Topical ophthalmic atropine in horses, pharmacokinetics and effect on intestinal motility.

BACKGROUND: Topical ophthalmic atropine sulfate is an important part of the treatment protocol in equine uveitis. Frequent administration of topical atropine may cause decreased intestinal motility and colic in horses due to systemic exposure. Atropine pharmacokinetics are unknown in horses and this knowledge gap could impede the use of atropine because of the presumed risk of unwanted effects. Additional information could therefore increase safety in atropine treatment. RESULTS: Atropine sulfate (1 mg) was administered in two experiments: In part I, atropine sulfate was administered intravenously and topically (manually as eye drops and through a subpalpebral lavage system) to six horses to document atropine disposition. Blood-samples were collected regularly and plasma was analyzed for atropine using UHPLC-MS/MS. Atropine plasma concentration was below lower limit of quantification (0.05 µg/L) within five hours, after both topical and IV administration. Atropine data were analyzed by means of population compartmental modeling and pharmacokinetic parameters estimated. The typical value was 1.7 L/kg for the steady-state volume of distribution. Total plasma clearance was 1.9 L/h‧kg. The bioavailability after administration of an ophthalmic preparation as an eye drop or topical infusion were 69 and 68%, respectively. The terminal half-life was short (0.8 h). In part II, topical ophthalmic atropine sulfate and control treatment was administered to four horses in two dosing regimens to assess the effect on gastro-intestinal motility. Borborygmi-frequency monitored by auscultation was used for estimation of gut motility. A statistically significant decrease in intestinal motility was observed after administration of 1 mg topical ophthalmic atropine sulfate every three hours compared to control, but not after administration every six hours. Clinical signs of colic were not observed under any of the treatment protocols. CONCLUSIONS: Taking the plasma exposure after topical administration into consideration, data and simulations indicate that eye drops administrated at a one and three hour interval will lead to atropine accumulation in plasma over 24 h but that a six hour interval allows total washout of atropine between two topical administrations. If constant corneal and conjunctival atropine exposure is required, a topical constant rate infusion at 5 µg/kg/24 h offers a safe alternative.

In Silico, Ex Vivo and In Vivo Studies of Roflumilast as a Potential Antidiarrheal and Antispasmodic agent: Inhibition of the PDE-4 Enzyme and Voltage-gated Ca++ ion Channels.

The aim of the present study was to evaluate the possible gut inhibitory role of the phosphodiesterase (PDE) inhibitor roflumilast. Increasing doses of roflumilast were tested against castor oil-induced diarrhea in mice, whereas the pharmacodynamics of the same effect was determined in isolated rabbit jejunum tissues. For in silico analysis, the identified PDE protein was docked with roflumilast and papaverine using the Autodock vina program from the PyRx virtual screening tool. Roflumilast protected against diarrhea significantly at 0.5 and 1.5 mg/kg doses, with 40% and 80% protection. Ex vivo findings from jejunum tissues show that roflumilast possesses an antispasmodic effect by inhibiting spontaneous contractions in a concentration-dependent manner. Roflumilast reversed carbachol (CCh, 1 µM)-mediated and potassium (K+, 80 mM)-mediated contractile responses with comparable efficacies but different potencies. The observed potency against K+ was significantly higher in comparison to CCh, similar to verapamil. Experiments were extended to further confirm the inhibitory effect on Ca++ channels. Interestingly, roflumilast deflected Ca++ concentration-response curves (CRCs) to the right with suppression of the maximum peak at both tested doses (0.001-0.003 mg/mL), similar to verapamil. The PDE-inhibitory effect was authenticated when pre-incubation of jejunum tissues with roflumilast (0.03-0.1 mg/mL) produced a leftward deflection of isoprenaline-mediated inhibitory CRCs and increased the tissue level of cAMP, similar to papaverine. This idea was further strengthened by molecular docking studies, where roflumilast exhibited a better binding affinity (-9.4 kcal/mol) with the PDE protein than the standard papaverine (-8.3 kcal/mol). In conclusion, inhibition of Ca++ channels and the PDE-4 enzyme explains the pharmacodynamics of the gut inhibitory effect of roflumilast.

