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Steinbüchel M, Menne J, Schröter R, Neugebauer U, Schlatter E, Ciarimboli G. Regulation of Transporters for Organic Cations by High Glucose. Int J Mol Sci 2023; 24:14051. [PMID: 37762353 PMCID: PMC10531077 DOI: 10.3390/ijms241814051] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Revised: 09/08/2023] [Accepted: 09/11/2023] [Indexed: 09/29/2023] Open
Abstract
Endogenous positively charged organic substances, including neurotransmitters and cationic uremic toxins, as well as exogenous organic cations such as the anti-diabetic medication metformin, serve as substrates for organic cation transporters (OCTs) and multidrug and toxin extrusion proteins (MATEs). These proteins facilitate their transport across cell membranes. Vectorial transport through the OCT/MATE axis mediates the hepatic and renal excretion of organic cations, regulating their systemic and local concentrations. Organic cation transporters are part of the remote sensing and signaling system, whose activity can be regulated to cope with changes in the composition of extra- and intracellular fluids. Glucose, as a source of energy, can also function as a crucial signaling molecule, regulating gene expression in various organs and tissues. Its concentration in the blood may fluctuate in specific physiological and pathophysiological conditions. In this work, the regulation of the activity of organic cation transporters was measured by incubating human embryonic kidney cells stably expressing human OCT1 (hOCT1), hOCT2, or hMATE1 with high glucose concentrations (16.7 mM). Incubation with this high glucose concentration for 48 h significantly stimulated the activity of hOCT1, hOCT2, and hMATE1 by increasing their maximal velocity (Vmax), but without significantly changing their affinity for the substrates. These effects were independent of changes in osmolarity, as the addition of equimolar concentrations of mannitol did not alter transporter activity. The stimulation of transporter activity was associated with a significant increase in transporter mRNA expression. Inhibition of the mechanistic target of rapamycin (mTOR) kinase with Torin-1 suppressed the transporter stimulation induced by incubation with 16.7 mM glucose. Focusing on hOCT2, it was shown that incubation with 16.7 mM glucose increased hOCT2 protein expression in the plasma membrane. Interestingly, an apparent trend towards higher hOCT2 mRNA expression was observed in kidneys from diabetic patients, a pathology characterized by high serum glucose levels. Due to the small number of samples from diabetic patients (three), this observation must be interpreted with caution. In conclusion, incubation for 48 h with a high glucose concentration of 16.7 mM stimulated the activity and expression of organic cation transporters compared to those measured in the presence of 5.6 mM glucose. This stimulation by a diabetic environment could increase cellular uptake of the anti-diabetic drug metformin and increase renal tubular secretion of organic cations in an early stage of diabetes.
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Affiliation(s)
| | | | | | | | | | - Giuliano Ciarimboli
- Experimental Nephrology, Department of Internal Medicine D, University Hospital Münster, 48149 Münster, Germany; (M.S.); (J.M.); (R.S.); (U.N.); (E.S.)
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2
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Nies AT, Schaeffeler E, Schwab M. Hepatic solute carrier transporters and drug therapy: Regulation of expression and impact of genetic variation. Pharmacol Ther 2022; 238:108268. [DOI: 10.1016/j.pharmthera.2022.108268] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Revised: 07/25/2022] [Accepted: 08/15/2022] [Indexed: 11/30/2022]
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Markowicz-Piasecka M, Markiewicz A, Darłak P, Sikora J, Adla SK, Bagina S, Huttunen KM. Current Chemical, Biological, and Physiological Views in the Development of Successful Brain-Targeted Pharmaceutics. Neurotherapeutics 2022; 19:942-976. [PMID: 35391662 PMCID: PMC9294128 DOI: 10.1007/s13311-022-01228-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/24/2022] [Indexed: 12/13/2022] Open
Abstract
One of the greatest challenges with successful pharmaceutical treatments of central nervous system (CNS) diseases is the delivery of drugs into their target sites with appropriate concentrations. For example, the physically tight blood-brain barrier (BBB) effectively blocks compounds from penetrating into the brain, also by the action of metabolizing enzymes and efflux transport mechanisms. However, many endogenous compounds, including both smaller compounds and macromolecules, like amino acids, sugars, vitamins, nucleosides, hormones, steroids, and electrolytes, have their peculiar internalization routes across the BBB. These delivery mechanisms, namely carrier-mediated transport and receptor-mediated transcytosis have been utilized to some extent in brain-targeted drug development. The incomplete knowledge of the BBB and the smaller than a desirable number of chemical tools have hindered the development of successful brain-targeted pharmaceutics. This review discusses the recent advancements achieved in the field from the point of medicinal chemistry view and discusses how brain drug delivery can be improved in the future.
