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Komarova MS, Bukharev AR, Potapieva NN, Tikhonov DB. Modulation of Slow Desensitization ( Tachyphylaxis) of Acid-Sensing Ion Channel (ASIC)1a. Cell Mol Neurobiol 2023; 43:771-783. [PMID: 35201495 DOI: 10.1007/s10571-022-01207-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Accepted: 02/11/2022] [Indexed: 02/03/2023]
Abstract
Among the proton-activated channels of the ASIC family, ASIC1a exhibits a specific tachyphylaxis phenomenon in the form of a progressive decrease in the response amplitude during a series of activations. This process is well known, but its mechanism is poorly understood. Here, we demonstrated a partial reversibility of this effect using long-term whole-cell recording of CHO cells transfected with rASIC1a cDNA. Thus, tachyphylaxis represents a slow desensitization of ASIC1a. Prolonged acidifications provided the same recovery from slow desensitization as short acidifications of the same frequency. Slow desensitization and steady-state desensitization are independent processes although the latter attenuates the development of the former. We found that drugs which facilitate ASIC1a activation (e.g., amitriptyline) cause an enhancement of slow desensitization, while inhibition of ASIC1a by 9-aminoacridine attenuates this process. Overall, for a broad variety of exposures, including increased calcium concentration, different pH conditions, and modulating drugs, we found a correlation between their effects on ASIC1a response amplitude and the development of slow desensitization. Thus, our results demonstrate that slow desensitization occurs only when ASIC1a is in the open state.
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Affiliation(s)
- Margarita S Komarova
- Laboratory of Biophysics of Synaptic Processes, I.M Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg, Russia
| | - Andrey R Bukharev
- Laboratory of Biophysics of Synaptic Processes, I.M Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg, Russia
| | - Natalia N Potapieva
- Laboratory of Biophysics of Synaptic Processes, I.M Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg, Russia
| | - Denis B Tikhonov
- Laboratory of Biophysics of Synaptic Processes, I.M Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg, Russia.
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Boltz A, Radunsky K, Weingessel B, Vécsei-Marlovits VP. Brolucizumab for pre-treated patients with choroidal neovascularization and signs of tachyphylaxis to aflibercept and bevacizumab. Graefes Arch Clin Exp Ophthalmol 2022; 260:2561-2566. [PMID: 35348844 DOI: 10.1007/s00417-022-05634-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Revised: 03/13/2022] [Accepted: 03/19/2022] [Indexed: 01/03/2023] Open
Abstract
PURPOSE Treatment of choroidal neovascularization due to age-related macular degeneration is a challenging topic since an increasing number of patients show reduced morphological response to conventional treatment with intravitreal injections. The present study tested the hypothesis that the newly introduced anti-VEGF antibody brolucizumab does not only show promising results in pre-treated patients but is also a viable option in cases of tachyphylaxis to aflibercept or bevacizumab. METHODS Thirty-six eyes of 34 patients with a history of at least 10 anti-VEGF injections as well as persistent retinal fluid following the past 5 monthly injections with aflibercept and bevacizumab prior to first treatment with brolucizumab were included in the study. Morphological and functional treatment response was compared before and after switching to brolucizumab. RESULTS Mean best-corrected visual acuity did not significantly change after treatment with brolucizumab. In contrast, central retinal thickness significantly decreased 4 weeks after treatment with brolucizumab from 340.36 to 282.22 µm (p < 0.001) as well as pigment epithelial detachment from 346.73 to 280.47 µm (p < 0.001). In 24 eyes (66.67%), complete resolution of intra-and subretinal fluid was observed after a single dose of brolucizumab. No serious adverse events, such as intraocular inflammation and retinal vasculitis, were reported after a single injection of brolucizumab. CONCLUSION Brolucizumab is not only effective in treatment-naïve patients as shown in the pivotal HAWK and Harrier trials, but also in pre-treated patients as seen in the present study. Our data also suggest that brolucizumab is potent in patients with signs of tachyphylaxis to other anti-VEGF agents and thus a viable treatment option.
