Variables Affecting Delivery of Glycopyrronium Tosylate Through Human Skin In Vitro

BACKGROUND

Hyperhidrosis is a condition characterized by excessive sweating beyond what is required for normal thermal regulation. It can involve multiple body areas including the axillae, palms, soles, or craniofacial regions. Glycopyrronium tosylate (GT) is a topical anticholinergic approved by the FDA (2018) for treatment of primary axillary hyperhidrosis in patients 9 years and older.

OBJECTIVE

Gain insight into variables (anatomical sites, occlusion, exposure time) affecting GT delivery into human skin.

METHODS

Human skin from different anatomical regions (palmar, plantar, axillary, and abdominal skin) was mounted into flow-through diffusion cells (MedFlux-HT®). GT solution (2.4%) was applied at 10 mg/cm2 and the receiving fluid was collected every 2 hours, for 24 hours. GT penetration was determined using LC/MS/MS. The effect of occlusion was assessed by covering the skin with either parafilm or saran wrap, and the effect of exposure time was assessed by incubating the skin for 5, 15, or 60 minutes before washing off the GT from the surface.

RESULTS

GT delivery through palmar and plantar skin was up to 40-fold lower compared to delivery through axillary or abdominal skin. Occlusion increased GT delivery up to 10-fold. Reducing exposure time from 24 hours to either 5, 15, or 60 minutes, decreased GT flux by 90%. However, occlusion during these varied exposure times was able to restore GT delivery to levels found in the 24-hour exposed, non-occluded control group.

CONCLUSION

These in vitro skin penetration studies showed that skin thickness, exposure time, and occlusion substantially influenced GT delivery, potentially impacting clinical trial design. J Drugs Dermatol. 2020;19(11): doi:10.36849/JDD.2020.5062.

Anticholinergic Load and Nutritional Status in Older Individuals

OBJECTIVES

The association between anticholinergic load-based Anticholinergic Risk Scale scores and nutritional status is unclear in Japanese patients. The aim of this study was to establish whether anticholinergic load affects the nutritional status of geriatric patients in convalescent stages.

DESIGN

Retrospective longitudinal cohort study.

SETTING

Convalescent rehabilitation wards.

PARTICIPANTS

Of the 1490 patients aged ≥65 years who were discharged from convalescent rehabilitation wards between July 2010 and October 2018, 908 patients met the eligibility criteria. They were categorized according to the presence or absence of increased anticholinergic load from admission to discharge.

MEASUREMENTS

Demographic data, laboratory data, the Functional Independence Measure were analyzed between the groups. The primary outcome was Geriatric Nutritional Risk Index (GNRI) at discharge. Multiple linear regression analysis was performed to analyze the relationship between anticholinergic load and GNRI at discharge.

RESULTS

Multiple linear regression analysis after adjusting for confounding factors revealed that anticholinergic load was independently and negatively correlated with GNRI at discharge. Particularly, the use of chlorpromazine, hydroxyzine, haloperidol, metoclopramide, risperidone, etc. increased significantly from admission to discharge.

CONCLUSION

Increased anticholinergic load during hospitalization may be a predictor of nutritional status in geriatric patients.

In vitro and clinical characterization of the valved holding chamber AeroChamber Plus® Flow-Vu® for administrating tiotropium Respimat® in 1-5-year-old children with persistent asthmatic symptoms

BACKGROUND

When characterizing inhalation products, a comprehensive assessment including in vitro, pharmacokinetic (PK), and clinical data is required. We conducted a characterization of tiotropium Respimat^® when administered with AeroChamber Plus^® Flow-Vu^® anti-static valved holding chamber (test VHC) with face mask in 1-5-year-olds with persistent asthmatic symptoms.

METHODS

In vitro tiotropium dose and particle size distribution delivered into a cascade impactor were evaluated under fixed paediatric and adult flow rates between actuation and samplings. The tiotropium mass likely to reach children's lungs was assessed by tidal breathing simulations and an ADAM-III Child Model. PK exposure to tiotropium in preschool children with persistent asthmatic symptoms (using test VHC) was compared with pooled data from nine Phase 2/3 trials in older children, adolescents, and adults with symptomatic persistent asthma not using test VHC.

RESULTS

At fixed inspiratory flow rates, emitted mass and fine particle dose decreased under lower flow conditions; dose reduction was observed when Respimat^® was administered by test VHC at paediatric flow rates. In <5-year-old children, such a dose reduction is appropriate. In terms of dose per kg/body weight, in vitro-delivered dosing in children was comparable with adults. Transmission and aerosol holding properties of Respimat^® when administered with test VHC were fully sufficient for aerosol delivery to patients. At zero delay, particles <5 μm (most relevant fraction) exhibited a transfer efficacy of ≥60%. The half-time was>10 s, allowing multiple breaths. Standardized tidal inhalation resulted in an emitted mass from the test VHC of approximately one-third of labelled dose, independent of coordination and face mask use, indicating predictable tiotropium administration by test VHC with Respimat^®. Tiotropium exposure in 1-5-year-old patients using the test VHC, when adjusted by height or body surface, was comparable with that in older age groups without VHCs; no overexposure was observed. Adverse events were less frequent with tiotropium (2.5 μg, n = 20 [55.6%]; 5 μg, n = 18 [58.1%]) than placebo (n = 25 [73.5%]).

CONCLUSIONS

Our findings provide good initial evidence to suggest that tiotropium Respimat^® may be administered with AeroChamber Plus^® Flow-Vu^® VHC in 1-5-year-old patients with persistent asthmatic symptoms. To confirm the clinical efficacy and safety in these patients, additional trials are required.

CLINICAL TRIALS REGISTRY NUMBER

The trial was registered under NCT01634113 at http://www.clinicaltrials.gov.

Pharmacokinetics and pharmacodynamics of tiotropium solution and tiotropium powder in chronic obstructive pulmonary disease

The aim of the study was to characterize pharmacokinetics of tiotropium solution 5 µg compared to powder 18 µg and assess dose-dependency of tiotropium solution pharmacodynamics in comparison to placebo. In total 154 patients with chronic obstructive pulmonary disease (COPD) were included in this multicenter, randomized, double-blind within-solution (1.25, 2.5, 5 µg, and placebo), and open-label powder 18 µg, crossover study, including 4-week treatment periods. Primary end points were peak plasma concentration (Cmax,ss ), and area under the plasma concentration-time profile (AUC0-6h,ss ), both at steady state. The pharmacodynamic response was assessed by serial spirometry (forced expiratory volume in 1 second/forced vital capacity). Safety was evaluated as adverse events and by electrocardiogram/Holter. Tiotropium was rapidly absorbed with a median tmax,ss of 5-7 minutes postdosing for both devices. The gMean ratio of solution 5 µg over powder 18 µg was 81% (90% confidence interval, 73-89%) for Cmax,ss and 76% (70-82%) for AUC0-6h,ss , indicating that bioequivalence was not established. Dose ordering for bronchodilation was observed. Powder 18 µg and solution 5 µg were most effective, providing comparable bronchodilation. All treatments were well tolerated with no apparent relation to dose or device. Comparable bronchodilator efficacy to powder18 µg at lower systemic exposure supports tiotropium solution 5 µg for maintenance treatment of COPD.

Impact of drug administration route on drug delivery and distribution into the lung: an imaging mass spectrometry approach

During the last decade, significant technological improvements in mass spectrometry have had a great impact on drug discovery. The development of matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI-IMS) has set a new frontier for the study of the distribution of endogenous and exogenous molecules present within a tissue. MALDI-IMS is a surface sampling technique that allows not only the detection of multiple analytes but also gives the spatial distribution of those analytes. Active compounds for pulmonary disease need an optimal and well-studied delivery into the lungs, in order to assure distribution with greater penetration into the peripheral or the alveolar region of the lung to maximize the therapeutic effects. IMS is very useful in the field of drug discovery, showing drug delivery and distribution in the body and organs. In this study, we present a comparison between two different ways of carrying out pulmonary drug administration: inhalation of a nebulized aerosol of aqueous drug solutions and intratracheal administration, which is much simpler, not expensive and commonly used during in vivo screening. Tiotropium bromide is a long-acting anticholinergic medicine used for maintenance treatment of chronic obstructive pulmonary disease. In the present work, tiotropium was administered by nebulization and by intratracheal instillation to guinea pigs at doses able to induce significant anti-bronchoconstrictive activity. Lung samples were dissected, frozen, cryosectioned and coated with matrix (α-hydroxy-cinnamic acid). IMS analyses were performed using a MALDI-LTQ-Orbitrap XL. Using this technique we were able to compare different distributions of the drug depending on the method of administration.