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Affiliation(s)
- Magdalena Markowicz-Piasecka
- Laboratory of Bioanalysis, Department of Pharmaceutical Chemistry, Drug Analysis and Radiopharmacy, Medical University of Lodz, ul. Muszyńskiego1, 90-151 Lodz, Poland
| | - Agata Markiewicz
- Students Research Group, Laboratory of Bioanalysis, Department of Pharmaceutical Chemistry, Drug Analysis and Radiopharmacy, Medical University of Lodz, ul. Muszyńskiego 1, 90-151 Lodz, Poland
| | - Patrycja Darłak
- Students Research Group, Laboratory of Bioanalysis, Department of Pharmaceutical Chemistry, Drug Analysis and Radiopharmacy, Medical University of Lodz, ul. Muszyńskiego 1, 90-151 Lodz, Poland
| | - Joanna Sikora
- Department of Bioinorganic Chemistry, Medical University of Lodz, Medical University of Lodz, ul. Muszyńskiego1, 90-151 Lodz, Poland
| | - Santosh Kumar Adla
- School of Pharmacy, Faculty of Health Sciences, University of Eastern Finland, Yliopistonranta 1C, POB 1627, 70211 Kuopio, Finland
- Institute of Organic Chemistry and Biochemistry (IOCB), Czech Academy of Sciences, Flemingovo Namesti 542/2, 160 00 Prague, Czech Republic
| | - Sreelatha Bagina
- Charles River Discovery Research Services Finland Oy, Neulaniementie 4, 70210 Kuopio, Finland
| | - Kristiina M. Huttunen
- School of Pharmacy, Faculty of Health Sciences, University of Eastern Finland, Yliopistonranta 1C, POB 1627, 70211 Kuopio, Finland
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Haberkorn B, Fromm MF, König J. Transport of Drugs and Endogenous Compounds Mediated by Human OCT1: Studies in Single- and Double-Transfected Cell Models. Front Pharmacol 2021; 12:662535. [PMID: 33967805 PMCID: PMC8100673 DOI: 10.3389/fphar.2021.662535] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Accepted: 03/19/2021] [Indexed: 12/11/2022] Open
Abstract
Organic Cation Transporter 1 (OCT1, gene symbol: SLC22A1) is predominately expressed in human liver, localized in the basolateral membrane of hepatocytes and facilitates the uptake of endogenous compounds (e.g. serotonin, acetylcholine, thiamine), and widely prescribed drugs (e.g. metformin, fenoterol, morphine). Furthermore, exogenous compounds such as MPP+, ASP+ and Tetraethylammonium can be used as prototypic substrates to study the OCT1-mediated transport in vitro. Single-transfected cell lines recombinantly overexpressing OCT1 (e.g., HEK-OCT1) were established to study OCT1-mediated uptake and to evaluate transporter-mediated drug-drug interactions in vitro. Furthermore, double-transfected cell models simultaneously overexpressing basolaterally localized OCT1 together with an apically localized export protein have been established. Most of these cell models are based on polarized grown MDCK cells and can be used to analyze transcellular transport, mimicking the transport processes e.g. during the hepatobiliary elimination of drugs. Multidrug and toxin extrusion protein 1 (MATE1, gene symbol: SLC47A1) and the ATP-driven efflux pump P-glycoprotein (P-gp, gene symbol: ABCB1) are both expressed in the canalicular membrane of human hepatocytes and are described as transporters of organic cations. OCT1 and MATE1 have an overlapping substrate spectrum, indicating an important interplay of both transport proteins during the hepatobiliary elimination of drugs. Due to the important role of OCT1 for the transport of endogenous compounds and drugs, in vitro cell systems are important for the determination of the substrate spectrum of OCT1, the understanding of the molecular mechanisms of polarized transport, and the investigation of potential drug-drug interactions. Therefore, the aim of this review article is to summarize the current knowledge on cell systems recombinantly overexpressing human OCT1.
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Affiliation(s)
- Bastian Haberkorn
- Institute of Experimental and Clinical Pharmacology and Toxicology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Martin F Fromm
- Institute of Experimental and Clinical Pharmacology and Toxicology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Jörg König
- Institute of Experimental and Clinical Pharmacology and Toxicology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
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5
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Zhou S, Zeng S, Shu Y. Drug-Drug Interactions at Organic Cation Transporter 1. Front Pharmacol 2021; 12:628705. [PMID: 33679412 PMCID: PMC7925875 DOI: 10.3389/fphar.2021.628705] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Accepted: 01/13/2021] [Indexed: 12/19/2022] Open
Abstract
The interaction between drugs and various transporters is one of the decisive factors that affect the pharmacokinetics and pharmacodynamics of drugs. The organic cation transporter 1 (OCT1) is a member of the Solute Carrier 22A (SLC22A) family that plays a vital role in the membrane transport of organic cations including endogenous substances and xenobiotics. This article mainly discusses the drug-drug interactions (DDIs) mediated by OCT1 and their clinical significance.
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Affiliation(s)
- Shiwei Zhou
- Key Laboratory of Oral Medicine, School and Hospital of Stomatology, Guangzhou Medical University, Guangzhou, China.,Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland at Baltimore, Baltimore, MD, United States.,Department of Thyroid Surgery, The Second Xiangya Hospital, Central South University, Hunan, China
| | - Sujuan Zeng
- Key Laboratory of Oral Medicine, School and Hospital of Stomatology, Guangzhou Medical University, Guangzhou, China
| | - Yan Shu
- Key Laboratory of Oral Medicine, School and Hospital of Stomatology, Guangzhou Medical University, Guangzhou, China.,Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland at Baltimore, Baltimore, MD, United States
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Ciarimboli G. Regulation Mechanisms of Expression and Function of Organic Cation Transporter 1. Front Pharmacol 2021; 11:607613. [PMID: 33732143 PMCID: PMC7959823 DOI: 10.3389/fphar.2020.607613] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Accepted: 12/01/2020] [Indexed: 12/12/2022] Open
Abstract
The organic cation transporter 1 (OCT1) belongs together with OCT2 and OCT3 to the solute carrier family 22 (SLC22). OCTs are involved in the movement of organic cations through the plasma membrane. In humans, OCT1 is mainly expressed in the sinusoidal membrane of hepatocytes, while in rodents, OCT1 is strongly represented also in the basolateral membrane of renal proximal tubule cells. Considering that organic cations of endogenous origin are important neurotransmitters and that those of exogenous origin are important drugs, these transporters have significant physiological and pharmacological implications. Because of the high expression of OCTs in excretory organs, their activity has the potential to significantly impact not only local but also systemic concentration of their substrates. Even though many aspects governing OCT function, interaction with substrates, and pharmacological role have been extensively investigated, less is known about regulation of OCTs. Possible mechanisms of regulation include genetic and epigenetic modifications, rapid regulation processes induced by kinases, regulation caused by protein–protein interaction, and long-term regulation induced by specific metabolic and pathological situations. In this mini-review, the known regulatory processes of OCT1 expression and function obtained from in vitro and in vivo studies are summarized. Further research should be addressed to integrate this knowledge to known aspects of OCT1 physiology and pharmacology.