Formulation and Evaluation of Fast-Disintegrating Sublingual Tablets of Atropine Sulfate: the Effect of Tablet Dimensions and Drug Load on Tablet Characteristics.

In this study, we formulated and evaluated the effects of tablet dimensions and drug load on the characteristics of atropine sulfate (AS) fast-disintegrating sublingual tablets (FDSTs). We aim to develop AS FDSTs as an alternative non-invasive and portable dosage form for the emergency treatment of organophosphate (OP) toxicity. AS autoinjector, AtroPen®, is the only self-administered dosage form available as an antidote for-out-of-hospital emergency use, but it is associated with several limitations and drawbacks. Seven FDST formulations of two tablet sizes, 150 mg (A) and 50 mg (B), and of several AS loads, 0 mg (A1, B1), 2 mg (A2, B2), 4 mg (B3), and 8 mg (B4a, B4b), were formulated and manufactured by direct compression. AS FDST characteristics were evaluated using USP and non-USP tests. Results were statistically compared at p < 0.05. All FDSTs passed the USP content uniformity and friability tests, disintegrated and released AS in ≤30 and 60 s. B1 and B2 were significantly harder than A1 and A2. Water uptake of A1 was significantly the highest. However, B1 and B2 had shorter disintegration and wetting times and higher amounts of AS dissolved than did A1 and A2 (p < 0.05). Increasing AS negatively affected FDST tensile strength (p < 0.05 for B4a) and water uptake (p < 0.05 for B3, B4a and B4b), however, without affecting AS dissolution. Formulation of AS up to 16% into smaller FDSTs was successful. Smaller FDSTs were harder and disintegrated more quickly. These AS FDSTS have the potential for further in vivo testing to evaluate their OP antidote potential.

Pharmacokinetics of Compound D, the Major Bioactive Component of Zingiber cassumunar, in Rats.

Rhizomes of Zingiber cassumunar have been used for many years in traditional Thai medicine as an anti-inflammatory agent. The major bioactive component of this plant is Compound D [E-4-(3', 4'-dimethoxyphenyl)but-3-en-1-ol], which is a strong smooth muscle relaxant, and has antihistamine and anti-inflammatory actions. There is, however, incomplete information available for the pharmacokinetics of Compound D in mammals. In this study, we examined the pharmacokinetic profiles of Compound D in male Wistar rats. A standardized extract of Z. cassumunar containing 4 % w/w Compound D was administered intravenously at 25 mg/kg or by oral gavage at 25, 75, or 250 mg/kg to Wistar rats. Blood, tissues, urine, and feces were collected from 0 to 48 h after dosing and the level of Compound D was determined by liquid chromatography-tandem mass spectrometry. The concentration of Compound D ranged from 10-100 µg/L, reached a maximum approximately 0.15 h after oral dosing. Compound D exhibited an excellent tissue to plasma ratio, ranging from 1- to 1000 in several organs at 1-4 h after oral dosing. Less than 1 % of unchanged Compound D was excreted in the urine and feces. Further studies on tissue uptake and metabolite identification are required to obtain complete pharmacokinetic information and to develop appropriate dosing strategies of Compound D and the standardized extract of Z. cassumunar.

Expression of drug transporters and drug metabolizing enzymes in the bladder urothelium in man and affinity of the bladder spasmolytic trospium chloride to transporters likely involved in its pharmacokinetics.

