The pro healing effect of famotidine needs to be explored clinically.

Development of safer molecules through chirality.

Many of the drugs currently used in medical practice are mixtures of enantiomers (racemates). Many a times, the two enantiomers differ in their pharmacokinetic and pharmacodynamic properties. Replacing existing racemates with single isomers has resulted in improved safety and/or efficacy profile of various racemates. In this review, pharmacokinetic and pharmacodynamic implications of chirality are discussed in brief, followed by an overview of some important chiral switches that have yielded safer alternatives. These include levosalbutamol, S-ketamine, levobupivacaine, S-zopiclone, levocetirizine, S-amlodipine, S-atenolol, S-metoprolol, S-omeprazole, S-pantoprazole and R-ondansetron. Few potential chiral switches under evaluation and some chiral switches that have not been successful are also discussed.

Safety evaluation of naringenin upon experimental exposure on rat gastrointestinal epithelium for novel optimal drug delivery.

OBJECTIVE: To assess the effect of naringenin on the intestinal biochemical composition, function and histology for gastrointestinal toxicity since it has not yet been adequately exploited for safety through standard assays. METHODS: Here, we describe naringenin (1 mM, 10 mM and 100 mM, respectively) or sodium deoxycholate (10 mM) effects on isolated brush border membrane from intestinal segments with single pass intestinal perfusion using lactate dehydrogenase, alkaline phosphatase and protein assays. MTT assay was used for cytotoxicity studies. Everted gut sac studies were used for evaluating the transport of nutrients across the intestinal segments. Lucifer yellow was used for paracellular permeability, followed by histological changes and surface characteristic studies of intestinal sacs. RESULTS: The results indicated no significant alterations with naringenin, although significant (p < 0.01) changes were noticed with sodium deoxycholate in the activity of the rat intestinal brush border associated enzymes such as LDH, followed by intact cell viability with marked decrease in the villi height of the intestinal segments. CONCLUSIONS: These observations indicate that naringenin was harmless upon exposure to rat gastrointestinal epithelium, clearly demonstrating the potential use of naturally occurring bioflavonoid as safe and novel pharmaceutical adjuvant in oral dosage forms as P-gp inhibitor.

Novel tablet formulation of amorphous candesartan cilexetil solid dispersions involving P-gp inhibition for optimal drug delivery: in vitro and in vivo evaluation.

OBJECTIVE: The aim of this study was to develop a novel tablet formulation of amorphous candesartan cilexetil (CAN) solid dispersion involving effective P-gp inhibition for optimal drug delivery by direct compression (DC) method. METHODS: To accomplish DC, formulation blends were evaluated for micromeritic properties. The Carr index, Hausner ratio, flow rate and cotangent of the angle α were determined. The tablets with and without naringin prepared by DC technique were evaluated for average weight, hardness, disintegration time and friability assessments. The drug release profiles were determined to study the dissolution kinetics. In vivo pharmacokinetic studies were conducted in rabbits. Accelerated stability studies were performed for tablets at 40 ± 2 °C/75% RH ± 5% for 6 months. RESULTS: FTIR studies confirmed no discoloration, liquefaction and physical interaction between naringin and drug. The results indicated that tablets prepared from naringin presented a dramatic release (82%) in 30 min with a similarity factor (76.18), which is most likely due to the amorphous nature of drug and the higher micromeritic properties of blends. Our findings noticed 1.7-fold increase in oral bioavailability of tablet prepared from naringin with mean Cmax and AUC0-12 h values as 35.81 ± 0.13 µg/mL and 0.14 ± 0.09 µg h/mL, respectively. The tablets with and without naringin prepared by DC technique were physically and chemically stable under accelerated stability conditions upon storage for 6 months. CONCLUSION: These results are attractive for further development of an oral tablet formulation of CAN through P-gp inhibition using naringin, a natural flavonoid as a pharmaceutical excipient.

Spasmolytic effect of traditional herbal formulation on guinea pig ileum.

BACKGROUND: The herbal formulation consisting of Andrographis paniculata Nees., Cassia fistula L., Foeniculum vulgare Mill. and Cuminum cyminum L. is widely used by the local traditional practitioners in rural Northern Karnataka for spasmodic abdominal pain. OBJECTIVE: The present study was undertaken to evaluate safety and spasmolytic effect of poly-herbal formulation. MATERIALS AND METHODS: Acute toxicity studies were carried out in Swiss mice, as per the Organization for Economic Co-operation and Development (OECD) guidelines. The spasmolytic activity of the formulation was studied in isolated guinea pig ileum model using histamine and acetylcholine as agonists. The data were analyzed by one-way ANOVA, followed by Dunnetts post-hoc test and P ≤ 0.05 was considered as significant. RESULTS: The formulation did not show any adverse toxic effects and found to be safe. It also showed significant (P < 0.05) relaxation in different agonist like histamine and acetylcholine-induced contractions in guinea pig ileum. CONCLUSION: Antispasmodic activity of the herbal formulation can be attributed to its atropine-like activity. The present findings, therefore, support its utility in spasmodic abdominal pain.