Prodrugs of nonsteroidal anti-inflammatory drugs (NSAIDs), more than meets the eye: a critical review

The design and the synthesis of prodrugs for nonsteroidal anti-inflammatory drugs (NSAIDs) have been given much attention by medicinal chemists, especially in the last decade. As a therapeutic group, NSAIDs are among the most widely used prescribed and over the counter (OTC) medications. The rich literature about potential NSAID prodrugs clearly shows a shift from alkyl, aryalkyl or aryl esters with the sole role of masking the carboxylic acid group, to more elaborate conjugates that contain carefully chosen groups to serve specific purposes, such as enhancement of water solubility and dissolution, nitric oxide release, hydrogen sulfide release, antioxidant activity, anticholinergic and acetylcholinesterase inhibitory (AChEI) activity and site-specific targeting and delivery. This review will focus on NSAID prodrugs that have been designed or were, later, found to possess intrinsic pharmacological activity as an intact chemical entity. Such intrinsic activity might augment the anti-inflammatory activity of the NSAID, reduce its side effects or transform the potential therapeutic use from classical anti-inflammatory action to something else. Reports discussed in this review will be those of NO-NSAIDs, anticholinergic and AChEI-NSAIDs, Phospho-NSAIDs and some miscellaneous agents. In most cases, this review will cover literature dealing with these NSAID prodrugs from the year 2006 and later. Older literature will be used when necessary, e.g., to explain the chemical and biological mechanisms of action.

[Investigation of pharmacokinetics of crushed imidafenacin 0.1-mg tablet after single oral administration in healthy men]

The crushing of tablets and opening of capsules should not be performed without proper care, as these actions may adversely affect the pharmaceutical release mechanisms. However, various clinical circumstances occasionally necessitate these actions. The long-term stability of the commercial formulation of imidafenacin was confirmed after crushing of tablets. For the safe administration of crushed imidafenacin tablets, we examined the pharmacokinetics of crushed imidafenacin 0. 1-mg tablet after single oral administration in healthy men. Plasma concentrations were measured in 6 male volunteers (age, 33.3 ± 10.6 years) orally administered crushed imidafenacin under fasting conditions. Imidafenacin was rapidly absorbed and plasma concentrations peaked (Cmax) at 414 ± 108 pg/ml after 1.5 h (Tmax ; median), after which the drug was rapidly eliminated with a half-life (t1/2) of 2.8 ± 0. 3 h. Area under the plasma concentration-time curve (AUC0-10) was 1,680 ± 334 pg･h/ml. There were no significant differences in Cmax, Tmax and t1/2 between the crushed and tablet medications. Thus, crushing has almost no influence on the pharmacokinetics of imidafenacin. Consequently, this study was made available as information for patients requiring crushed anticholinergic agents.

[Anticholinergic drugs in the therapy of obstructive airway diseases]

The anticholinergic effects from botanical preparations of the deadly nightshade family have been used for hundreds of years for the treatment of obstructive airway diseases. Nowadays, derivatives of the plant alkaloids with quaternary ammonium structure, ipratropium bromide and tiotropium bromide, are used, which retain the bronchodilator properties of the parent compounds but are much safer since they are poorly absorbed across biologic membranes. They are the bronchodilators of choice in the management of chronic obstructive pulmonary disease (COPD). However, ipratropium is considered a second-line agent in the treatment of asthma as the bronchodilatory effects seen with ipratropium are less than those seen with beta-adrenergic drugs. Tiotropium is only approved for use in COPD. Though, a recent study provides some evidence that this agent may be an alternative to long-acting beta agonists as an add-on therapy to inhaled glucocorticoids for asthma.

Propiverine-induced accumulation of nuclear and cytosolic protein in F344 rat kidneys: isolation and identification of the accumulating protein

Male and female F344 rats but not B6C3F1 mice exposed for 104 weeks to propiverine hydrochloride (1-methylpiperid-4-yl 2,2-diphenyl-2-(1-propoxy)acetate hydrochloride), used for treatment of patients with neurogenic detrusor overactivity (NDO) and overactive bladder (OAB), presented with an accumulation of proteins in the cytosol and nuclei of renal proximal tubule epithelial cells, yet despite this, no increased renal tumor incidence was observed. In order to provide an improved interpretation of these findings and a better basis for human health risk assessment, male and female F344 rats were exposed for 16 weeks to 1000 ppm propiverine in the diet, the accumulating protein was isolated from the kidneys via cytosolic and nuclear preparations or laser-capture microdissection and analyzed using molecular weight determination and mass spectrometry. The accumulating protein was found to be d-amino acid oxidase (DAAO), an enzyme involved in amino and fatty acid metabolism. Subsequent reanalysis of kidney homogenate and nuclear samples as well as tissue sections using western blot and DAAO-immunohistochemistry, confirmed the presence and localization of DAAO in propiverine-treated male and female F344 rats. The accumulation of DAAO only in rats, and the limited similarity of rat DAAO with other species, including humans, suggests a rat-specific mechanism underlying the drug-induced renal DAAO accumulation with little relevance for patients chronically treated with propiverine.

Study of the metabolites of bencycloquidium bromide racemate, a novel anticholinergic compound, in rat bile by liquid chromatography-tandem mass spectrometry

A sensitive and specific liquid chromatographic-electrospray ionization (ESI) tandem ion trap mass spectrometric method has been developed for identification of bencycloquidium bromide (BCQB) and its metabolites in rat bile. Six healthy rats were administrated a single dose (3.0 mg kg(-1)) of BCQB by intraperitoneal (i.p.) injection. The bile were sampled from 0 h to 24 h and purified by using a C(18) solid- phase extraction (SPE) cartridge, then the purified bile samples were separated on a reversed-phase C(18) column using acetonitrile/40 mM ammonium acetate buffer (containing 0.1% formic acid) as mobile phase at gradient elution and detected by an on-line MS(n) detector. Identification and structural elucidation of the metabolites were performed by comparing the changes in molecular weight (Deltam) and full scan MS(n) spectra with those of the parent drug. Eight metabolites (such as hydroxylated and oxidized metabolites) and the parent drug were found in rat bile. Eight metabolites of BCQB were identified and hydroxylated metabolites were the major metabolites. The metabolic pathways of BCQB in vivo are proposed for the first time.

Determination of bencycloquidium bromide, a novel anticholinergic compound, in rat tissues by liquid chromatography-electrospray ionization mass spectrometry

First, a liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) method for quantification of bencycloquidium bromide (BCQB) in rat tissue homogenates was developed and validated, which would support investigation on drug distribution into tissues in animal models. 1-ethyl-bencycloquidium bromide was used as the internal standard (IS). Sample preparation in tissue homogenates was achieved by using solid phase extraction on a 3 mL C(18)-cartridge column. Chromatographic separation was analyzed on a Hanbon Lichrospher 5-C(18) column. The mobile phase consisted of methanol-40 mM ammonium acetate buffer-formic acid (75:25:0.25, v/v/v) which was pumped at 1.0 mL min(-1). BCQB was determined using electrospray ionization in a single quadrupole mass spectrometer. LC-ESI-MS was performed in the selected ion monitoring (SIM) mode using target ions at m/z 330.2 for BCQB and m/z 344.2 for the IS. The assay was linear from 3.015 ng mL(-1) to 301.5 ng mL(-1) of BCQB in rat tissue (liver, kidney, lung, trachea, heart, spleen, stomach, intestines, brain, muscle, testicle, ovary and fat) homogenates. The lower limit of quantification (LLOQ) was 3.015 ng mL(-1) of BCQB in all tissue homogenates. Acceptable precision and accuracy were obtained for concentrations over the entire standard curve ranges for tissue homogenates. The method was used to successfully quantify BCQB in rat tissue homogenates for a tissue distribution study of BCQB in rats after intranasal administration.