The cationic, water-soluble quaternary trospium chloride (TC) is incompletely absorbed from the gut and undergoes wide distribution but does not pass the blood-brain barrier. It is secreted by the kidneys, liver, and intestine. To evaluate potential transport mechanisms for TC, we measured affinity of the drug to the human uptake and efflux transporters known to be of pharmacokinetic relevance. Affinity of TC to the uptake transporters OATP1A2, -1B1, -1B3, -2B1, OCT1, -2, -3, OCTN2, NTCP, and ASBT and the efflux carriers P-gp, MRP2 and MRP3 transfected in HEK293 and MDCK2 cells was measured. To identify relevant pharmacokinetic mechanisms in the bladder urothelium, mRNA expression of multidrug transporters, drug metabolizing enzymes, and nuclear receptors, and the uptake of TC into primary human bladder urothelium (HBU) cells were measured. TC was shown to be a substrate of OATP1A2 (Km = 6.9 ± 1.3 µmol/L; Vmax = 41.6 ± 1.8 pmol/mg·min), OCT1 (Km = 106 ± 16 µmol/L; Vmax = 269 ± 18 pmol/mg·min), and P-gp (Km = 34.9 ± 7.5 µmol/L; Vmax = 105 ± 9.1 pmol/mg·min, lipovesicle assay). The genetic OATP1A2 variants *2 and *3 were loss-of-function transporters for TC. The mRNA expression analysis identified the following transporter proteins in the human urothelium: ABCB1 (P-gp), ABCC1-5 (MRP1-5), ABCG2 (BCRP), SLCO2B1 (OATP2B1), SLCO4A1 (OATP4A1), SLC22A1 (OCT1), SLC22A3 (OCT3), SLC22A4 (OCTN1), SLC22A5 (OCTN2), and SLC47A1 (MATE1). Immuno-reactive P-gp and OATP1A2 were localized to the apical cell layers. Drug metabolizing enzymes CYP3A5, -2B6, -2B7 -2E1, SULT1A1-4, UGT1A1-10, and UGT2B15, and nuclear receptors NR1H3 and NR1H4 were also expressed on mRNA level. TC was taken up into HBU cells (Km = 18.5 ± 4.8 µmol/L; Vmax = 106 ± 11.3 pmol/mg·min) by mechanisms that could be synergistically inhibited by naringin (IC50 = 10.8 (8.4; 13.8) µmol/L) and verapamil (IC50 = 4.6 (2.8; 7.5) µmol/L), inhibitors of OATP1A2 and OCT1, respectively. Affinity of TC to OCT1 and P-glycoprotein may be the reason for incomplete oral absorption, wide distribution into liver and kidneys, and substantial intestinal and renal secretions. Absence of brain distribution may result from affinity to P-gp and a low affinity to OATP1A2. The human urothelium expresses many drug transporters and drug metabolizing enzymes that may interact with TC and other drugs eliminated into the urine.

Characterization of in vitro ADME properties of diosgenin and dioscin from Dioscorea villosa.

Dioscorea villosa (wild yam) is native to North America and has been widely used as a natural alternative for estrogen replacement therapy to improve women's health as well as to treat inflammation, muscle spasm, and asthma. Diosgenin and dioscin (glycoside form of diosgenin) are reported to be the pharmacologically active compounds. Despite the reports of significant pharmacological properties of dioscin and diosgenin in conditions related to inflammation, cancer, diabetes, and gastrointestinal ailments, no reports are available on ADME properties of these compounds. This study was carried out to determine ADME properties of diosgenin and dioscin and their effects on major drug metabolizing enzymes (CYP 3A4, 2D6, 2C9, and 1A2). The stability was determined in simulated gastric and intestinal fluids (SGF, pH 1.2 and SIF, pH 6.8), and intestinal transport was evaluated in Caco-2 model. Phase I and phase II metabolic stability was determined in human liver microsomes and S9 fractions, respectively. Quantitative analysis of dioscin and diosgenin was performed by UPLC-MS system. Dioscin degraded up to 28.3 % in SGF and 12.4 % in SIF, which could be accounted for by its conversion to diosgenin (24.2 %. in SGF and 2.4 % in SIF). The depletion of diosgenin in SGF and SIF was < 10 %. Diosgenin was stable in HLM but disappeared in S9 fraction with a half-life of 11.3 min. In contrast, dioscin was stable in both HLM and S9 fractions. Dioscin showed higher permeability across Caco-2 monolayer with no significant efflux, while diosgenin was subjected to efflux mediated by P-glycoprotein. Diosgenin and dioscin inhibited CYP3A4 with IC50 values of 17 and 33 µM, respectively, while other CYP enzymes were not affected. In conclusion, dioscin showed better intestinal permeability. Conversion of dioscin to diosgenin was observed in both gastric and intestinal fluids. No phase I metabolism was detected for both compounds. The disappearance of diosgenin in S9 fraction indicated phase II metabolism.

Shenfushu granule and atropine attenuate microvasculature loss in rat models with 5/6 nephrectomy.