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Affiliation(s)
- Giuliano Ciarimboli
- Experimental Nephrology, Medicine Clinic D, Münster University Hospital, Münster, Germany
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Substrates and Inhibitors of Organic Cation Transporters (OCTs) and Plasma Membrane Monoamine Transporter (PMAT) and Therapeutic Implications. Handb Exp Pharmacol 2021; 266:119-167. [PMID: 34495395 DOI: 10.1007/164_2021_516] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The gene products of the SLC22A gene family (hOCT1, hOCT2, and hOCT3) and of the SLC29A4 gene (hPMAT or hENT4) are all polyspecific organic cation transporters. Human OCTs (including hPMAT) are expressed in peripheral tissues such as small intestine, liver, and kidney involved in the pharmacokinetics of drugs. In the human brain, all four transporters are expressed at the blood-brain barrier (BBB), hOCT2 is additionally expressed in neurons, and hOCT3 and hPMAT in glia. More than 40% of the presently used drugs are organic cations. This chapter lists and discusses all known drugs acting as substrates or inhibitors of these four organic cation transporters, independently of whether the transporter is expressed in the central nervous system (CNS) or in peripheral tissues. Of interest is their involvement in drug absorption, distribution, and excretion as well as potential OCT-associated drug-drug interactions (DDIs), with a focus on drugs that act in the CNS.
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Gorecki M, Müller SF, Leidolf R, Geyer J. Trospium Chloride Transport by Mouse Drug Carriers of the Slc22 and Slc47 Families. Int J Mol Sci 2020; 22:ijms22010022. [PMID: 33375004 PMCID: PMC7792585 DOI: 10.3390/ijms22010022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Revised: 12/17/2020] [Accepted: 12/18/2020] [Indexed: 12/21/2022] Open
Abstract
Background: The muscarinic receptor antagonist trospium chloride (TCl) is used for pharmacotherapy of the overactive bladder syndrome. TCl is a hydrophilic positively charged drug. Therefore, it has low permeability through biomembranes and requires drug transporters for distribution and excretion. In humans, the organic cation transporters OCT1 and OCT2 and the multidrug and toxin extrusion MATE1 and MATE2-K carriers showed TCl transport. However, their individual role for distribution and excretion of TCl is unclear. Knockout mouse models lacking mOct1/mOct2 or mMate1 might help to clarify their role for the overall pharmacokinetics of TCl. Method: In preparation of such experiments, TCl transport was analyzed in HEK293 cells stably transfected with the mouse carriers mOct1, mOct2, mMate1, and mMate2, respectively. Results: Mouse mOct1, mOct2, and mMate1 showed significant TCl transport with Km values of 58.7, 78.5, and 29.3 µM, respectively. In contrast, mMate2 did not transport TCl but showed MPP+ transport with Km of 60.0 µM that was inhibited by the drugs topotecan, acyclovir, and levofloxacin. Conclusion: TCl transport behavior as well as expression pattern were quite similar for the mouse carriers mOct1, mOct2, and mMate1 compared to their human counterparts.
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Affiliation(s)
| | | | | | - Joachim Geyer
- Correspondence: ; Tel.: +49-641-99-38404; Fax: +49-641-99-38409
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9
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Abstract
The organic cation transporters (OCTs) OCT1, OCT2, OCT3, novel OCT (OCTN)1, OCTN2, multidrug and toxin exclusion (MATE)1, and MATE kidney-specific 2 are polyspecific transporters exhibiting broadly overlapping substrate selectivities. They transport organic cations, zwitterions, and some uncharged compounds and operate as facilitated diffusion systems and/or antiporters. OCTs are critically involved in intestinal absorption, hepatic uptake, and renal excretion of hydrophilic drugs. They modulate the distribution of endogenous compounds such as thiamine, L-carnitine, and neurotransmitters. Sites of expression and functions of OCTs have important impact on energy metabolism, pharmacokinetics, and toxicity of drugs, and on drug-drug interactions. In this work, an overview about the human OCTs is presented. Functional properties of human OCTs, including identified substrates and inhibitors of the individual transporters, are described. Sites of expression are compiled, and data on regulation of OCTs are presented. In addition, genetic variations of OCTs are listed, and data on their impact on transport, drug treatment, and diseases are reported. Moreover, recent data are summarized that indicate complex drug-drug interaction at OCTs, such as allosteric high-affinity inhibition of transport and substrate dependence of inhibitor efficacies. A hypothesis about the molecular mechanism of polyspecific substrate recognition by OCTs is presented that is based on functional studies and mutagenesis experiments in OCT1 and OCT2. This hypothesis provides a framework to imagine how observed complex drug-drug interactions at OCTs arise. Finally, preclinical in vitro tests that are performed by pharmaceutical companies to identify interaction of novel drugs with OCTs are discussed. Optimized experimental procedures are proposed that allow a gapless detection of inhibitory and transported drugs.