Central Anticholinergic Syndrome: A Case Report

Postoperative central anticholinergic syndrome (CAS) is caused by anticholinergic medications that cross the blood-brain barrier. Medications with central anticholinergic effects block muscarinic cholinergic receptors, resulting in a wide array of symptoms. Symptoms may range from coma to a highly agitated state. CAS may be underdiagnosed because of its varying presentation and lack of awareness. Differential diagnosis for the patient presenting with abnormal neurological signs and symptoms should include CAS after the exclusion of other potential causes. This case report details the occurrence of CAS in a patient in her 20's. A review of CAS including causes, signs and symptoms, incidence, differential diagnosis, and treatment is discussed.

Use of inhaled anticholinergic agents in obstructive airway disease

In the last 2 decades, anticholinergic agents have been generally regarded as the first-choice bronchodilator therapy in the routine management of stable chronic obstructive pulmonary disease (COPD) and, to a lesser extent, asthma. Anticholinergics are particularly important bronchodilators in COPD, because the vagal tone appears to be the only reversible component of airflow limitation in COPD. The inhaled anticholinergics approved for clinical use are synthetic quaternary ammonium congeners of atropine, and include ipratropium bromide, oxitropium bromide, and tiotropium bromide. This article reviews the most current evidence for inhaled anticholinergics in obstructive airway disease and summarizes outcomes reported in randomized controlled trials.

Effects of imidafenacin (KRP-197/ONO-8025), a new anti-cholinergic agent, on muscarinic acetylcholine receptors. High affinities for M3 and M1 receptor subtypes and selectivity for urinary bladder over salivary gland

Imidafenacin (CAS 170105-16-5, KRP-197, ONO-8025) is an antagonist for the muscarinic acetylcholine (ACh) receptor currently under development for the treatment of overactive bladder. Affinities of imidafenacin and other drugs for muscarinic ACh receptor subtypes were investigated by examining inhibitory effects on ACh release in the rat urinary bladder and K+ efflux in the rat salivary gland in functional and binding assays. In the functional assay, imidafenacin had higher affnities for M3 and M1 receptors than for the M2 receptor. In contrast, metabolites of imidafenacin (M-2, M-4 and M-9) had low affinities for muscarinic ACh receptor subtypes. Darifenacin had selectivity for the M3 receptor, while propiverine, tolterodine and oxybutynin had no selectivity for muscarinic ACh receptors. In carbamylcholine (CCh)-induced contraction in the urinary bladder, imidafenacin, propiverine, tolterodine and oxybutynin had affinities similar to those for the M3 receptor in the ileum. In the binding assay for human muscarinic ACh receptor subtypes, imidafenacin had higher affinities for m3 and m1 receptors than for m2 receptor, but tolterodine had no selectivity for m1, m2 and m3 receptors. In ACh release in the urinary bladder, inhibitory effects of imidafenacin, tolterodine, oxybutynin and darifenacin seemed to be partially mediated by the M1 receptor. In ACh-induced and electrical stimulation-induced K+ efflux from the salivary gland, inhibitory effects (IC50) of imidafenacin, propiverine, tolterodine, oxybutynin and darifenacin might be closely related to those for the M3 receptor in the ileum. These results suggest that imidafenacin more strongly antagonizes cholinomimetics on M3 and M1 receptors than on the M2 receptor. Moreover, imidafenacin seems to inhibit the contraction of the bladder smooth muscle by mediating antagonism to the M3 receptor and to regulate ACh release by mediating prejunctional facilitatory M1 receptor. Imidafenacin also inhibited K+ efflux from the salivary gland mainly by mediating the M3 receptor. Therefore, imidafenacin will have higher affinities for M3 and M1 receptors and higher selectivity for the urinary bladder than for the salivary gland.

Serum anticholinergic activity and motor performance in elderly persons

BACKGROUND

Medications prescribed to elderly persons often have an anticholinergic effect, as do many commonly used over-the-counter drugs. Anticholinergic medications are known to produce psychomotor slowing, especially in older persons.

METHODS

The present study examined whether the cumulative anticholinergic load present in the serum of community volunteers was associated with decrements on tests of psychomotor performance (gait speed and simple manual response time) known to predict falls in elderly persons.

RESULTS

Serum anticholinergic activity (SAA) was relatively low in this group; however, an elevated SAA was associated with a significant slowing in both gait speed and simple response time.

CONCLUSION

Cumulative anticholinergic burden may be one of the factors contributing to an increased risk of falls in the older population.

Determination of bencycloquidium bromide in rat plasma by liquid chromatography–electrospray ionization-mass spectrometry

A liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) assay for the determination of bencycloquidium bromide (BCQB) in rat plasma was firstly developed and validated. After addition of 1-ethyl-bencycloquidium bromide as an internal standard (I.S.), the plasma samples were deproteinized with methanol and the supernatant was assayed by LC-ESI-MS. Chromatographic separation was achieved with a Hanbon Lichrospher 5-C18 column. The mobile phase consisted of methanol-40 mM ammonium acetate buffer-formic acid (75:25:0.25, v/v/v) and delivered at the flow rate of 1.0 ml/min. LC-ESI-MS was carried out on a single quadrupole mass spectrometer using electrospray ionization (ESI) and positive selected-ion monitoring (SIM). Target ions were monitored at [M](+)m/z 330.2 for BCQB and [M] (+)m/z 344.2 for I.S. Calibration curve was linear over the range of 3-1500 ng/ml. The lower limit of quantification (LLOQ) was 3.0 ng/ml. The intra- and inter-run relative standard deviations (R.S.D.%) of the assay were less than 7.1 and 12.3%, respectively. The accuracy determined at the concentrations of 3.0, 100.0, 500.0 and 1500 ng/ml for BCQB were within +/-15.0%. The established method has been applied successfully to study the pharmacokinetics of BCQB in rats after intranasal administration.

Pharmacokinetics/Pharmacodynamics Analysis of the Relationship between the in Vivo Micturition Pressure and Receptor Occupancy of (R)-Oxybutynin and Its Metabolite in Rats

To elucidate the relationships between the pharmacokinetics and pharmacological effects of oxybutynin ((R/S)-OXY), the micturition pressure and the plasma concentration profiles of (R)-OXY and (R)-N-desethyloxybutynin ((R)-DEOB), a pharmacologically active metabolite, after administration by three different routes (i.v., p.o. and transdermal) in rats were measured and analyzed using an inhibitory effect E(max) model with their in vitro pharmacological effects. The plasma exposure ratios of (R)-DEOB to (R)-OXY calculated from the AUCs were somewhat different among the routes administered. (R)-OXY and (R)-DEOB equally inhibited the acetylcholine-induced contractions in vitro. The micturition pressure, measured using the cystometric method in vivo, exhibited saturation against the dose administered. The inhibitory effect E(max) model well described the relationship between the micturition pressure and the receptor occupancy calculated from the plasma concentrations and pA(2) values and resulted in an extremely small receptor occupancy (0.206%) to exhibit half of the maximum effect. The estimated receptor occupancy profiles suggested a sufficient and long-lasting receptor occupation after transdermal administration of (R/S)-OXY, while the receptor occupancy diminished rapidly after the i.v. and p.o. administration. These data indicate that transdermal administration of (R/S)-OXY would be useful to achieve suitable pharmacological effects without excess plasma concentrations.