OBJECTIVE: To investigate the effect of Shenfushu granule (SFSG) and atropine treatment on microvessels of the kidney and intestine after chronic renal failure (CRF) induced by 5/6 nephrectomy. METHODS: Sprague Dawley rats were randomly divided into a sham group, a model group, an SFSG group, and an SFSG + atropine group. SFSG was administered daily 1 week after inducing CRF. Rats were sacrificed at the end of the eighth week. Urinary protein and stool and serum urea nitrogen (UN) and creatinine (Cr) levels were assessed. Hematoxylin and eosin and periodic acid-Schiff staining of the kidney and examination of the vascular endothelial growth factor (VEGF) and microvessel density (MVD) levels in kidney and intestine were performed. RESULTS: The Cr and UN levels were significantly increased in blood and stool of the model group. SFSG significantly improved renal function, and the protective effects were further enhanced with the addition of atropine. Glomerular sclerosis, tubulointerstitial fibrosis, and microvessel loss were observed in CRF rats, and these pathological changes were ameliorated in the two treatment groups (p < 0.05), especially in the SFSG + atropine group. The expression of VEGF and MVD was decreased in the CRF rats compared with the sham group. SFSG treatment increased the expression of these proteins and reversed the degree of microvessel loss, glomerular sclerosis, and tubulointerstitial fibrosis (p < 0.05). Co-treatment with atropine enhanced these effects. CONCLUSIONS: SFSG alleviated renal function, upregulated the expression of VEGF and MVD in the kidney and intestine, and attenuated the degree of microvessel loss, glomerular sclerosis, and tubulointerstitial fibrosis in the early stages of CRF in rats, and addition of atropine enhanced these effects.

Effect of Vemurafenib on the Pharmacokinetics of a Single Dose of Tizanidine (a CYP1A2 Substrate) in Patients With BRAFV600 Mutation-Positive Malignancies.

This phase 1 open-label, multicenter, 3-period, fixed-sequence study evaluated the effect of multiple doses of vemurafenib on the pharmacokinetics of 1 dose of tizanidine, a probe CYP1A2 substrate, in patients with BRAFV600 mutation-positive metastatic malignancy. Patients received 1 dose of tizanidine 2 mg on day 1 (period A), vemurafenib 960 mg twice daily on days 2-21 (period B), and 1 dose of tizanidine 2 mg and vemurafenib 960 mg twice daily on day 22 (period C). Log-transformed area under the concentration-time curve (AUC) and maximum plasma concentration (Cmax ) values for tizanidine in 16 patients were compared between periods A (tizanidine alone) and C (tizanidine plus vemurafenib) using an analysis of variance model. Multiple doses of vemurafenib increased plasma exposure of 1 dose of tizanidine, with geometric mean ratios (period C/period A) for Cmax , AUCinf , and AUClast of 2.15 (90%CI, 1.71-2.71), 4.22 (90%CI, 3.37-5.28), and 4.74 (90%CI, 3.55-6.33), respectively; 90%CIs were all outside predefined limits for lack of drug-drug interaction (0.82-1.22). This study confirmed vemurafenib as a moderate inhibitor of CYP1A2 in vivo, with a statistically significant drug-drug interaction with tizanidine. Caution should be exercised when dosing vemurafenib concurrently with CYP1A2 substrates.

Dual radiotracer analysis of cholinergic neuronal changes in prediabetic mouse pancreas.