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Affiliation(s)
- Hermann Koepsell
- Institute of Anatomy and Cell Biology and Department of Molecular Plant Physiology and Biophysics, Julius-von-Sachs-Institute, University of Würzburg, Würzburg, Germany
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Jensen O, Matthaei J, Blome F, Schwab M, Tzvetkov MV, Brockmöller J. Variability and Heritability of Thiamine Pharmacokinetics With Focus on OCT1 Effects on Membrane Transport and Pharmacokinetics in Humans. Clin Pharmacol Ther 2019; 107:628-638. [PMID: 31593619 DOI: 10.1002/cpt.1666] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2019] [Accepted: 09/08/2019] [Indexed: 12/21/2022]
Abstract
Thiamine is substrate of the hepatic uptake transporter organic cation transporter 1 (OCT1), and pathological lipid metabolism was associated with OCT1-dependent thiamine transport. However, it is unknown whether clinical pharmacokinetics of thiamine is modulated by OCT1 genotype. We analyzed thiamine transport in vitro, thiamine blood concentrations after high-dose and low-dose (nutritional) intake, and heritability of thiamine and thiamine-phosphate blood concentrations. The variant OCT1*2 had reduced and OCT1*3 to OCT1*6 had deficient thiamine uptake activity. However, pharmacokinetics of thiamine did not differ depending on OCT1 genotype. Further studies in primary human hepatocytes indicated that several cation transporters, including OCT1, OCT3, and THTR-2, contribute to hepatic uptake of thiamine. As much as 54% of the variation in thiamine and 75% in variation of thiamine monophosphate plasma concentrations was determined by heritable factors. Apparently, thiamine is not useful as a probe drug for OCT1 activity, but the high heritability, particularly of thiamine monophosphate, may stimulate further genomic research.
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Affiliation(s)
- Ole Jensen
- Department of Clinical Pharmacology, University Medical Center, Georg August University, Goettingen, Germany
| | - Johannes Matthaei
- Department of Clinical Pharmacology, University Medical Center, Georg August University, Goettingen, Germany
| | - Felix Blome
- Department of Clinical Pharmacology, University Medical Center, Georg August University, Goettingen, Germany
| | - Matthias Schwab
- Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology, University of Tübingen, Stuttgart, Germany.,iFIT Cluster of Excellence, University of Tübingen, Tübingen, Germany.,Departments of Clinical Pharmacology, Pharmacy, and Biochemistry, University Tübingen, Tübingen, Germany
| | - Mladen V Tzvetkov
- Department of Clinical Pharmacology, University Medical Center, Georg August University, Goettingen, Germany.,Department of Pharmacology, University Medical Center, Ernst-Moritz-Arndt-University, Greifswald, Germany
| | - Jürgen Brockmöller
- Department of Clinical Pharmacology, University Medical Center, Georg August University, Goettingen, Germany
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Abebe BT, Weiss M, Modess C, Tadken T, Wegner D, Meyer MJ, Schwantes U, Neumeister C, Scheuch E, Schulz HU, Tzvetkov M, Siegmund W. Pharmacokinetic Drug-Drug Interactions Between Trospium Chloride and Ranitidine Substrates of Organic Cation Transporters in Healthy Human Subjects. J Clin Pharmacol 2019; 60:312-323. [PMID: 31542894 DOI: 10.1002/jcph.1523] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Accepted: 08/21/2019] [Indexed: 12/30/2022]
Abstract
Trospium chloride, a muscarinic receptor blocker, is poorly absorbed with different rates from areas in the jejunum and the cecum/ascending colon. To evaluate whether organic cation transporter (OCT) 1, OCT2 and multidrug and toxin extrusion (MATE) 1 and MATE2-K are involved in pharmacokinetics, competitions with ranitidine, a probe inhibitor of the cation transporters, were evaluated in transfected HEK293 cells. Furthermore, a drug interaction study with trospium chloride after intravenous (2 mg) and oral dosing (30 mg) plus ranitidine (300 mg) was performed in 12 healthy subjects and evaluated by noncompartmental analysis and population pharmacokinetic modeling. Ranitidine inhibited OCT1, OCT2, MATE1, and MATE2-K with half maximal inhibitory concentration values of 186 ± 25 µM, 482 ± 105 µM, 134 ± 37 µM, and 35 ± 11 µM, respectively. In contrast to our hypothesis, coadministration of ranitidine did not significantly decrease oral absorption of trospium. Instead, renal clearance was lowered by ∼15% (530 ± 99 vs 460 ± 120 mL/min; P < .05). It is possible that ranitidine was not available in competitive concentrations at the major colonic absorption site, as the inhibitor is absorbed in the small intestine and undergoes degradation by microbiota. The renal effects apparently result from inhibition of MATE1 and/or MATE2-K by ranitidine as predicted by in vitro to in vivo extrapolation. However, all pharmacokinetic changes were not of clinical relevance for the drug with highly variable pharmacokinetics. Intravenous trospium significantly lowered mean absorption time and relative bioavailability of ranitidine, which was most likely caused by muscarinic receptor blocking effects on intestinal motility and water turnover.