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Affiliation(s)
- Agnes Boltz
- Department of Ophthalmology, Hietzing Hospital, Wolkersbergenstraße 1, 1130, Vienna, Austria.
- Karl-Landsteiner Institute for Process Optimization and Quality Management in Cataract Surgery, Vienna, Austria.
| | - Katharina Radunsky
- Department of Ophthalmology, Hietzing Hospital, Wolkersbergenstraße 1, 1130, Vienna, Austria
- Karl-Landsteiner Institute for Process Optimization and Quality Management in Cataract Surgery, Vienna, Austria
| | - Birgit Weingessel
- Department of Ophthalmology, Hietzing Hospital, Wolkersbergenstraße 1, 1130, Vienna, Austria
- Karl-Landsteiner Institute for Process Optimization and Quality Management in Cataract Surgery, Vienna, Austria
| | - Veronika Pia Vécsei-Marlovits
- Department of Ophthalmology, Hietzing Hospital, Wolkersbergenstraße 1, 1130, Vienna, Austria
- Karl-Landsteiner Institute for Process Optimization and Quality Management in Cataract Surgery, Vienna, Austria
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3
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Skaff R. Tachyphylaxis and desensitization depression. CNS Spectr 2021; 26:191-2. [PMID: 31656208 DOI: 10.1017/S1092852919001445] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Chapman RW, Li Z, Chun D, Gauani H, Malinin V, Plaunt AJ, Cipolla D, Perkins WR, Corboz MR. Treprostinil palmitil, an inhaled long-acting pulmonary vasodilator, does not show tachyphylaxis with daily dosing in rats. Pulm Pharmacol Ther 2021; 66:101983. [PMID: 33346142 DOI: 10.1016/j.pupt.2020.101983] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Revised: 11/06/2020] [Accepted: 12/09/2020] [Indexed: 01/22/2023]
Abstract
BACKGROUND Treprostinil palmitil (TP) is an inhaled long-acting pulmonary vasodilator prodrug of treprostinil (TRE) that has been formulated for delivery as a suspension (treprostinil palmitil inhalation suspension; TPIS) and as a dry powder (treprostinil palmitil inhalation powder; TPIP). In humans, tachyphylaxis is frequently observed with continuous intravenous (IV) or subcutaneous (SC) infusion of TRE and requires dosage escalation to maintain activity. The aim of the present study was to determine whether tachyphylaxis occurs with repeat daily administration of inhaled TPIS. METHODS Experiments were performed in male Sprague-Dawley rats prepared with a telemetry probe implanted into the right ventricle to measure the change in right ventricular pulse pressure (ΔRVPP) induced by exposure to a 10% oxygen gas mixture. TPIS (6 mL) at concentrations of 0.25, 0.5, and 1 mM was given by nose-only inhalation using an Aeroneb Pro nebulizer, either as a single administration or daily for 16 or 32 consecutive days. In studies involving consecutive daily administrations of TPIS, the delivered TP dosage was 140.3 μg/kg at 1 mM and ranged from 40.2 to 72.2 μg/kg at 0.5 mM. A separate cohort of telemetered rats received continuous IV infusion of TRE via an Alzet mini-pump at a dosage rate of 250 ng/kg/min for 16 days. Blood and lung tissue samples were obtained, and the concentration of TRE in the plasma and TRE and TP in the lungs were measured approximately 1 h after TPIS administration. RESULTS Dose-response studies with TPIS administered as a single administration inhibited the hypoxia-induced increase in RVPP in both a concentration-dependent (0.25, 0.5, and 1 mM) and time-dependent (1-24 h) manner. TPIS, given QD or BID at inhaled doses ranging from 40.2 to 140.3 μg/kg for 16 or 32 consecutive days, produced statistically significant (P < .05) inhibition of the increase of RVPP due to hypoxia over the full duration of the dosing periods. By contrast, the inhibition of the hypoxia-induced increase in RVPP observed with IV TRE infusion (250 ng/kg/min) disappeared after 16 days of infusion. The plasma concentrations of TRE were significantly higher after IV TRE (range, 2.85-13.35 ng/mL) compared to inhaled TPIS (range, 0.22-0.73 ng/mL) CONCLUSIONS: There was no evidence of tachyphylaxis with repeat daily dosing of TPIS for a period of up to 32 days. The absence of tachyphylaxis with TPIS is likely related to its local vasodilatory effects within the lungs, combined with an absence of sustained high plasma concentrations of TRE.