The development of anticholinergics in the management of COPD

Anticholinergics have been used to treat obstructive respiratory disease for many years from historical preparations of the deadly nightshade genus, to the more recent developments ofipratropium, oxitropium, and tiotropium. The medical treatment of airways obstruction has focused on achieving maximal airway function through bronchodilators. Of the two main bronchodilators, beta2-agonists are often the first treatment choice although there is evidence of equivalence and some suggestions of the superiority of anticholinergics in chronic obstructive pulmonary disease (COPD). The following review looks at the background of anticholinergics, their pharmacological properties, and the evidence for use with suggestions for their place in the treatment of COPD.

Extrapolating from animal studies to the efficacy in humans of a pretreatment combination against organophosphate poisoning

The extrapolation from animal data to therapeutic effects in humans, a basic pharmacological issue, is especially critical in studies aimed to estimate the protective efficacy of drugs against nerve agent poisoning. Such efficacy can only be predicted by extrapolation of data from animal studies to humans. In pretreatment therapy against nerve agents, careful dose determination is even more crucial than in antidotal therapy, since excessive doses may lead to adverse effects or performance decrements. The common method of comparing dose per body weight, still used in some studies, may lead to erroneous extrapolation. A different approach is based on the comparison of plasma concentrations at steady state required to obtain a given pharmacodynamic endpoint. In the present study, this approach was applied to predict the prophylactic efficacy of the anticholinergic drug caramiphen in combination with pyridostigmine in man based on animal data. In two species of large animals, dogs and monkeys, similar plasma concentrations of caramiphen (in the range of 60-100 ng/ml) conferred adequate protection against exposure to a lethal-dose of sarin (1.6-1.8 LD(50)). Pharmacokinetic studies at steady state were required to achieve the correlation between caramiphen plasma concentrations and therapeutic effects. Evaluation of total plasma clearance values was instrumental in establishing desirable plasma concentrations and minimizing the number of animals used in the study. Previous data in the literature for plasma levels of caramiphen that do not lead to overt side effects in humans (70-100 ng/ml) enabled extrapolation to expected human protection. The method can be applied to other drugs and other clinical situations, in which human studies are impossible due to ethical considerations. When similar dose response curves are obtained in at least two animal models, the extrapolation to expected therapeutic effects in humans might be considered more reliable.

Determination of thiencynonate by liquid chromatographic-mass spectrometry and its application to pharmacokinetics in rats

A sensitive and specific high-performance liquid chromatography-tandem mass spectrometry method (LC/ESI/MS) was developed and validated for the identification and quantification of the novel lead compound of anticholinergic drug thiencynonate in rat plasma. The analytes were determined using positive electrospray ionization mass spectrometry in the selected reaction ion monitoring (SRM). The chromatography separation was on BetaBasic-18 column (150 mm x 2.1 mm i.d., 3 microm). The mobile phase was composed of methanol-water (70:30, v/v), containing 0.5 per thousand formic acid, which was pumped at a flow rate of 0.2 ml/min. Phencynonate was selected as the internal standard (IS). Simultaneous MS detection of thiencynonate and IS was performed at m/z 364.4 (thiencynonate), m/z 358 (phencynonate), and the SRM of the two compounds were both at 156. Thiencynonate eluted at approximately 2.8 min, phencynonate eluted at approximately 2.9 min and no endogenous materials interfered with their measurement. Linearity was obtained over the concentration range of 1-100 ng/ml in rat plasma. The lower limit of quantification (LLOQ) was reproducible at 1 ng/ml in rat plasma. The precision measured was obtained from 2.47 to 9.28% in rat plasma. Extraction recoveries were in the range of 67.63-76.76% in plasma. This method was successfully applied to the identification and quantification of thiencynonate in pharmacokinetic studies.

Functionalized chitosan/NIPAM (HEMA) hybrid polymer networks as inserts for ocular drug delivery: synthesis, in vitro assessment, and in vivo evaluation

A series of hybrid polymeric hydrogels, prepared by the reaction of acrylic acid-functionalized chitosan with either N-isopropylacrylamide or 2-hydroxyethyl methacrylate monomers, were synthesized, pressed into minitablets, and investigated for their ability to act as controlled release vehicles for ophthalmic drug delivery. For comparison, interpolymeric complex analogues synthesized using the same monomers and pure, unfunctionalized chitosan were examined by means of an identical characterization protocol. The effects of network structure and composition upon the swelling properties, adhesion behavior, and drug release characteristics were investigated. Comparative in vitro studies employing chloramphenicol, atropine, norfloxacin, or pilocarpine informed the selection of drug-specific carrier compositions for the controlled delivery of these compounds. In addition, in vivo (rabbit model) experiments involving the delivery of pilocarpine indicated that chitosan-based hybrid polymer networks containing 2-hydroxyethyl methacrylate are useful carriers for the delivery of this therapeutic agent.

Functionalized chitosan/NIPAM (HEMA) hybrid polymer networks as inserts for ocular drug delivery: Synthesis,in vitro assessment, andin vivo evaluation

A series of hybrid polymeric hydrogels, prepared by the reaction of acrylic acid-functionalized chitosan with either N-isopropylacrylamide or 2-hydroxyethyl methacrylate monomers, were synthesized, pressed into minitablets, and investigated for their ability to act as controlled release vehicles for ophthalmic drug delivery. For comparison, interpolymeric complex analogues synthesized using the same monomers and pure, unfunctionalized chitosan were examined by means of an identical characterization protocol. The effects of network structure and composition upon the swelling properties, adhesion behavior, and drug release characteristics were investigated. Comparative in vitro studies employing chloramphenicol, atropine, norfloxacin, or pilocarpine informed the selection of drug-specific carrier compositions for the controlled delivery of these compounds. In addition, in vivo (rabbit model) experiments involving the delivery of pilocarpine indicated that chitosan-based hybrid polymer networks containing 2-hydroxyethyl methacrylate are useful carriers for the delivery of this therapeutic agent.

Trospium chloride for the treatment of overactive bladder with urge incontinence

BACKGROUND

Urinary incontinence is caused by an overactive bladder, leading to symptoms of urgency, frequency, and incontinence. Urge incontinence occurs predominantly in women as they age.

OBJECTIVES

This article reviews the current primary literature concerning the efficacy and tolerability of the anticholinergic agent trospium chloride (TCl) in the treatment of overactive bladder with symptoms of urge incontinence, urgency, and frequency. The pharmacokinetics of TCl are also reviewed.

METHODS

Pertinent articles in English were identified through a search of MEDLINE (1966-present), EMBASE Drugs & Pharmacology (1980-third quarter 2004), Current Contents/Clinical Medicine (week 42, 2003-week 41, 2004), Cochrane Database of Systematic Reviews, MICROMEDEX Healthcare Series, and International Pharmaceutical Abstracts (1970-present). The search terms were overactive bladder, urinary incontinence, trospium, randomized controlled clinical trial, oxybutynin, tolterodine, scopolamine, imipramine, desipramine, and propantheline.

RESULTS

TCl, a quaternary amine, exhibits high solubility in water but low oral bioavailability (9.6%) and poor central nervous system penetration. Approximately 80% of the absorbed fraction is renally eliminated as unchanged drug via active tubular secretion, with approximately 15% hepatically metabolized into a spiroalcohol and hydrolysis/oxidation products. In 3 placebo-controlled studies, patients who received TCl had an increase in maximum bladder filling capacity and bladder compliance, with a reduction in maximum cystometric capacity (P < 0.005); however, only 1 of these studies showed an increase in bladder compliance, with reductions in maximum detrusor pressure (P < 0.001), number of voids/d (P < or = 0.001), and incontinence episodes/d (P < or = 0.001). In another placebo-controlled study, TCl reduced the number of voids/d and incontinence episodes/d (both, P < or = 0.001). In 2 double-blind studies, TCl and oxybutynin were similarly effective in significantly increasing maximum cystometric capacity and bladder compliance, and in significantly reducing maximum detrusor pressure compared with baseline (all, P < 0.001); there were no significant differences between the 2 treatments at end point. In a third double-blind study comparing TCl and tolterodine with placebo, only TCl significantly reduced the frequency of micturitions/d (P = 0.01). Commonly reported adverse effects in patients receiving TCl included dry mouth, constipation, and headache.