BACKGROUND: Pancreatic neuronal changes associated with beta cell loss in type 1 diabetes mellitus are complex, involving, in part, parasympathetic mechanisms to compensate for preclinical hyperglycemia. The parasympathetic neurotransmitter acetylcholine (ACh) mediates insulin release via M3 muscarinic receptors on islet beta cells. The vesicular ACh transporter (VAChT) receptor has been shown to be a useful marker of cholinergic activity in vivo. The positron emission tomography (PET) radiotracer (+)-4-[(18)F]fluorobenzyltrozamicol ([(18)F]FBT) binds to the VAChT receptor on presynaptic cholinergic neurons and can be quantified by PET. The compound 4-diphenylacetoxy-N-methylpiperidine (4-DAMP), available in a tritiated form, binds to M3 muscarinic receptors on beta cells and is a potential target for assessing pancreatic beta cell mass. In this study, we investigate the feasibility of dual radiotracer analysis in identifying neurofunctional changes that may signify type 1 diabetes mellitus in its early preclinical state. METHODS: Ex vivo determinations of pancreatic uptake were performed in prediabetic nonobese diabetic mice and controls after intravenous injection of [(18)F]FBT or 4-[(3)H]DAMP. Beta cell loss in prediabetic mice was confirmed using immunohistochemical methods. RESULTS: [(18)F]FBT uptake was significantly higher in prediabetic pancreata than controls: 3.22 +/- 0.81 and 2.51 +/- 1.04, respectively (P < 0.03). 4-[(3)H]DAMP uptake was significantly lower in prediabetic pancreata than controls: 0.612 +/- 0.161 and 0.968 +/- 0.364, respectively (P = 0.01). CONCLUSIONS: These data suggest that a combination of radiotracer imaging agents that bind to neuronal elements intimately involved in insulin production may be an effective method of evaluating changes associated with early beta cell loss using PET.

Ventilatory effects of low-dose paraoxon result from central muscarinic effects.

Paraoxon induces respiratory toxicity. Atropine completely reversed parathion- and paraoxon-induced respiratory toxicity. The aim of this study was to assess the peripheral or central origin of ventilatory effects of low-dose paraoxon. Male Sprague-Dawley rats were given paraoxon 0.215 mg/kg subcutaneously and treated with either atropine (10 mg/kg sc) or ascending doses of methylatropine of 5.42 (equimolar to that of atropine), 54.2, and 542 mg/kg administered subcutaneously 30 min after paraoxon. Ventilation at rest was assessed using whole-body plethysmography and rat temperature using infra-red telemetry. Results are expressed as mean+/-SE. Statistical analysis used two-way ANOVA for repeated measurements. Paraoxon induced a significant decrease in temperature 30 min after injection lasting the 90 min of the study period. This effect was partially corrected by atropine, but not by methylatropine whatever the dose. Paraoxon induced a decrease in respiratory rate resulting from an increase in expiratory time associated with an increase in tidal volume. Atropine completely reversed the ventilatory effects of low-dose paraoxon while the equimolar dose of methylatropine had no significant effects. The 54.2 and 542 mg/kg doses of methylatropine had no significant effects. Atropine crosses the blood-brain barrier and reverses peripheral and central muscarinic effects. In contrast, methylatropine does not cross the blood-brain barrier. Atropine completely reversed the ventilatory effects of low-dose paraoxon, while methylatropine had no significant effects at doses up to 100-fold the equimolar dose of atropine. We conclude that the ventilatory effects of low-dose paraoxon are mediated by disrupted muscarinic signaling in the central nervous system.

Disposition and antimuscarinic effects of the urinary bladder spasmolytics propiverine: influence of dosage forms and circadian-time rhythms.

Propiverine extended release is expected to be better tolerated compared to immediate release tablets because of slower drug release and reduced formation of active metabolites in the colon. CYP3A4 and ABCC2, the major variables in pharmacokinetics of propiverine, are less expressed in the colon. Therefore, disposition and pharmacodynamics of propiverine were measured in a double-blind, double-dummy, crossover study with administration of 15 mg immediate release 3 times daily for 7 days compared to 45 mg extended release once daily for 7 days in 24 healthy subjects. Twelve subjects also received 15 mg propiverine intravenously. Serum and urine propiverine levels were measured repeatedly following oral administration on day 7 for up to 72 hours and correlated to duodenal expression of CYP3A4, ABCB1, and ABCC2. Propiverine immediate release 3 times daily was not different to extended release once daily in areas under the serum concentration-time curve (0-24 hours) and peak-trough fluctuation. The areas under the serum concentration-time curve of propiverine immediate release was circadian-time-dependent, with the lowest values during the night. Disposition of intravenous propiverine and propiverine immediate release administered in the night was influenced by intestinal expression of ABCC2. We concluded that oral absorption of propiverine is site-dependent and influenced by dosage form and circadian-time-dependent elimination processes.