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Kious BM, Bakian AV. Evidence of new-onset depression among persons with migraine after discontinuing antidepressants. Psychiatry Res 2020; 288:112990. [PMID: 32353695 DOI: 10.1016/j.psychres.2020.112990] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Revised: 04/05/2020] [Accepted: 04/06/2020] [Indexed: 10/24/2022]
Abstract
Antidepressants have been hypothesized to cause tardive dysphoria-the delayed development of negative emotional symptoms. We assessed the risk of tardive dysphoria in a cohort of persons with migraine taking anti-migraine antidepressants with no known diagnosis of any mood or anxiety disorder. We included all outpatient encounters in a university hospital system for migraine from January 2008 through October 2018, excluding subjects with prior psychiatric diagnoses. Kaplan-Meier survival curves and multivariable Cox proportional hazards analyses were conducted. 13,048 subjects were included; 1191 took an antidepressant; 402 discontinued an antidepressant. In multivariable analyses examining the first year after exposure, antidepressant use was not significantly associated with risk of a depression, any mood disorder (including depression, mania, and other mood disorders), or anxiety. Antidepressant discontinuation was significantly associated with increased risk of depression, but not any mood disorder or anxiety. Among persons with migraine with no known psychiatric diagnosis, antidepressants did not appear to be associated with indicators of tardive dysphoria. Antidepressant discontinuation, however, was associated with increased risk of a depression diagnosis.
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Affiliation(s)
- Brent M Kious
- Department of Psychiatry, University of Utah, Salt Lake City, Utah, United States.
| | - Amanda V Bakian
- Department of Psychiatry, University of Utah, Salt Lake City, Utah, United States
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Nauck MA, Holle H, Kahle M, Tytko A, Deacon CF, Holst JJ, Meier JJ. No evidence of tachyphylaxis for insulinotropic actions of glucose-dependent insulinotropic polypeptide (GIP) in subjects with type 2 diabetes, their first-degree relatives, or in healthy subjects. Peptides 2020; 125:170176. [PMID: 31669136 DOI: 10.1016/j.peptides.2019.170176] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Revised: 10/12/2019] [Accepted: 10/14/2019] [Indexed: 01/10/2023]
Abstract
BACKGROUND, AIMS In patients with type 2 diabetes, the lost insulinotropic effect of the incretin hormone glucose-dependent insulinotropic polypeptide (GIP) is more apparent after continuous versus bolus administration. To test whether the difference might be explained by rapid tachyphylaxis in response to elevated concentrations of GIP, and whether patients with type 2 diabetes and their relatives are more susceptible to tachyphylaxis than healthy subjects. PATIENTS AND METHODS In a two-way crossover design, insulinotropic responses to repeated bolus injection (50 pmol/kg body weight at 30 and 120 min) and continuous infusion of GIP (2 pmol.kg-1.min-1 from 30 to 180 min) under hyperglycaemic clamp conditions (8.5 mmol/l) was compared in age- gender- and weight-matched patients with type 2 diabetes, first degree relatives of such patients, and healthy subjects. RESULTS Insulin secretory responses to the first and second GIP bolus were not significantly different in any of the subject groups. Subjects with type 2 diabetes had a significant relative impairment versus healthy subjects with continuous (C-peptide, -13.2 %, p < 0.05), but not with repeated bolus administration of GIP (+11.1 %, n.s.). First-degree relatives tended to hyper-secrete insulin with bolus or continuous administrations of GIP. CONCLUSIONS Rapid tachyphylaxis in response to continuous exposure to slightly supraphysiological concentrations of GIP does not explain the reduced insulinotropic response to GIP infusions in patients with type 2 diabetes or their first-degree relatives.