CONCLUSIONS

In the 7 studies reviewed, TCl was effective and well tolerated in patients with urge incontinence caused by idiopathic detrusor muscle overactivity or neurogenic detrusor overactivity resulting from spinal cord injury. However, this agent was associated with anticholinergic adverse effects similar to those of other anticholinergic agents; careful monitoring of tolerability is required.

Pharmacokinetic and Pharmacodynamic Evaluations of the Zwitterionic Metabolite of a New Series of N-Substituted Soft Anticholinergics

PURPOSE

This study was conducted to evaluate the zwitterionic common metabolite of a novel series of N-substituted soft analogs of glycopyrrolate both as racemates and as 2R isomers.

METHODS

Activities were assessed using both in vitro (receptor binding assay, guinea pig ileum pA2 assay) and in vivo techniques (rabbit mydriatic response, rat cardiac effects). Pharmacokinetic characterizations in rats were also performed.

RESULTS

The metabolite was highly water-soluble and very stable in buffer solutions as well as in rat biological media. Following i.v. administration in rats, it was very rapidly eliminated, mainly through renal excretion with a half-life of about 10 min. Receptor binding and guinea pig ileum assays indicated this metabolite as more than 1 order of magnitude less active than its parent soft drugs or glycopyrrolate. Moderate M3/M2 muscarinic receptor subtype selectivity was observed, further reducing the likelihood of cardiac side effects. The metabolite showed to some extent mydriatic effect and protective effect against carbachol-induced bradycardia, but of much shorter durations than glycopyrrolate; it had, however, no effect on resting heart rate.

CONCLUSIONS

N-Substituted zwitterionic metabolites retain some, but only considerably reduced activity of their parent quaternary ammonium ester soft anticholinergic drugs, and they are very rapidly eliminated from the systemic circulation. They are suitable for their assigned role within the framework of inactive metabolite-based soft anticholinergic design.

Tiotropium: A Bronchodilator for Chronic Obstructive Pulmonary Disease

OBJECTIVE:

To review the scientific literature evaluating the efficacy and tolerability of tiotropium bromide, a new bronchodilator indicated for treatment of chronic obstructive pulmonary disease (COPD).

DATA SOURCES:

Articles were identified through searches of MEDLINE (1966–January 2005) using the key words tiotropium, BA 679 BR, chronic obstructive pulmonary disease, and anticholinergic agents. Additional citations were identified from bibliographies of publications cited.

STUDY SELECTION AND DATA EXTRACTION:

Experimental and observational studies of tiotropium bromide were selected. Trials of the efficacy of the drug in humans were the focus of the review.

DATA SYNTHESIS:

Tiotropium bromide is an effective bronchodilator for patients with COPD. It produces clinically important improvements in lung function, symptoms of dyspnea, quality of life, and exacerbation rates compared with placebo. In comparative studies, tiotropium does not appear to be more efficacious than salmeterol or ipratropium.

CONCLUSIONS:

Tiotropium is an effective inhaled anticholinergic agent that is recommended among preferred long-acting bronchodilators for the chronic management of moderate to very severe COPD. Although similar to ipratropium in efficacy and tolerability, it has the advantage of once-daily dosing.

Tiotropium: An inhaled anticholinergic for chronic obstructive pulmonary disease

PURPOSE

The pharmacology, pharmacokinetics, clinical efficacy, adverse effects, drug interactions, dosage and administration, and formulary considerations of tiotropium are discussed.

SUMMARY

Tiotropium, a long-acting inhaled anticholinergic, recently received approval from the Food and Drug Administration for the management of chronic obstructive pulmonary disease (COPD). In patients with COPD, increased parasympathetic nervous system activity leads to bronchoconstriction and mucus secretion. Tiotropium induces relaxation of the airway smooth muscle, as does ipratropium, but differs in receptor association and dissociation rates, allowing for once-daily administration. After inhalation, tiotropium reaches maximal plasma concentrations within five minutes, but clinical improvements in forced expiratory volume in one second (FEV(1)) are maintained over 24 hours. Clinical trials of tiotropium with placebo, ipratropium, and salmeterol have demonstrated the efficacy of tiotropium in improving FEV(1) and forced vital capacity values and health-related quality of life. The most commonly observed adverse effect is dry mouth. No increase in adverse effects was observed when tiotropium was administered concomitantly with other drugs for COPD, including sympathomimetic bronchodilators and oral and inhaled corticosteroids. The combination of tiotropium and other anticholinergics has not been studied and is not recommended. The recommended dosage of tiotropium is the inhalation of an 18-mug capsule with a HandiHaler breath-actuated inhalation device once daily.

CONCLUSION

Tiotropium appears to be at least as effective as currently available alternatives in the treatment of patients with COPD who require daily bronchodilator treatment. Its simplified dosing and tolerable adverse-effect profile can potentially lead to enhanced patient compliance.

Central nervous system safety of anticholinergic drugs for the treatment of overactive bladder in the elderly

BACKGROUND

Overactive bladder (OAB) is characterized by urgency and increased frequency of micturition, with or without urinary urge incontinence. Anticholinergic agents are important in the treatment of OAB. However, concerns have emerged about their central nervous system (CNS) safety and the associated risk of cognitive impairment.

OBJECTIVE

This article describes the CNS adverse effects of anticholinergic drugs used for the treatment of OAB, with particular emphasis on their use in the elderly. Its objective is to help physicians make optimal choices when selecting anticholinergic treatment for OAB.

METHODS

: Relevant data from the literature were identified primarily through a MEDLINE search of articles published through December 2003. The search terms included overactive bladder, central nervous system, anticholinergic, and antimuscarinic. This was not intended to be a systematic review, and articles were chosen for inclusion based on their pertinence to the focus on treatment of OAB in the elderly.

RESULTS

Several anticholinergic drugs are available for the treatment of OAB, including oxybutymn, tolterodine, trospium chloride, and propiverine (not available in the United States). Among the agents reviewed, penetration of the blood-brain barrier (as predicted by lipophilicity, polarity, and molecular size and structure) is highest for oxybutymn, lower for tolterodine, and lowest for trospium chloride; limited data are available for propiverine. The total anticholinergic drug burden may also be important in determining the potential for CNS adverse effects. The spectrum of anticholinergic CNS adverse effects ranges from drowsiness to hallucinations, severe cognitive impairment, and even coma. The immediate-release (IR) and extended-release (ER) formulations of oxybutynin have been associated with cognitive impairment. In the only published clinical trial that was identified, no significant differences in CNS adverse effects were observed between the IR and ER formulations of tolterodine. There were few clinical data on the use of propiverine in patients with OAB. Trospium chloride has shown favorable CNS tolerability in postmarketing surveillance studies.

CONCLUSION

When considering treatment choices for patients with OAB, particularly the elderly, the potential CNS adverse effects of each anticholinergic agent must be weighed against the severity of OAB symptoms.

Biotransformation of Desoxypeganine by Microsomal Enzymes of the Rabbit Liver

The biotransformation of the anticholinergic quinazoline alkaloid Desoxypeganine is studied by means of aerobic incubation with the non-induced supernatant obtained at 9000g from rabbit liver homogenates as enzyme source followed by an admixture of NADPH. The metabolites were identified by high-performance liquid chromatography, chemical ionisation mass spectrometry (LC-CI MS) and electron impact mass spectrometry (LC-EI MS) in comparison with synthetic reference compounds and typical ion fragments taken from literature data. C-oxidation of Desoxypeganine to the major metabolite Pegenone was observed as well as the hydroxylation of the alicyclic ring. The incubation mixture followed Michaelis-Menten kinetics characterised by K(m) = 5.8 x 10(-5) mol L(-1) and V(max) = 4.32 nmol Pegenone/min per mg protein or 3.37 nmol Pegenone/min per nmol CYP 450, respectively. These in vitro results demonstrate that the bioactive substance Desoxypeganine is easily oxidised to its ineffective metabolite Pegenone. This provokes a problem for correct dosage finding in formulations for the treatment of Alzheimer's disease and in the therapy of alcoholism and nicotine dependence.