Estimation of the impact of noncompliance on pharmacokinetics: an analysis of the influence of dosing regimens.

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT: Patient compliance is better with formulations that require less frequent dosing than with formulations that require more frequent dosing. Intramuscular risperidone and long-acting oxybutynin are two examples of medicines reformulated for less frequent dosing. However, it is not clear whether better compliance with less frequent dosing regimens translates to improved therapeutic outcome. WHAT THIS STUDY ADDS: At equivalent daily doses and typical patterns of compliance, fortnightly intramuscular depot administrations of risperidone provide better pharmacokinetic coverage than once-daily oral dosing. Once-daily dosing of oxybutynin is no better at maintaining pharmacokinetic exposure than twice-daily dosing at half strength. The use of simulated compliance data as input to pharmacokinetic models is useful to assess the impact of noncompliance on internal drug exposure. AIMS: To determine whether, for oxybutynin and risperidone, drug exposure is better with less frequent dosing regimens than with regimens that require more frequent dosing. METHODS: Pharmacokinetic models of oxybutynin (5 mg twice-daily and 10 mg once-daily) and risperidone (2 mg once-daily orally and 25 mg fortnightly intramuscular injection) were developed. Simulations of multiple doses were performed by use of stochastic models of dose-taking compliance and clinic visit attendance. RESULTS: At therapeutic concentrations and with typical patterns of noncompliance, intramuscular injections of risperidone resulted in a 41% (SD 12%) greater pharmacokinetic coverage than the oral dose, 76% (SD 10%) vs. 35% (SD 7%). No discernable differences were evident between once- and twice-daily formulations of oxybutynin, 29.2% (SD 10%) vs. 29.0% (SD 13%). CONCLUSIONS: For equivalent doses for each drug, the longer acting preparation of risperidone, but not oxybutynin, is pharmacokinetically more forgiving of noncompliance than the shorter acting counterparts. Further analysis is required to confirm whether these observations are valid clinically.

Oral bioavailability and enterohepatic recirculation of otilonium bromide in rats.

This study was conducted to examine the oral bioavailability and the possibility of enterohepatic recirculation of otilonium bromide in rats. A sensitive LC/MS/MS assay (LLOQ 0.5 ng/mL) was developed for the determination of otilonium and applied to i.v. and oral administration studies in bile duct cannulated (BDC) and non-BDC rats. After i.v. injection to BDC rats (1 mg/ kg as otilonium), average t(1/2), CL, Vz and AUC were 7.9 +/- 1.9 h, 8.7 +/- 3.1 mL/min/kg, 5.7 +/- 1.4 L/kg and 2,088 +/- 676 ng h/mL, respectively, and these values were comparable to those found in non-BDC rats. The percentages of i.v. dose excreted unchanged in bile and urine in BDC rats were 11.6 +/- 3.0 and 3.1 +/- 0.7%, respectively. Upon oral administration to non-BDC rats (20 mg/kg as otilonium), t(1/2), Cmax, Tmax and AUC were 6.4 +/- 1.3 h, 182.8 +/- 44.6 ng/mL, 1.9 +/- 1.6 h and 579 +/- 113 ng h/mL, respectively. The absolute oral bioavailability was low (1.1%), while the drug was preferentially distributed to gastrointestinal tissues. A secondary peak was observed in the serum concentration-time profiles in non-BDC rats following both i.v. and oral administration, indicating that otilonium bromide was subject to enterohepatic recirculation.

A Novel Ileocolonic Release Peppermint Oil Capsule for Treatment of Irritable Bowel Syndrome: A Phase I Study in Healthy Volunteers.