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Affiliation(s)
- M A Nauck
- Diabeteszentrum Bad Lauterberg, Bad Lauterberg im Harz, Germany; Diabetes Center Bochum-Hattingen, St. Josef-Hospital, Ruhr-University Bochum, Bochum, Germany.
| | - H Holle
- Diabeteszentrum Bad Lauterberg, Bad Lauterberg im Harz, Germany
| | - M Kahle
- Diabeteszentrum Bad Lauterberg, Bad Lauterberg im Harz, Germany; Diabetes Center Bochum-Hattingen, St. Josef-Hospital, Ruhr-University Bochum, Bochum, Germany
| | - A Tytko
- Diabeteszentrum Bad Lauterberg, Bad Lauterberg im Harz, Germany
| | - C F Deacon
- Novo Nordisk Foundation Center for Basic Metabolic Research and Department of Biomedical Sciences, Panum Institute, University of Copenhagen, Copenhagen, Denmark
| | - J J Holst
- Novo Nordisk Foundation Center for Basic Metabolic Research and Department of Biomedical Sciences, Panum Institute, University of Copenhagen, Copenhagen, Denmark
| | - J J Meier
- Diabetes Center Bochum-Hattingen, St. Josef-Hospital, Ruhr-University Bochum, Bochum, Germany
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Michaelis KA, Norgard MA, Levasseur PR, Olson B, Burfeind KG, Buenafe AC, Zhu X, Jeng S, McWeeney SK, Marks DL. Persistent Toll-like receptor 7 stimulation induces behavioral and molecular innate immune tolerance. Brain Behav Immun 2019; 82:338-53. [PMID: 31499172 DOI: 10.1016/j.bbi.2019.09.004] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/17/2019] [Revised: 09/04/2019] [Accepted: 09/05/2019] [Indexed: 12/18/2022] Open
Abstract
Toll-like receptors 7 and 8 (TLR7 and TLR8) are endosomal pattern recognition receptors that detect a variety of single-stranded RNA species. While TLR7/8 agonists have robust therapeutic potential, clinical utility of these agents is limited by sickness responses associated with treatment induction. To understand the kinetics and mechanism of these responses, we characterized the acute and chronic effects of TLR7 stimulation. Single-cell RNA-sequencing studies, RNAscope, and radiolabeled in situ hybridization demonstrate that central nervous system gene expression of TLR7 is exclusive to microglia. In vitro studies demonstrate that microglia are highly sensitive to TLR7 stimulation, and respond in a dose-dependent manner to the imidazoquinoline R848. In vivo, both intraperitoneal (IP) and intracerebroventricular (ICV) R848 induce acute sickness responses including hypophagia, weight loss, and decreased voluntary locomotor activity, associated with increased CNS pro-inflammatory gene expression and changes to glial morphology. However, chronic daily IP R848 resulted in rapid tachyphylaxis of behavioral and molecular manifestations of illness. In microglial in vitro assays, pro-inflammatory transcriptional responses rapidly diminished in the context of repeated R848. In addition to TLR7 desensitization, we found that microglia become partially refractory to lipopolysaccharide (LPS) following R848 pretreatment, associated with induction of negative regulators A20 and Irak3. Similarly, mice pre-treated with R848 demonstrate reduced sickness responses, hypothalamic inflammation, and hepatic inflammation in response to LPS. These data combined demonstrate that TLR7 stimulation induces acute behavioral and molecular evidence of sickness responses. Following prolonged dosing, R848 induces a refractory state to both TLR7 and TLR4 activation, consistent with induced immune tolerance.