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Affiliation(s)
- Bayew Tsega Abebe
- Department of Pharmacology, Center of Drug Absorption and Transport (C_DAT), University Medicine of Greifswald, Greifswald, Germany
| | - Michael Weiss
- Department of Pharmacology, Martin Luther University Halle-Wittenberg, Germany
| | - Christiane Modess
- Department of Pharmacology, Center of Drug Absorption and Transport (C_DAT), University Medicine of Greifswald, Greifswald, Germany
| | - Tobias Tadken
- Department of Pharmacology, Center of Drug Absorption and Transport (C_DAT), University Medicine of Greifswald, Greifswald, Germany
| | - Danilo Wegner
- Department of Pharmacology, Center of Drug Absorption and Transport (C_DAT), University Medicine of Greifswald, Greifswald, Germany
| | - Marleen J Meyer
- Department of Pharmacology, Center of Drug Absorption and Transport (C_DAT), University Medicine of Greifswald, Greifswald, Germany
| | - Ulrich Schwantes
- Department Medical Science/Clinical Research, Dr. Pfleger Arzneimittel GmbH, Bamberg, Germany
| | - Claudia Neumeister
- Department Medical Science/Clinical Research, Dr. Pfleger Arzneimittel GmbH, Bamberg, Germany
| | - Eberhard Scheuch
- Department of Pharmacology, Center of Drug Absorption and Transport (C_DAT), University Medicine of Greifswald, Greifswald, Germany
| | - Hans-Ulrich Schulz
- LAFAA Laboratory for Contract Research in Clinical Pharmacology and Biopharmaceutical Analytics GmbH, Bad Schwartau, Germany
| | - Mladen Tzvetkov
- Department of Pharmacology, Center of Drug Absorption and Transport (C_DAT), University Medicine of Greifswald, Greifswald, Germany
| | - Werner Siegmund
- Department of Pharmacology, Center of Drug Absorption and Transport (C_DAT), University Medicine of Greifswald, Greifswald, Germany
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Leonhäuser D, Kranz J, Leidolf R, Arndt P, Schwantes U, Geyer J, Grosse JO. Expression of components of the urothelial cholinergic system in bladder and cultivated primary urothelial cells of the pig. BMC Urol 2019; 19:62. [PMID: 31288793 PMCID: PMC6617688 DOI: 10.1186/s12894-019-0495-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Accepted: 07/04/2019] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Porcine urinary bladders are widely used for uro-pharmacological examinations due to their resemblance to the human organ. However, characterisations of the porcine urothelium at the molecular level are scarce up to now. As it has become clear over the last years that this tissue plays an important role in the signaling-pathways of the bladder, we examined whether the transporter and receptor pattern (with focus on the transmitter acetylcholine) is comparable to the human urothelium. With regard to in vitro studies, we also investigated if there is a difference between the native tissue and cultivated primary urothelial cells in culture. METHODS Urothelium from German Landrace and Göttingen Minipig bladders was collected. One part of the German Landrace tissue was used for cultivation, and different passages of the urothelial cells were collected. The actual mRNA expression of different transporters and receptors was examined via quantitative real-time PCR. These included the vesicular acetylcholine transporter (VAChT), the choline acetyl transferase (ChAT), organic cation transporters 1-3 (OCT1-3), organic anion transporting polypeptide 1A2 (OATP1A2), P-glycoprotein (ABCB1), the carnitine acetyl-transferase (CarAT), as well as the muscarinic receptors 1-5 (M1-5). RESULTS There is a strong qualitative resemblance between the human and the porcine urothelium with regard to the investigated cholinergic receptors, enzymes and transporters. CarAT, OCT1-3, OATP1A2 and ABCB1 could be detected in the urothelium of both pig races. Moreover, all 5 M-receptors were prominent with an emphasis on M2 and M3. VAChT and ChAT could not be detected at all. Cultures of the derived urothelial cells showed decreased expression of all targets apart from ABCB1 and CarAT. CONCLUSIONS Based on the expression pattern of receptors, transporters and enzymes of the cholinergic system, the porcine urinary bladder can be regarded as a good model for pharmacological studies. However, cultivation of primary urothelial cells resulted in a significant drop in mRNA expression of the targets. Therefore, it can be concluded that the intact porcine urothelium, or the whole pig bladder, may be appropriate models for studies with anticholinergic drugs, whereas cultivated urothelial cells have some limitation due to significant changes in the expression levels of relevant targets.
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Affiliation(s)
- Dorothea Leonhäuser
- Department of Urology, RWTH Aachen University Hospital, Pauwelsstraße 30, 52074, Aachen, Germany
| | - Jasmin Kranz
- Institute of Pharmacology and Toxicology, Biomedical Research Center BFS, Justus Liebig University Giessen, Giessen, Germany
| | - Regina Leidolf
- Institute of Pharmacology and Toxicology, Biomedical Research Center BFS, Justus Liebig University Giessen, Giessen, Germany
| | - Patrick Arndt
- Department of Urology, RWTH Aachen University Hospital, Pauwelsstraße 30, 52074, Aachen, Germany
| | | | - Joachim Geyer
- Institute of Pharmacology and Toxicology, Biomedical Research Center BFS, Justus Liebig University Giessen, Giessen, Germany
| | - Joachim O Grosse
- Department of Urology, RWTH Aachen University Hospital, Pauwelsstraße 30, 52074, Aachen, Germany.
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13
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Deutsch B, Neumeister C, Schwantes U, Fromm MF, König J. Interplay of the Organic Cation Transporters OCT1 and OCT2 with the Apically Localized Export Protein MATE1 for the Polarized Transport of Trospium. Mol Pharm 2019; 16:510-517. [PMID: 30656943 DOI: 10.1021/acs.molpharmaceut.8b00779] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The anticholinergic drug trospium is secreted into urine and, to a smaller extent, into bile. Chemically, it is an organic cation, and it is a substrate of the uptake transporters OCT1 and OCT2 as well as for the export proteins MATE1 and MATE2-K as determined in uptake studies using HEK293 cells. So far, neither MATE-mediated export nor the interplay of OCT-mediated uptake and MATE-mediated export have been investigated. Therefore, we used polarized monolayers of single- and double-transfected MDCKII cells (MDCK-OCT1, MDCK-OCT2, MDCK-MATE1, MDCK-OCT1-MATE1, and MDCK-OCT2-MATE1) and the respective control cells (MDCK-Co) for transcellular transport assays. We demonstrate that the transcellular, basal-to-apical transport of trospium is significantly higher in all cell lines compared to control cells over nearly the complete concentration range tested. The transcellular transport mediated by double-transfected MDCK-OCT1-MATE1 and MDCK-OCT2-MATE1 exceeded that in the single-transfected cells (MDCK-OCT1-MATE1 vs MDCK-OCT1: 2.2-fold; MDCK-OCT1-MATE1 vs MDCK-MATE1: 1.7-fold; MDCK-OCT2-MATE1 vs MDCK-OCT2: 6.1-fold; MDCK-OCT2-MATE1 vs MDCK-MATE1: 1.8-fold at a trospium concentration of 1.0 μM; p < 0.001 each). Thus, we show that MATE1 does not only mediate the uptake of trospium into HEK293 cells but also the efflux of trospium out of polarized MDCKII-cells. Furthermore, our results indicate that OCT1 or OCT2 as uptake transporters and MATE1 as an export protein contribute to the transcellular transport of trospium at concentrations normally reached during trospium therapy. These data suggest that both, OCT-mediated uptake as well as MATE1-mediated efflux may contribute to trospium renal and biliary elimination.