Clinical pharmacokinetics of drugs used to treat urge incontinence

Urge incontinence (also known as overactive bladder) is a common form of urinary incontinence, occurring alone or as a component of mixed urinary incontinence, frequently together with stress incontinence. Because of the pathophysiology of urge incontinence, anticholinergic/antispasmodic agents form the cornerstone of therapy. Unfortunately, the pharmacological activity of these agents is not limited to the urinary tract, leading to systemic adverse effects that often promote nonadherence. Although the pharmacokinetics of flavoxate, propantheline, scopolamine, imipramine/desipramine, trospium chloride and propiverine are also reviewed here, only for oxybutynin and tolterodine are there adequate efficacy/tolerability data to support their use in urge incontinence. Oxybutynin is poorly absorbed orally (2-11% for the immediate-release tablet formulation). Controlled-release oral formulations significantly prolong the time to peak plasma concentration and reduce the degree of fluctuation around the average concentration. Significant absorption occurs after intravesical (bladder) and transdermal administration, although concentrations of the active N-desethyl metabolite are lower after transdermal compared with oral administration, possibly improving tolerability. Food has been found to significantly affect the absorption of one of the controlled-release formulations of oxybutynin, enhancing the rate of drug release. Oxybutynin is extensively metabolised, principally via N-demethylation mediated by the cytochrome P450 (CYP) 3A isozyme. The pharmacokinetics of tolterodine are dependent in large part on the pharmacogenomics of the CYP2D6 and 3A4 isozymes. In an unselected population, oral bioavailability of tolterodine ranges from 10% to 74% (mean 33%) whereas in CYP2D6 extensive metabolisers and poor metabolisers mean bioavailabilities are 26% and 91%, respectively. Tolterodine is metabolised via CYP2D6 to the active metabolite 5-hydroxymethyl-tolterodine and via CYP3A to N-dealkylated metabolites. Urinary excretion of parent compound plays a minor role in drug disposition. Drug effect is based upon the unbound concentration of the so-called 'active moiety' (sum of tolterodine + 5-hydroxymethyl-tolterodine). Terminal disposition half-lives of tolterodine and 5-hydroxymethyl-tolterodine (in CYP2D6 extensive metabolisers) are 2-3 and 3-4 hours, respectively. Coadministration of antacid essentially converts the extended-release formulation into an immediate-release formulation. Knowledge of the pharmacokinetics of these agents may improve the treatment of urge incontinence by allowing the identification of individuals at high risk for toxicity with 'usual' dosages. In addition, the use of alternative formulations (controlled-release oral, transdermal) may also facilitate adherence, not only by reducing the frequency of drug administration but also by enhancing tolerability by altering the proportions of parent compound and active metabolite in the blood.

[Tiotropium. A new anti-cholinergic agent for treatment of chronic obstructive pulmonary disease]

Tiotropium is a new anti-cholinergic drug with a long duration of action designed for maintenance treatment of chronic obstructive pulmonary disease (COPD). Tiotropium is the first drug specifically developed for the treatment of COPD, but it is also amongst the most expensive drugs used for this condition. The clinical pharmacology of tiotropium and results from published controlled clinical trials are reviewed. It is concluded that tiotropium seems suitable as a symptomatic treatment for patients with moderate to severe COPD (typically a forced expiratorical volume FEV1 < 50% of the predicted volume), who despite optimal use of short acting bronchodilators still suffer from severe symptoms.

Sensitive determination of oxybutynin and desethyloxybutynin in dog plasma by LC-ESI/MS/MS

A sensitive and selective liquid chromatographic method coupled with tandem mass spectrometry (LC-MS/MS) was developed for the quantification of oxybutynin and desethyloxybutynin in dog plasma. Diazepam was used as internal standard, with plasma sample extracted using n-hexane and back-extracted using hydrochloric acid. A centrifuged lower layer (aqueous layer) was injected into a C(18) XTerra MS column (2.1 x 30 mm(2)) with 3.5 microm particle size. The analytical column lasted for at least 500 injections. The mobile phase was composed of 90% methanol, with flow rate at 200 microl/min. The mass spectrometer was operated in positive ion mode using electrospray ionization. Nitrogen was used as the nebulizer gas and argon was used as the collision gas. Using MS/MS with multiple reaction monitoring (MRM) mode, oxybutynin and desethyloxybutynin were detected without severe interferences from plasma matrix. Oxybutynin produced a protonated precursor ion ([M+H](+)) at m/z 358 and a corresponding product ion at m/z 142. Desethyloxybutynin produced a protonated precursor ion ([M+H](+)) at m/z 330 and a corresponding product ion at m/z 96. And internal standard (diazepam) produced a protonated precursor ion ([M+H](+)) at m/z 285 and a corresponding product ion at m/z 193. Detection of oxybutynin and desethyloxybutynin in dog plasma were accurate and precise, with detection limit at 0.1 ng/ml. This method has been successfully applied to a study of oxybutynin and desethyloxybutynin in dog plasma.

New perspectives on the overactive bladder: pharmacokinetics and bioavailability

In the United States alone, approximately 17 million men and women have symptoms of overactive bladder (OAB). For many years, oxybutynin was the drug of choice for treating OAB. Although it provided effective treatment, multiple daily doses were required, and adverse events, such as dry mouth and constipation, were decided drawbacks. Controlled drug delivery systems seen in commercially available OAB formulations alter the pharmacokinetics of antimuscarinic medications in ways that maintain efficacy and allow once-daily dosing and reduction of adverse events. In the future, OAB medications will not only incorporate new chemical entities, such as the S-enantiomer of oxybutynin, but will also use novel drug delivery technologies, including transdermal patches and bladder implants.

Pharmacodynamic steady state of tiotropium in patients with chronic obstructive pulmonary disease

Tiotropium (Spiriva) is a new once-daily inhaled anticholinergic that has its effect through prolonged muscarinic (M)3 receptor antagonism. It has a clinically documented, long duration of action with once-daily dosing in chronic obstructive pulmonary disease (COPD). A single-centre, double-blind, ipratropium-controlled study was conducted in order to characterize the onset of pharmacodynamic steady state of tiotropium in patients with COPD. Thirty-one patients (25 male, six female) with a mean age of 62 yrs and a mean forced expiratory volume in one second (FEV1) of 1.13 L (38% of predicted) were randomly assigned to receive either tiotropium 18 microg once-daily from a dry-powder inhaler (HandiHaler, 20 patients), or ipratropium 40 microg four-times daily from a pressurized metered-dose inhaler (11 patients) for a period of 1 week. FEV1 and forced vital capacity (FVC) were measured 1 h prior to, and just before inhalation (mean value of the two measurements on test-day 1 was the baseline value, while on all other test days it was the trough value), and 0.5, 1, 2, 3, 4, 5, and 6 h after inhalation of the morning dose of the study drug (one capsule and two puffs) on days 1, 2, 3, and 8. Trough FEV1 following 8 days of tiotropium was 0.19 L (18%) above baseline. Approximately 90% of this increase was achieved within 24 h of the first dose (0.17 L, 16%). Trough FVC increased 0.67 L (27%) on test-day 8. Approximately 70% of the improvement was observed after two tiotropium doses (0.47 L, 19%). Achievement of FVC steady state was delayed compared to FEV1. Ipratropium performed typically with an onset of action within 30 min, a peak response between 1-2 h postdosing and a duration of action of approximately 4 h. It was concluded that forced expiratory volume in one second steady state with tiotropium is reached within 48 h, while continued improvements in forced vital capacity can be expected over or beyond the first week of therapy. The continued increases in forced vital capacity beyond 48 h suggests that maintenance bronchodilator therapy is required to achieve maximal changes in hyperinflation.