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Hara C, Wakabayashi T, Fukushima Y, Sayanagi K, Kawasaki R, Sato S, Sakaguchi H, Nishida K. Tachyphylaxis during treatment of exudative age-related macular degeneration with aflibercept. Graefes Arch Clin Exp Ophthalmol 2019; 257:2559-69. [PMID: 31482277 DOI: 10.1007/s00417-019-04456-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Revised: 08/18/2019] [Accepted: 08/27/2019] [Indexed: 10/26/2022] Open
Abstract
PURPOSE At present, the standard treatment of neovascular age-related macular degeneration (AMD) is the repeated administration of antivascular endothelial growth factor (VEGF) agents. However, we often encounter patients who develop tachyphylaxis for anti-VEGF agents. In this study, we investigated the characteristics of patients who developed tachyphylaxis on repeated intravitreal aflibercept (IVA) injections for neovascular AMD and the frequency of tachyphylaxis. METHODS Three hundred thirteen eyes (313 patients) with treatment-naïve AMD who achieved resolution soon after starting IVA and were followed up for ≥ 12 months were enrolled in this retrospective, interventional, consecutive case series. The eyes were investigated for tachyphylaxis to aflibercept. Tachyphylaxis was defined as absence of any improvement (more than 100 μm) in or worsening of CRT within 1 month after more than two repeated monthly IVA injections when the exudative change remained. RESULTS Twenty-eight (8.9%) of the 313 eyes developed tachyphylaxis (occult with no classic, n = 14; polypoidal choroidal vasculopathy, n = 14) at an annual rate of about 3%. The mean number of IVA injections was 10.5 ± 7.8, and the mean interval until tachyphylaxis was 20.9 ± 14.0 months. There was a significant difference in the AMD subtypes between the group with tachyphylaxis and the group without it (p = 0.0029). Occult with no classic type and polypoidal choroidal vasculopathy were the only AMD subtypes in the eyes with tachyphylaxis. In the analysis of the eyes that had occult with no classic or polypoidal choroidal vasculopathy, only intraretinal edema was significantly less common (p = 0.042). A combination of photodynamic therapy and aflibercept was effective in 13 (87%) of 15 eyes with tachyphylaxis, and switching to intravitreal ranibizumab was effective in 5 (56%) of 9 eyes. CONCLUSIONS Tachyphylaxis occurs after repeated IVA injections in a minority of patients with AMD for a long term and is more likely to occur in eyes with lesions beneath the retinal pigment epithelium and no intraretinal edema. Treatment of AMD should be performed keeping this fact in mind, while considering the consecutive treatment.
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Bavli Y, Winkler I, Chen BM, Roffler S, Cohen R, Szebeni J, Barenholz Y. Doxebo (doxorubicin-free Doxil-like liposomes) is safe to use as a pre-treatment to prevent infusion reactions to PEGylated nanodrugs. J Control Release 2019; 306:138-148. [PMID: 31176656 DOI: 10.1016/j.jconrel.2019.06.007] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Revised: 05/30/2019] [Accepted: 06/05/2019] [Indexed: 12/17/2022]
Abstract
The increasing use in the last decade of PEGylated nanodrugs such as Doxil® has seen a rise in the number of associated occurrences of hypersensitivity reactions (HSRs). These reactions (also called infusion reactions or IR), can range from harmless symptoms to life-threatening reactions. Current means to prevent IR include the prophylactic use of antihistamines and steroids, but they cannot ensure total prevention. We previously showed that an intravenous injection of doxorubicin-free Doxil-like PEGylated nano-liposomes (Doxebo) prior to Doxil treatment suppresses Doxil-induced complement activation-related pseudoallergy (CARPA) in pigs, a model of human hypersensitivity reactions to Doxil. However, in order to use Doxebo to prevent Doxil-induced IR, we have to prove its safety and that it does not affect Doxil's performance. Here we show that Doxebo itself does not have toxic effects on the host or tumor, and it does not interfere with Doxil's antitumor activity in mice. Blood, microscopic and macroscopic organ evaluation of rats after repeated administration confirm the lack of intrinsic adverse effect of Doxebo. Likewise, the repeated injection of Doxebo before Doxil did not impact Doxil's pharmacokinetics in plasma and therefore does not cause accelerated blood clearance (ABC). Taken together with our previous publications, these data suggest that the injection of Doxebo prior to Doxil administration can help protect against Doxil-induced IR without adversely affecting treatment efficacy and safety.