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Affiliation(s)
- Birgit Deutsch
- Institute of Experimental and Clinical Pharmacology and Toxicology , Friedrich-Alexander-Universität Erlangen-Nürnberg , 91054 Erlangen , Germany
| | | | | | - Martin F Fromm
- Institute of Experimental and Clinical Pharmacology and Toxicology , Friedrich-Alexander-Universität Erlangen-Nürnberg , 91054 Erlangen , Germany
| | - Jörg König
- Institute of Experimental and Clinical Pharmacology and Toxicology , Friedrich-Alexander-Universität Erlangen-Nürnberg , 91054 Erlangen , Germany
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14
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Abstract
Transporters in proximal renal tubules contribute to the disposition of numerous drugs. Furthermore, the molecular mechanisms of tubular secretion have been progressively elucidated during the past decades. Organic anions tend to be secreted by the transport proteins OAT1, OAT3 and OATP4C1 on the basolateral side of tubular cells, and multidrug resistance protein (MRP) 2, MRP4, OATP1A2 and breast cancer resistance protein (BCRP) on the apical side. Organic cations are secreted by organic cation transporter (OCT) 2 on the basolateral side, and multidrug and toxic compound extrusion (MATE) proteins MATE1, MATE2/2-K, P-glycoprotein, organic cation and carnitine transporter (OCTN) 1 and OCTN2 on the apical side. Significant drug-drug interactions (DDIs) may affect any of these transporters, altering the clearance and, consequently, the efficacy and/or toxicity of substrate drugs. Interactions at the level of basolateral transporters typically decrease the clearance of the victim drug, causing higher systemic exposure. Interactions at the apical level can also lower drug clearance, but may be associated with higher renal toxicity, due to intracellular accumulation. Whereas the importance of glomerular filtration in drug disposition is largely appreciated among clinicians, DDIs involving renal transporters are less well recognized. This review summarizes current knowledge on the roles, quantitative importance and clinical relevance of these transporters in drug therapy. It proposes an approach based on substrate-inhibitor associations for predicting potential tubular-based DDIs and preventing their adverse consequences. We provide a comprehensive list of known drug interactions with renally-expressed transporters. While many of these interactions have limited clinical consequences, some involving high-risk drugs (e.g. methotrexate) definitely deserve the attention of prescribers.
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Affiliation(s)
- Anton Ivanyuk
- Division of Clinical Pharmacology, Lausanne University Hospital (CHUV), Bugnon 17, 1011, Lausanne, Switzerland.
| | - Françoise Livio
- Division of Clinical Pharmacology, Lausanne University Hospital (CHUV), Bugnon 17, 1011, Lausanne, Switzerland
| | - Jérôme Biollaz
- Division of Clinical Pharmacology, Lausanne University Hospital (CHUV), Bugnon 17, 1011, Lausanne, Switzerland
| | - Thierry Buclin
- Division of Clinical Pharmacology, Lausanne University Hospital (CHUV), Bugnon 17, 1011, Lausanne, Switzerland
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15
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Chen J, Brockmöller J, Seitz T, König J, Chen X, Tzvetkov MV. Tropane alkaloids as substrates and inhibitors of human organic cation transporters of the SLC22 (OCT) and the SLC47 (MATE) families. Biol Chem 2017; 398:237-249. [PMID: 27676604 DOI: 10.1515/hsz-2016-0236] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2016] [Accepted: 09/21/2016] [Indexed: 01/30/2023]
Abstract
Tropane alkaloids and their derivatives are anticholinergic drugs with narrow therapeutic range. Here we characterize the organic cation transporters from the SLC22 (OCT1, OCT2, and OCT3) and the SLC47 families (MATE1 and MATE2-K) as potential mediators of the renal and extra-renal excretion, the two major roads of elimination of these substances. All analyzed compounds inhibited and the quaternary amine derivatives ipratropium and trospium were strongly transported by OCTs and MATEs. Overexpression of OCTs or MATEs in HEK293 cells resulted in an up to 63-fold increase in the uptake of ipratropium (Km of 0.32 μm to OCT2 and Vmax of 3.34 nmol×mg protein-1×min-1 to MATE1). The transcellular transport of ipratropium was 16-fold higher in OCT2-MATE1 and 10-fold higher in OCT1-MATE1 overexpressing compared to control MDCKII cells. Genetic polymorphisms in OCT1 and OCT2 affected ipratropium uptake and clinically relevant concentration of ondansetron and pyrithiamine inhibited ipratropium uptake via MATEs by more than 90%. This study suggests that OCT1, OCT2 and MATEs may be strongly involved in the renal and extra-renal elimination of ipratropium and other quaternary amine alkaloids. These substances have a notoriously narrow therapeutic range and the drug-drug interactions suggested here should be further critically evaluated in humans.