Enhancement of anti-inflammatory activity of aspirin by verapamil.

Verapamil in minimum therapeutic equivalent dose, failed to show anti-inflammatory activity as did sub-anti-inflammatory dose of aspirin (54 mg/kg) however, when combined with sub-antiinflammatory dose of aspirin, significant (P < 0.001) inhibition of carrageenan and cotton pellet induced inflammation was observed. The anti-inflammatory activity of this combination treatment was almost comparable to that of the anti-inflammatory dose of aspirin (200 mg/kg), as confirmed by granuloma histology. Adrenal weight in the combination treatment group was similar to that of aspirin (200 mg) treated group and was significantly lower, as compared to controls. Further, a reduced ulcer index in the animals treated with combination (aspirin + verapamil), as compared to aspirin alone (200 mg) group, suggests its therapeutic potential.

The anti-inflammatory activity of some sulphonamides in albino rats.

Clinically equivalent doses of dapsone, sulphasalasine and sulphamethizole in albino rats showed significant (P < 0.05) anti-inflammatory activity in carrageenan and cotton pellet induced inflammation. Their activity was comparable to that of aspirin (200 mg/kg) and was confirmed by granuloma histology. Further, these compounds also showed significant (P < 0.01) analgesic activity which was comparable to that of aspirin. The ulcer index for sulphamethizole was comparable to that of control animals, whereas dapsone and sulphasalazine showed significant ulcerogenicity (P < 0.01). Other sulphonamides like sulphadiazine, sulphanilamide, sulphamoxole and cotrimoxazole did not show significant anti-inflammatory and analgesic activities.

Female gonadal sex steroids potentiate the anti-convulsant activity of phenytoin sodium.

Neither estrogen (E), progesterone (P), E + P nor phenytoin could protect the rats against maximal electroshock seizure. However phenytoin administration in the E, P, or E + P pre-treated animals provided significant protection in terms of absence of hind limb extension and a decrease in the extension/flexion ratio. The results suggest that there is an existing beneficial influence of the oral contraceptives both individually and in combination on the anti-convulsant activity of phenytoin, and this needs to be further probed.

Aspirin and anticonvulsant interaction.

Aspirin (360 mg/kg, po) per se had anticonvulsant activity in MES model. No effect was observed at lower doses and in other models. Aspirin 216 mg/kg, po (a subanticonvulsant dose) protected animals, receiving subanticonvulsant doses of phenytoin, phenobarbitone and carbamazepine against MES.

Use of electromagnetic counterpoise to measure cardiac force.

To quantify the drug induced changes in cardiac force the methods in vogue use springs and strain-gauge coils, which apply counterforce to oppose cardiac force and thus stop systolic excursion of the lever. The present report pertains to a new technique based on similar principle, utilising induced electromagnetic force as a means of counterpoising in study of contractility of isolated, frog heart. The technique monitered changes in contractility produced by small doses of adrenaline, digoxin, acetylcholine and CaCl2. The plots of estimated cardiac force (in V) against doses (log-units) of the drugs could be made to reveal dose response relation.

Activity of Plumbago zeylanica Linn. root and Holoptelea integrifolia Roxb. bark pastes in acute and chronic paw inflammation in Wistar rat.

BACKGROUND: The pastes prepared from roots of Plumbago zeylanica Linn. and barks of Holoptelea integrifolia Roxb. are widely used by traditional healers for the treatment of arthritis in rural northern Karnataka. OBJECTIVE: The present study was undertaken to scientifically evaluate the safety and efficacy of traditionally used formulations in experimental animals. MATERIALS AND METHODS: The study, approved by IAEC was carried out in male Wistar rats and dermal toxicity in rabbits. Carrageenan model was used to assess effect on acute inflammation. Paw volume were measured at 1, 2, 4, and 6(th) hour postchallenge. Chronic inflammation was developed by using Complete Freund's Adjuvant (CFA). Paw volume, ankle joint circumference, and body weight were assessed on 1(st), 4(th), 8(th), 14(th), 17(th), and 21(st) day. Paste was applied once every day to the inflamed area of the paw of respective groups of animals, continuously for 14 days. STATISTICS: The data were analyzed by one way analysis of variance followed by Dunnett's post hoc test. P ≤ 0.05 was considered as significant. RESULTS: The formulations did not show any dermal toxicity and found to be safe. Both the pastes significantly (P < 0.05) suppressed, carrageenan-induced paw edema at 6(th) hour and Holoptelea integrifolia appears to be more effective than Plumbago zeylanica. Significant reduction was observed in paw volume, ankle joint circumference and animal body weight gained. CONCLUSIONS: The tested formulations (P. zeylanica root and H. integrifolia bark pastes) showed significant antiinflammatory activity. The present findings therefore support its utility in arthritic pain, inflammation and the claim of traditional practitioners.