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Affiliation(s)
- Yaelle Bavli
- Laboratory of Membrane and Liposome Research, IMRIC, Hebrew University - Hadassah Medical School, Jerusalem, Israel
| | | | - Bing Mae Chen
- Institute of Biomedical Sciences, Academia Sinica, Taipei 11529, Taiwan
| | - Steve Roffler
- Institute of Biomedical Sciences, Academia Sinica, Taipei 11529, Taiwan
| | - Rivka Cohen
- Laboratory of Membrane and Liposome Research, IMRIC, Hebrew University - Hadassah Medical School, Jerusalem, Israel
| | - Janos Szebeni
- Nanomedicine Research and Education Center, Department of Pathophysiology, Semmelweis University, Budapest, Hungary; SeroScience Ltd, Cambridge, MA, United States
| | - Yechezkel Barenholz
- Laboratory of Membrane and Liposome Research, IMRIC, Hebrew University - Hadassah Medical School, Jerusalem, Israel.
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Kinrys G, Gold AK, Pisano VD, Freeman MP, Papakostas GI, Mischoulon D, Nierenberg AA, Fava M. Tachyphylaxis in major depressive disorder: A review of the current state of research. J Affect Disord 2019; 245:488-497. [PMID: 30439676 DOI: 10.1016/j.jad.2018.10.357] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/05/2018] [Revised: 10/08/2018] [Accepted: 10/27/2018] [Indexed: 12/27/2022]
Abstract
BACKGROUND Patients with major depressive disorder (MDD) often experience a re-emergence or worsening of symptoms despite ongoing treatment with previously effective antidepressant pharmacotherapy. This lost or reduced antidepressant response during maintenance, referred to as tachyphylaxis, negatively impacts treatment outcomes and quality of life for patients with MDD. This review assesses the prevalence of antidepressant tachyphylaxis as well as the evidence for interventions to manage it. METHODS We searched PubMed/Medline for the relevant clinical trials and meta-analyses on antidepressant tachyphylaxis up to January 2017. Search terms included "depression" paired with "treatment" (n = 186,674), "tachyphylaxis" paired with "depression" (n = 112), "tachyphylaxis" paired with "major depressive disorder" (n = 21), and "antidepressant" paired with "tachyphylaxis" (n = 68). Studies were included if they reported on a clinical trial or meta-analysis exploring tachyphylaxis in MDD and were excluded if the sample population did not have a primary DSM diagnosis of MDD. RESULTS Rates of tachyphylaxis varied from 9% to 57% depending on the patient population and duration of follow-up. Limited evidence suggests potentially beneficial strategies for managing tachyphylaxis, including change in antidepressant dosing, switch of class of antidepressant medication, augmentation or combination pharmacotherapy, and psychotherapy. LIMITATIONS Studies of antidepressant tachyphylaxis are largely heterogeneous in nature and employ strict inclusion/exclusion criteria; thus, these findings may not be generalizable to all depressed populations. CONCLUSION Few established treatment strategies exist to manage antidepressant tachyphylaxis. Further interventional research is needed to provide symptomatic relief for patients with tachyphylaxis in MDD.