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Stage TB, Lee MP, Hallas J, Christensen MMH, Brøsen K, Christensen K, Gagne JJ, Pottegård A. Early Discontinuation of Metformin in Individuals Treated with Inhibitors of Transporters of Metformin. Basic Clin Pharmacol Toxicol 2016; 118:487-95. [PMID: 27128732 DOI: 10.1111/bcpt.12579] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2015] [Accepted: 03/07/2016] [Indexed: 12/22/2022]
Abstract
The aim of this study was to examine the risk of early discontinuation of metformin as a proxy for intolerance, associated with use of drugs known to inhibit transporters involved in metformin distribution. We analysed all incident users of metformin in Denmark between 2000 and 2012 (n = 132,221) and in a cohort of US patients (n = 296,903). Risk of early discontinuation of metformin was assessed using adjusted logistic regression for 28 drugs putatively inhibiting metformin transporters and four negative controls. Increased odds ratio of early discontinuation of metformin was only associated with codeine, an inhibitor of organic cation transporter 1 in both cohorts [adjusted odds ratio (OR) in Danish cohort (95% CI): 1.13 (1.02-1.26), adjusted OR in American cohort (95% CI): 1.32 (1.19-1.47)]. The remaining drugs were not associated with increased odds ratio of early discontinuation and, surprisingly, four drugs were associated with a decreased risk. These findings indicate that codeine use may be associated with risk of early discontinuation of metformin and could be used as a basis for further investigation.
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Affiliation(s)
- Tore Bjerregaard Stage
- Clinical Pharmacology, Department of Public Health, University of Southern Denmark, Odense, Denmark.,Pharmacometrics Group, Department of Biosciences, Uppsala University, Uppsala, Sweden
| | - Moa P Lee
- Division of Pharmacoepidemiology and Pharmacoeconomics, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
| | - Jesper Hallas
- Clinical Pharmacology, Department of Public Health, University of Southern Denmark, Odense, Denmark
| | | | - Kim Brøsen
- Clinical Pharmacology, Department of Public Health, University of Southern Denmark, Odense, Denmark
| | - Kaare Christensen
- Department of Epidemiology, Biostatistics and Biodemography, Institute of Public Health, University of Southern Denmark, Odense, Denmark
| | - Joshua J Gagne
- Division of Pharmacoepidemiology and Pharmacoeconomics, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
| | - Anton Pottegård
- Clinical Pharmacology, Department of Public Health, University of Southern Denmark, Odense, Denmark
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Stage TB, Brøsen K, Christensen MMH. A Comprehensive Review of Drug-Drug Interactions with Metformin. Clin Pharmacokinet 2016; 54:811-24. [PMID: 25943187 DOI: 10.1007/s40262-015-0270-6] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Metformin is the world's most commonly used oral glucose-lowering drug for type 2 diabetes, and this is mainly because it protects against diabetes-related mortality and all-cause mortality. Although it is an old drug, its mechanism of action has not yet been clarified and its pharmacokinetic pathway is still not fully understood. There is considerable inter-individual variability in the response to metformin, and this has led to many drug-drug interaction (DDI) studies of metformin. In this review, we describe both in vitro and human interaction studies of metformin both as a victim and as a perpetrator. We also clarify the importance of including pharmacodynamic end points in DDI studies of metformin and taking pharmacogenetic variation into account when performing these studies to avoid hidden pitfalls in the interpretation of DDIs with metformin. This evaluation of the literature has revealed holes in our knowledge and given clues as to where future DDI studies should be focused and performed.
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Affiliation(s)
- Tore Bjerregaard Stage
- Clinical Pharmacology, Department of Public Health, University of Southern Denmark, J.B. Winsloews vej 19, 2nd Floor, 5000, Odense, Denmark,
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18
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Role of organic cation transporters (OCTs) in the brain. Pharmacol Ther 2015; 146:94-103. [DOI: 10.1016/j.pharmthera.2014.09.008] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2014] [Accepted: 09/18/2014] [Indexed: 01/04/2023]
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19
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Bexten M, Oswald S, Grube M, Jia J, Graf T, Zimmermann U, Rodewald K, Zolk O, Schwantes U, Siegmund W, Keiser M. 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. Mol Pharm 2014; 12:171-8. [DOI: 10.1021/mp500532x] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
| | | | | | | | | | | | | | - Oliver Zolk
- Institute
of Experimental and Clinical Pharmacology and Toxicology, University of Erlangen-Nuremberg, Erlangen, Germany
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20
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El-Gebali S, Bentz S, Hediger MA, Anderle P. Solute carriers (SLCs) in cancer. Mol Aspects Med 2013; 34:719-34. [PMID: 23506905 DOI: 10.1016/j.mam.2012.12.007] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2012] [Accepted: 12/13/2012] [Indexed: 12/26/2022]
Abstract
During tumor progression cells acquire an altered metabolism, either as a cause or as a consequence of an increased need of energy and nutrients. All four major classes of macromolecules are affected: carbohydrates, proteins, lipids and nucleic acids. As a result of the changed needs, solute carriers (SLCs) which are the major transporters of these molecules are differently expressed. This renders them important targets in the treatment of cancer. Blocking or activating SLCs is one possible therapeutic strategy. For example, some SLCs are upregulated in tumor cells due to the increased demand for energy and nutritional needs. Thus, blocking them and turning off the delivery of fuel or nutrients could be one way to interfere with tumor progression. Specific drug delivery to cancer cells via transporters is another approach. Some SLCs are also interesting as chemosensitizing targets because blocking or activating them may result in an altered response to chemotherapy. In this review we summarize the roles of SLCs in cancer therapy and specifically their potential as direct or indirect targets, as drug carriers or as chemosensitizing targets.