Pharmacokinetics, efficacy, and safety of intravesical formulation of oxybutynin in patients with detrusor overactivity

OBJECTIVE

To determine the pharmacokinetics of oxybutynin and its main active metabolite, N-desethyloxybutynin, after multiple dosage (5 mg/30 ml three times daily) of intravesical oxybutynin formulation. Furthermore, to determine the efficacy and safety of intravesical oxybutynin in the symptomatic relief of urge incontinence or urgency in adult patients with detrusor hyperreflexia or instability.

MATERIAL AND METHODS

Nine patients were randomly allocated to treatment with a special bladder instillation formulation of oxybutynin or placebo for two 14-day treatment periods in a double-blind, cross-over manner. The third, open study period was designed for pharmacokinetic purposes with all patients on the active drug. The pharmacokinetics was depicted by AUC0-24, Cmax, Cmin, and t(max), The efficacy was evaluated from the data collected from urinary voiding diaries and cystometries. The safety was measured by recording adverse events on questionnaires. Patients who were willing to continue with the intravesical oxybutynin treatment entered the 1-year extension part of the study.

RESULTS

Oxybutynin was absorbed from the bladder with a geometric mean Cmax of 9.4 ng/ml and AUC0-24 of 92 ng x h/ml. For N-desethyloxybutynin, the geometric mean Cmax was 14.4 ng/ml and AUC0-24 186 ng x h/ml. Elimination of the drug was protracted, as there were detectable serum concentrations of both oxybutynin and N-desethyloxybutynin even 24 hours post-dose. The mean number of toilet visits/day decreased from the baseline value of 6.9 to 5.7 during oxybutynin treatment, whereas during the placebo period the value increased to 7.4 (p = 0.022). It remained at the same decreased level during the one-year follow-up period.

CONCLUSIONS

Oxybutynin is readily absorbed from the bladder after intravesical administration. The serum concentrations of oxybutynin after single 5 mg intravesical doses are at least as high as those reported after oral drug intake, but the parent drug/metabolite ratio is much higher after intravesical administration. The elimination of oxybutynin as well as its metabolite is prolonged after intravesical administration compared with that reported after oral drug intake. The mean number of daily toilet visits decreased significantly in the oxybutynin group.

Design, pharmacokinetic, and pharmacodynamic evaluation of soft anticholinergics based on tropyl alpha-phenylcyclopentylacetate

Four new soft anticholinergic agents based on tropyl alpha-phenylcyclopentylacetate, 15a, 15b, 18a, and 18b, were designed and synthesized. Receptor binding studies on the cloned human muscarinic receptors indicated that the new soft anticholinergic agents possessed moderate potency as pKi ranged from 6.7 to 7.6. Mydriatic studies in rabbit eyes revealed that the duration of the action of the new soft anticholinergics (8.5-11.0 h) were shorter than that of atropine (about 24 h) under pharmacodynamic equivalent dose, and one of them, 18a, showed even shorter than that of tropicamide. In addition, after unilateral administration, significant dilation of pupil in the control eyes was observed with tropicamide and atropine but not with soft drugs, suggesting the systemic activity of soft drugs was minimal. With their soft nature, the new soft anticholinergics displayed much shorter protective effect against carbachol-induced bradycardia (about 30 min) than atropine (at least 60 min) in rats. In vitro and in vivo pharmacokinetic studies demonstrated that the soft anticholinergics were rapidly hydrolyzed into the corresponding inactive metabolites once they were introduced into the systemic circulation.

Intravesical oxybutynin: mode of action assessed by passive diffusion and electromotive administration with pharmacokinetics of oxybutynin and N-desethyl oxybutynin

PURPOSE

A proportion of patients with detrusor hyperreflexia who are unresponsive to oral oxybutynin often benefit from intravesical oxybutynin instillation. To our knowledge the precise mode of action of this method is obscure.

MATERIALS AND METHODS

In 12 patients with detrusor hyperreflexia who were previously unresponsive to oral and intravesical passive diffusion of 5 mg. oxybutynin we administered 5 mg. oxybutynin orally as well as increased doses of 15 mg. oxybutynin intravesically with passive diffusion and with 15 mA. associated electric current. Each administration mode per patient was associated with an 8-hour urodynamic monitoring session during which oxybutynin and N-desethyl oxybutynin plasma levels, and intravesical oxybutynin uptake were measured.

RESULTS

A dose of 5 mg. oxybutynin orally induced no urodynamic improvement with an area under the plasma concentration time curve of combined N-desethyl oxybutynin plus oxybutynin of 16,297 ng./8 hours and an area under the curve ratio of N-desethyl oxybutynin-to-oxybutynin of 11:1. Passive diffusion oxybutynin resulted in 12 mg. oxybutynin intravesical uptake and significant improvement in 3 of 8 urodynamic measurements, although the area under the curve of combined N-desethyl oxybutynin plus oxybutynin was only 2,123 ng./8 hours and the N-desethyl oxybutynin-to-oxybutynin ratio was 1.1:1.0. Electromotive administration of oxybutynin resulted in almost complete intravesical uptake of the 15 mg. dose, significant improvement in all 8 urodynamic measurements and an increased oxybutynin level versus oral and passive diffusion, although the area under the curve of combined N-desethyl oxybutynin plus oxybutynin was 4,574 ng./8 hours and the N-desethyl oxybutynin-to-oxybutynin ratio was inverted at 1.0:1.4. The oral dose of 5 mg. oxybutynin caused anticholinergic side effects in 8 of the 12 patients. Neither intravesical passive diffusion nor electromotive administration caused side effects with an uptake of 12 and 15 mg., respectively.

CONCLUSIONS

A large proportion of intravesical oxybutynin is sequestered, probably in the urothelium. Intravesical oxybutynin administration confers therapeutic benefits via localized direct action within the bladder wall.

Effect of OROS controlled-release delivery on the pharmacokinetics and pharmacodynamics of oxybutynin chloride

Aims : Dry mouth is a common side-effect seen with immediate-release oxybutynin (IR-Oxy). Ditropan XL [(Oxy-XL), a controlled-release formulation of oxybutynin chloride, is a once-daily oral dosage form that incorporates the OROS technology. Dry mouth as the pharmacodynamic measure was compared between Oxy-XL and IR-Oxy administration. The steady state stereospecific pharmacokinetics were also established for the two formulations and the kinetic-dynamic relationship of oxybutynin was examined.

METHODS

This was a randomized, repeated-dose, double-blind, two-treatment, two-period, crossover study. After a baseline assessment day, volunteers were randomly assigned to one of two treatment sequences and received 4 days of each treatment with a washout period of 7 days between treatments. The treatments were: 1) Oxy-XL 10 mg in the morning and placebo 8 h later, and 2) IR-Oxy 5 mg in the morning and again 8 h later. Volunteers assessed dry mouth severity subjectively using a 100 mm visual analogue scale, VAS (Baseline, treatment days 1 and 4) and objectively by collecting saliva (Baseline and treatment day 4) before dosing and every hour after the morning dose for approximately 16 h. Several blood samples were collected during each treatment, with frequent sampling on day 4 to analyse for plasma R- and S-oxybutynin and R- and S-desethyloxybutynin concentrations.

RESULTS

Relatively constant plasma concentrations of oxybutynin and its metabolite were seen over 24 h following Oxy-XL administration with the degree of fluctuation being much lower (P = 0.001; 66% to 81% reduction for the various analytes) than IR-Oxy. Compared with IR-Oxy, Oxy-XL yielded higher (131% and 158% for the R- and S-isomer, respectively) oxybutynin and lower (62% and 78% for the R- and S-isomer, respectively) desethyloxybutynin bioavailability, suggesting reduced first-pass metabolism. Saliva output (area under the effect curve) was significantly higher [P = 0.001; 37% (95% confidence interval: 24, 51%)] with Oxy-XL than with IR-Oxy and, accordingly, dry mouth severity (VAS) integrated over the day was significantly lower with Oxy-XL. The decrease in saliva output and the consequent increase in dry mouth severity correlated with the metabolite R-desethyloxybutynin concentration, and no apparent relationship was observed with the R-oxybutynin concentration. This suggests that the metabolite may contribute to the dry mouth. Therefore, the reduction in metabolite exposure with Oxy-XL may be a possible explanation for the observed decrease in dry mouth severity with OXY-XL compared with IR-Oxy.