Antiulcer activity of water soaked Glycine max L. grains in aspirin induced model of gastric ulcer in Wistar rats.

INTRODUCTION: Glycine max L. with Drakshasava, widely used by traditional healers as a formulation for the treatment of peptic ulcer in rural northern Karnataka in India, appears to be effective as assessed by patients and in our previously published research work of traditionally used formulation. AIM: The present study was undertaken to evaluate the safety and efficacy of the overnight water soaked G. max grains. This is one of the components of traditional formulation. The study, approved by Institutional Animal Ethics Committee was carried out in male Wistar rats after assessing its toxicity in mice. MATERIALS AND METHODS: Four groups of rats (n = 6 in each group) were treated with aspirin 200 mg/kg oral. In addition to aspirin control group received normal saline, standard group received 20 mg/kg omeprazole and 3(rd) and 4(th) group received G. max 250 and 500 mg/kg, respectively. All treatments were administered orally every 24 h for 7 days. After 24 hours fasting, on the 8(th) day stomach contents were aspirated under anesthesia to estimate free and total acidity. Stomachs were opened along the greater curvature to calculate ulcer index and subjected to histopathology studies. STATISTICS: The results were analyzed by one-way analysis of variance followed-by Dunnett's post hoc test. P ≤0.05 was considered as significant. RESULTS: The severity of aspirin induced ulceration was found significantly (P < 0.05) decreased in test groups compared with the control group. Free and total acidity was significantly reduced in 500 mg/kg treated group, compared with the control group and was inferior to omeprazole treated group. CONCLUSION: The grain of G. max was found to be effective against aspirin induced ulcers.

Synthesis and Pharmacological Activities of Some New 5-Substituted-2-mercapto-1,3,4-oxadiazoles.

In this study, various 5-ß-[(N-benzenesulphony/tosyl)-4-(un) substituted anilino]ethyl-2-mercapto-1,3,4-oxadiazole (4a-f), with sulphonamide moiety at the side chain have been synthesised. The structures of the newly synthesised compounds have been established on the basis of their spectral data and elemental analysis. All the compounds were screened for antimicrobial activities against Escherichia coli, Bacillus cirroflagellosus, Aspergillus niger. Colletotrichum capsici and antituberclosis activity against Mycobacterium tuberculosis H37Rv strain. Only two compounds 4b (73%) and 4e (54%), have shown moderate antituberculosis activity. All the compounds have shown moderate antiinflamatory activity and least ulcerogenecity. Most of the compounds have shown significant analgesic activity (64.20-120.72%) in comparison with the standard, Aspirin (49.39%) In the MES method, however only compound 4a, exhibited a protection of 33.33%, and others failed to protect.

Synthesis and pharmacological activities of some new 3-substituted-4-amino-5-mercapto-1,2,4-triazoles.

In this study, various 3-ß-[(N-benzenesulphonyl/tosyl)-4-(un) substituted anilino]ethyl-4-amino-5-mercapto-4(H)-1,2,4-triazoles (5a-f), with biologically active 'sulphonamide' moiety as the side chain have been prepared. The structures of the newly synthesised compounds have been established on the basis of their spectral data and elemental analysis. All the compounds were evaluated for antimicrobial activities against Escherichia coli, Bacillus cirroflagellosus, Aspergillus niger and Colletotrichum capsici. Most of the compounds investigated exhibited significant antifungal activity against Colletotrichum capsici, even greater than fluconazole, the standard used. Only two compounds 3f (59%) and 5e (67%), have shown moderate antituberculosis activity. All the triazoles exhibited moderate degree of antiinflammatory activity and least ulcerogenecity. Most of the compounds have shown significant analgesic activity (81.02-120.72%) in comparison with aspirin (49.39%). In the MES method, only compound 3e exhibited a protection of 66.66%, whereas others exhibited minimum protection of (33.33%).