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Affiliation(s)
- Sara El-Gebali
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland
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21
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Oefelein MG, Tong W, Kerr S, Bhasi K, Patel RK, Yu D. Effect of concomitant administration of trospium chloride extended release on the steady-state pharmacokinetics of metformin in healthy adults. Clin Drug Investig 2013; 33:123-31. [PMID: 23325481 PMCID: PMC3561611 DOI: 10.1007/s40261-012-0049-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Background Overactive bladder (OAB) is often associated with a number of co-morbid medical conditions, including diabetes mellitus. This may necessitate several concomitant treatments, thus creating the potential for drug–drug interactions (DDIs). Trospium is renally eliminated, not metabolized via cytochrome P450; therefore, cytochrome P450 DDIs are unlikely. However, coadministration with another renally eliminated drug (e.g., metformin) may theoretically result in a DDI. Objective The objective of this study was to evaluate the pharmacokinetics (plasma and urine) and safety/tolerability of the coadministration of trospium chloride extended release (XR) and metformin under steady-state conditions in healthy male and female subjects. Methods In a single-centre, randomized, open-label, two-group, two-period study in healthy males and females aged 18–45 years, 44 subjects received oral metformin 500 mg twice daily for 3.5 days during one period, and oral trospium chloride XR 60 mg once daily for 10 days, followed by trospium chloride XR 60 mg once daily for 4 days plus metformin 500 mg twice daily for 3.5 days during the other period. The two periods occurred in a crossover fashion, separated by a 3-day washout period. Results Trospium chloride XR coadministration did not alter metformin steady-state pharmacokinetics. Metformin coadministration reduced trospium steady-state maximum plasma concentration (by 34 %) and area under the concentration–time curve from 0–24 hours (by 29 %). Neither drug’s renal clearance was affected. No safety/tolerability issues of concern were observed with coadministration. Conclusion No dosage adjustment is necessary for metformin when coadministered with trospium chloride XR.
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Ciarimboli G. Membrane transporters as mediators of Cisplatin effects and side effects. SCIENTIFICA 2012; 2012:473829. [PMID: 24278698 PMCID: PMC3820462 DOI: 10.6064/2012/473829] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2012] [Accepted: 10/23/2012] [Indexed: 06/02/2023]
Abstract
Transporters are important mediators of specific cellular uptake and thus, not only for effects, but also for side effects, metabolism, and excretion of many drugs such as cisplatin. Cisplatin is a potent cytostatic drug, whose use is limited by its severe acute and chronic nephro-, oto-, and peripheral neurotoxicity. For this reason, other platinum derivatives, such as carboplatin and oxaliplatin, with less toxicity but still with antitumoral action have been developed. Several transporters, which are expressed on the cell membranes, have been associated with cisplatin transport across the plasma membrane and across the cell: the copper transporter 1 (Ctr1), the copper transporter 2 (Ctr2), the P-type copper-transporting ATPases ATP7A and ATP7B, the organic cation transporter 2 (OCT2), and the multidrug extrusion transporter 1 (MATE1). Some of these transporters are also able to accept other platinum derivatives as substrate. Since membrane transporters display a specific tissue distribution, they can be important molecules that mediate the entry of platinum derivatives in target and also nontarget cells possibly mediating specific effects and side effects of the chemotherapeutic drug. This paper summarizes the literature on toxicities of cisplatin compared to that of carboplatin and oxaliplatin and the interaction of these platinum derivatives with membrane transporters.
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Affiliation(s)
- Giuliano Ciarimboli
- Experimentelle Nephrologie, Medizinische Klinik D, Universitätsklinikum Münster, Albert-Schweitzer-Campus 1, Gebäude A14, 48149 Münster, Germany
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Relative bioavailability and pharmacodynamic effects of methantheline compared with atropine in healthy subjects. Eur J Clin Pharmacol 2012; 68:1473-81. [PMID: 22527350 DOI: 10.1007/s00228-012-1286-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2011] [Accepted: 03/27/2012] [Indexed: 10/28/2022]
Abstract
OBJECTIVES Methantheline is a strong muscarinic receptor blocking drug used in the treatment of overactive bladder syndrome, hypersalivation and hyperhidrosis. To provide basic information on the pharmacokinetics, magnitude of pharmacodynamic (PD) effects and their correlations with plasma concentrations, we performed a clinical study in 12 healthy subjects receiving methantheline as immediate-release coated tablets (IR) or in watery solution (SOL) in comparison with atropine and placebo tablets. METHODS The pharmacokinetics and influence of methantheline, atropine and placebo on salivation and accommodation and pupil function (pupillometry: diameter, response to light flash) were studied in a randomized, controlled study after the administration of 100 mg methantheline bromide as IR and in SOL (phase 1) and 1.0 mg atropine sulphate and placebo (phase 2). RESULTS Methantheline reached maximum plasma concentrations of approximately 25 ng/ml after 2.5-3 h and was eliminated at an apparent half-life of approximately 2 h. There was no pharmacokinetic (PK) bioequivalence of methantheline IR and SOL. The ratio IR/SOL (90 % confidence interval) were 0.892 (0.532-1.493) for AUC(0-∞) and 0.905 (0.516-1.584) for maximum plasma concentration. The PD effects of both forms were nearly equivalent with a IR/SOL ratio of 1.015 (0.815-1.262) for salivation, which is the most susceptible characteristic. Methantheline reduced salivation at a potency (methantheline concentration at half maximum effects, EC₅₀) of 5.5 ng/ml in accordance with it plasma concentration. The antimuscarinic effects observed after methantheline administration were stronger and persisted longer than those following the administration of atropine. CONCLUSIONS Methantheline is slowly absorbed but rapidly eliminated in humans, and it exerts a strong effect on salivation which is closely associated with its plasma concentrations following a standard sigmoid PD model. Immediate-release tablets and a watery solution of methantheline are equivalent in terms of major PD effects (salivation, pupil function, heart rate) despite its high PK variability.
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