CONCLUSIONS

Oxy-XL maintains relatively constant plasma drug and metabolite concentrations and minimizes first-pass metabolism of oxybutynin. The metabolite appears to contribute to dry mouth associated with oxybutynin, and following Oxy-XL metabolite exposure is reduced compared with IR-Oxy. Consequently less dry mouth was observed with Oxy-XL as compared with IR-Oxy.

Pharmacokinetic/pharmacodynamic assessment of the effects of E4031, cisapride, terfenadine and terodiline on monophasic action potential duration in dog

1. Torsades de pointes (TDP) is a potentially fatal ventricular tachycardia associated with increases in QT interval and monophasic action potential duration (MAPD). TDP is a side-effect that has led to withdrawal of several drugs from the market (e.g. terfenadine and terodiline). 2. The potential of compounds to cause TDP was evaluated by monitoring their effects on MAPD in dog. Four compounds known to increase QT interval and cause TDP were investigated: terfenadine, terodiline, cisapride and E4031. On the basis that only free drug in the systemic circulation will elicit a pharmacological response target, free concentrations in plasma were selected to mimic the free drug exposures in man. Infusion regimens were designed that rapidly achieved and maintained target-free concentrations of these drugs in plasma and data on the relationship between free concentration and changes in MAPD were obtained for these compounds. 3. These data indicate that the free ED50 in plasma for terfenadine (1.9 nM), terodiline (76 nM), cisapride (11 nM) and E4031 (1.9 nM) closely correlate with the free concentration in man causing QT effects. For compounds that have shown TDP in the clinic (terfenadine, terodiline, cisapride) there is little differentiation between the dog ED50 and the efficacious free plasma concentrations in man (< 10-fold) reflecting their limited safety margins. These data underline the need to maximize the therapeutic ratio with respect to TDP in potential development candidates and the importance of using free drug concentrations in pharmacokinetic/pharmacodynamic studies.

Supercritical fluid extraction and analysis of compounds from Clivia miniata for uterotonic activity

In this descriptive study, the superciritical fluid extract of the roots of Clivia miniata L. was tested for uterotonic activity using guinea pig uterine smooth muscle in vitro. Extraction was performed with water modified supercritical carbon dioxide at 400 atm and 80 degrees C. The uterine contractions induced by this extract were compared to those induced by the aqueous extract and found to be active at lower doses. The active compounds were isolated and the structures elucidated by spectroscopic and chromatographic techniques. Both linoleic acid and 5-hydroxymethyl-2-furancarboxaldehyde isolated from the extract were found to induce muscle contractions individually. The pharmacological mode of action of 5-hydroxymethyl-2-furancarboxaldehyde was assessed using two receptor agonists and antagonists. This compound was found to mediate its effect through cholinergic receptors.

Pharmacokinetics and tissue distribution of the anticholinergics tiotropium and ipratropium in the rat and dog

Ipratropium, a current treatment for chronic obstructive pulmonary disease (COPD) and tiotropium, a longer acting anticholinergic bronchodilator currently being developed for COPD are structurally related to atropine. In this study, the intravenous (i.v.), oral (p.o.) and intratracheal (i.tr.) single dose pharmacokinetics (PK) of tiotropium and ipratropium were determined in rat and dog. In rats, concentration-time profiles of tiotropium and ipratropium after single i.v. bolus administration of 7-8 mg kg(-1) are similar. Both drugs are highly cleared (Cl between 87 and 150 ml min(-1) kg(-1)) and extensively distributed into tissues (volume of distribution V(ss) between 3 and 15 l kg(-1)). In dogs, this holds also true for both drugs (Cl between 34 and 42 ml min(-1) kg(-1), V(ss) between 2 and 10 l kg(-1)), although different dose regimen were applied (i.v. bolus of 0.08 mg kg(-1) vs. infusion of 0.1 mg kg(-1) h(-1) for 3 h). Tiotropium plasma concentrations increased linearly in rats over a wide dose range following single i.v. administration. Both ipratropium and tiotropium showed a comparable terminal elimination half-life in rat urine (21-24 h) after single i.v. administration, which was much longer than the corresponding half-life in plasma (6-8 h). Whole body autoradiography in rats revealed a broad and rapid tissue distribution of [(14)C]tiotropium radioactivity after single i.v. administration. A comparable distribution pattern has also been reported earlier for ipratropium.

The pharmacologic profile of desloratadine: a review

Desloratadine is a new agent for the treatment of diseases such as seasonal allergic rhinitis and chronic urticaria. The pharmacologic profile of desloratadine offers particular benefits in terms of histamine H1-receptor binding potency and H1 selectivity. Desloratadine has a half-life of 21-24 h, permitting once-daily dosing. No specific cautions are required with respect to administration in renal or hepatic failure, and food or grapefruit juice have no effect on the pharmacologic parameters. No clinically relevant racial or sex variations in the disposition of desloratadine have been noted. In combination with the cytochrome P450 inhibitors, ketoconazole and erythromycin, the AUC and Cmax of desloratadine were increased to a small extent, but no clinically relevant drug accumulation occurred. With high-dose treatment (45 mg/day for 10 days), no significant adverse events were observed, despite the sustained elevation of plasma desloratadine levels. Specifically, desloratadine had no effects on the corrected QT interval (QTc) when administered alone, at high dose, or in combination with ketoconazole or erythromycin. Preclinical studies also show that desloratadine does not interfere with HERG channels or cardiac conduction parameters even at high dose. Desloratadine is nonsedating and free of antimuscarinic/anticholinergic effects in preclinical and clinical studies. Novel antiallergic and anti-inflammatory effects have also been noted with desloratadine, a fact which may be relevant to its clinical efficacy.

Intravesical electromotive administration of oxybutynin in patients with detrusor hyperreflexia unresponsive to standard anticholinergic regimens

PURPOSE

About 15% to 20% of patients with detrusor hyperreflexia do not benefit from oral oxybutynin regimens, frequently because of unpleasant side effects. Several reports indicate that intravesical oxybutynin is effective in many of these patients but there are some who still fail to respond.

MATERIALS AND METHODS

A select group of 10 adults with detrusor hyperreflexia unresponsive to standard oral and intravesical oxybutynin regimens were treated at weekly intervals with 5 mg. oxybutynin orally, or 5 mg. oxybutynin in 100 ml. intravesically for 60 minutes of passive diffusion and for 30 minutes with 5 mA. electrical current. Each treatment (plus oral placebo and 2 intravesical controls) was associated with an 8-hour, full urodynamic monitoring session, and periodic blood and bladder content sampling.

RESULTS

There was no significant objective improvement with oral or intravesical passive diffusion oxybutynin. Conversely there was significant improvement in 5 of 6 objective urodynamic measurements with intravesical electromotive oxybutynin. Plasma profiles were a single peak and decay following oral oxybutynin and 2 distinct peaks with intravesical passive diffusion and electromotive oxybutynin. Area under the curve for intravesical passive diffusion were 709 ng. per 8 hours versus oral 1,485 (p <0.05) versus intravesical electromotive 2,781 (p <0.001). Bladder content samples confirmed oxybutynin absorption. Oral oxybutynin caused anticholinergic side effects in 7 of 10 patients. There were no side effects with intravesical passive diffusion or electromotive administrations.

CONCLUSIONS

Accelerated intravesical administration results in greater bioavailability and increased objective benefits without side effects in previously unresponsive patients compared with oral and intravesical passive diffusion oxybutynin administration.