INTRODUCTION: Peppermint oil (PO) has been shown to reduce abdominal pain in patients with irritable bowel syndrome (IBS). PO is assumed to induce intestinal smooth muscle relaxation and desensitization of nociceptive nerve afferents. To increase colonic PO concentration, an ileocolonic release peppermint oil (IC-PO) capsule has been developed. The aim of this study was to compare pharmacokinetic parameters of the currently available small intestinal release PO (SI-PO) and the novel IC-PO. METHODS: In this randomized, double-blind, crossover study, subjects received 182 mg of either SI-PO or IC-PO in a crossover design with a washout period of more than 14 days. Blood samples were collected to determine menthol glucuronide concentrations. RESULTS: Eight healthy volunteers (50% female, median age 22) were included. The time to reach the maximum concentration (Tmax) of IC-PO was significantly longer compared to SI-PO with a median (IQR) of 360 (360-405) versus 180 (120-180) min. The lag time (Tlag) was significantly longer with a median (IQR) of 225 (204-284) for IC-PO compared to 37 (6-65) min for SI-PO. The areas under the menthol glucuronide plasma concentration-time curves were significantly smaller with a median (IQR) of 2331 µg h/L (2006-2510) for IC-PO compared to 2623 µg h/L (2471-2920) for SI-PO. No significant differences were found in peak concentrations and elimination half-lives. CONCLUSION: IC-PO has a significantly delayed peak menthol glucuronide concentration and Tlag, both pointing to the release of PO in the more distal part of the intestine. This may enhance therapeutic efficacy as it results in increased exposure of colonic mucosal afferents to the PO. A randomized controlled trial investigating the efficacy of SI and IC-PO in IBS is currently ongoing. TRIAL REGISTRATION: ClinicalTrials.gov identifier, NCT02291445, EudraCT database 2014-004195-32.

Pharmacokinetics and pharmacodynamics of once-daily controlled-release oxybutynin and immediate-release oxybutynin.

Oxybutynin is used to treat patients with urinary urgency, frequency, and urge incontinence. In this 2-way, multiple-dose, crossover study, the pharmacokinetics and pharmacodynamics of once-daily controlled-release oxybutynin were compared with immediate-release oxybutynin. Eighteen healthy male volunteers received one 15-mg controlled-release oxybutynin tablet once daily for 5 days or one 5-mg immediate-release oxybutynin tablet every 8 hours for 5 days. The washout period between treatments was > or =7 days. The mean steady-state AUC for oxybutynin following controlled-release oxybutynin treatment was higher (73.0 ng.h/mL) than following immediate-release oxybutynin treatment (53.6 ng.h/mL) (P = .0001). The mean C(max) was lower for controlled-release oxybutynin (5.7 ng/mL) than for immediate-release oxybutynin (7.5 ng/mL) (P = .0051), with a smaller fluctuation in oxybutynin plasma concentration for controlled-release oxybutynin (135.6%) than for immediate-release oxybutynin (319.3%) (P = .0001). Mean stimulated saliva output was greater for controlled-release oxybutynin, and mean dry mouth severity was less than immediate-release oxybutynin.

Olanzapine treatment decreases the density of muscarinic M2 receptors in the dorsal vagal complex of rats.

In this study, we investigated the effects of antipsychotic drugs, olanzapine and haloperidol, on the density of the muscarinic M2 receptors in the dorsal vagal complex (DVC) and hypoglossal nucleus (HN). Female Sprague Dawley rats were treated with olanzapine, haloperidol or vehicle (control) for 1 (short-term) or 12 weeks (long-term). Quantitative autoradiography was used to investigate the M2 receptor density in the DVC and HN using a muscarinic antagonist [(3)H] AF-DX384. Olanzapine, but not haloperidol, treatment induced a significant decrease in the binding density of M2 receptors in the DVC compared to control groups. Although the HN showed a higher density of [(3)H] AF-DX384 binding than the DVC, treatment with both olanzapine and haloperidol did not induce any significant changes in [(3)H] AF-DX384 binding in the HN. These results suggest that olanzapine-induced body weight gain may be associated with functional changes in the muscarinic neurotransmission in the DVC.

Determination of propiverine and its metabolites in rat samples by liquid chromatography-tandem mass spectrometry.

A liquid chromatography-tandem mass spectrometric (LC-MS-MS) method was developed and validated for the determination of the anticholinergic and antimuscarinc drug propiverine and eight of its metabolites in serum, urine, faeces and different tissue samples of rats. Samples containing propiverine and its metabolites in serum and urine and in the supernatants of faeces and tissue homogenates were extracted and cleaned up using an automated solid phase extraction (SPE) method. An external calibration was used. The analytes were measured employing the multiple reaction monitoring mode (MRM). A sufficient response over the range of 10-1000 ng/ml was demonstrated. The lower limit of quantification of the nine substances was 10 ng/ml. The presented method is suitable for pharmacokinetic or toxicokinetic studies. To look for additional unknown metabolites, the LC-MS-MS system operated in the precursor ion mode using typical product ions of propiverine and of its metabolites. With the help of the chromatographic behaviour and typical fragment ions of the unknown metabolites, it was possible to elucidate their structure. Five until now unknown metabolites were found in the urine and faeces samples. However, without reference substances, a quantification of these analytes was not possible.

A simple sample preparation with HPLC-UV method for estimation of tiropramide from plasma: application to bioequivalence study.

A simple, rapid and selective method was developed for estimation of tiropramide from human plasma. The method involves extracting the tiropramide with n-hexane using diphenhydramine hydrochloride as internal standard. Chromatographic separation was carried out on a reversed phase C(18) column using mixture of water and acetonitrile as mobile phase with UV detection set at 230 nm. The retention time of internal standard and tiropramide were 5.6+/-0.2 and 8.3+/-0.3 min, respectively. The method was validated and found to be linear in the range of 10-200 ng/ml. The co-efficient of variation for intra-day and inter-day accuracy and precision was less than 12.8%. The mean recovery was found to be 89%. An open, randomized, two-treatment, two period, single dose crossover, bioequivalence study in 12 fasting, healthy, male, volunteers was conducted. After dosing, serial blood samples were collected for the period of 12 h. Various pharmacokinetic parameters including AUC(0-t), AUC(0-infinity), C(max), T(max), T(1/2), and elimination rate constant (K(el)) were determined from plasma concentration of both formulations. Log transformed values were compared by analysis of variance (ANOVA) followed by classical 90% confidence interval for C(max), AUC(0-t) and AUC(0-infinity) and was found to be within the range. These results indicated that the analytical method was linear, precise and accurate. Test and reference formulation were found to be bioequivalent.

Transdermal oxybutynin: a review.

Overactive bladder is a common and disabling problem. The mainstay of pharmacological treatment is with oral anticholinergic drugs. Anticholinergic side effects are common and include dry mouth and constipation. Compliance is limited by these side effects. Transdermal administration of oxybutynin has been shown to be as effective as oral treatment while minimising the anticholinergic side effects. Skin reactions occur frequently, necessitating changes of application site. Despite this, the preparation is a useful element in the armamentarium to treat overactive bladder. It is likely to be particularly useful in those in whom side effects of oral medication are intolerable or in whom oral administration of drug is not possible. Here, the pharmacokinetics, pharmacodynamics, efficacy and safety of transdermal oxybutynin are reviewed.

Cholinergic receptor subtypes in the olfactory bulbectomy model of depression.

The connection between smoking and depression, the antidepressant actions of nicotine and the targeting of nicotinic acetylcholine receptors (nAChRs) by monoamine re-uptake inhibitors all point to a potential role of nAChRs in the etiology and/or symptomatology of depression. In the current study, we evaluated nAChR subtypes in brain regions of rats subjected to olfactory bulbectomy (OBX), a standard animal model that recapitulates many of the behavioral and neurochemical alterations thought to underlie human depression. Comparisons were made both to sham-operated controls and unoperated animals. OBX led to upregulation of cerebrocortical alpha4beta2 nAChRs and downregulation of striatal alpha7 nAChRs as compared to either the sham-operated or unoperated groups. Striatal alpha4beta2 nAChRs were also downregulated but the sham surgery by itself produced a partial effect, masking the contribution of the OBX lesion. In agreement with earlier studies, we also found downregulation of muscarinic AChRs (both m1 and m2 subtypes) in the striatum when comparing the OBX group to sham-operated controls, but because sham surgery evoked mAChR upregulation, the effect was not apparent when the OBX animals were contrasted to the unoperated group. Accordingly, caution needs to be exercised in interpreting studies of cholinergic function in the OBX model that do not include unoperated animals as an additional comparison group. Our results reinforce a relationship between depression and nAChR expression and point to the need for parallel studies in human depression that might lead to the design of novel therapies targeting specific nAChR subtypes.