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Affiliation(s)
- Gustavo Kinrys
- Clinical Trials Network and Institute, Massachusetts General Hospital, Boston, MA, USA; Harvard Medical School, Boston, MA, USA.
| | - Alexandra K Gold
- Department of Psychological & Brain Sciences, Boston University, Boston, MA, USA
| | - Vincent D Pisano
- Clinical Trials Network and Institute, Massachusetts General Hospital, Boston, MA, USA
| | - Marlene P Freeman
- Clinical Trials Network and Institute, Massachusetts General Hospital, Boston, MA, USA; Harvard Medical School, Boston, MA, USA
| | - George I Papakostas
- Clinical Trials Network and Institute, Massachusetts General Hospital, Boston, MA, USA; Harvard Medical School, Boston, MA, USA
| | - David Mischoulon
- Clinical Trials Network and Institute, Massachusetts General Hospital, Boston, MA, USA; Harvard Medical School, Boston, MA, USA
| | - Andrew A Nierenberg
- Clinical Trials Network and Institute, Massachusetts General Hospital, Boston, MA, USA; Department of Psychiatry, Massachusetts General Hospital, Boston, MA, USA
| | - Maurizio Fava
- Clinical Trials Network and Institute, Massachusetts General Hospital, Boston, MA, USA; Harvard Medical School, Boston, MA, USA
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Dohar JE. Sialorrhea & aspiration control - A minimally invasive strategy uncomplicated by anticholinergic drug tolerance or tachyphylaxis. Int J Pediatr Otorhinolaryngol 2019; 116:97-101. [PMID: 30554718 DOI: 10.1016/j.ijporl.2018.10.035] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Revised: 10/20/2018] [Accepted: 10/22/2018] [Indexed: 11/21/2022]
Abstract
OBJECTIVE Sialorrhea complicated by aspiration is a primary source of morbidity and mortality in neurologically impaired children. Anticholinergics are an effective treatment option, but have traditionally been considered only adjuncts due to tachyphylaxis and drug tolerance. Similarly, Botox-A® salivary gland injections are also considered adjunctive due to the need to repeat treatment every 3 months. This retrospective case series assessed these two adjunctive strategies used in combination as definitive minimally invasive primary treatment. METHODS 112 subjects diagnosed with sialorrhea and treated at UPMC Children's Hospital of Pittsburgh between 2004 and 2011 were identified. Charts were carefully reviewed for pertinent information regarding the treatment of their sialorrhea and related outcomes. RESULTS Over half of the subject undergoing BTX-A injections were able to reduce their dosage of anticholinergics after receiving injection (58%, n = 28 for glycopyrrolate users and 61%, n = 20 for scopolamine users). Subjects experienced a significant reduction in days spent in the hospital in the year following Botox-A® injection (P-Value = 0.03), and the number of pneumonia episodes in the year following injection (P-Value = 0.04). CONCLUSION Patients treated effectively with both BTX-A injections into their salivary glands and anticholinergics developed neither tachyphylaxis nor drug tolerance with up to 9.6 years of continuous treatment. During the year following combined therapy, patients' average length hospital stay was reduced by a full week and the number of pneumonia episodes was statistically decreased. The failure rate of combined therapy was below that reported for any other intervention or combination of interventions in the literature. Finally, patients did not require BTX-A re-injection at the reported frequency. We hypothesize that anticholinergic medications competitively block acetylcholine attachment to post-synaptic receptors while BTX-A inhibits acetylcholine release at the pre-synaptic terminal, tachyphylaxis/drug tolerance mechanisms resulting in up-regulation of post-synaptic receptors are disrupted. Although salivary production may increase in the year following BTX-A injection, there is enough remaining activity at a molecular level to inhibit release of acetylcholine allowing salvage with anticholinergic medications at tolerable dosages.
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Bosman RC, Waumans RC, Jacobs GE, Oude Voshaar RC, Muntingh AD, Batelaan NM, van Balkom AJ. Failure to Respond after Reinstatement of Antidepressant Medication: A Systematic Review. Psychother Psychosom 2018; 87:268-275. [PMID: 30041180 PMCID: PMC6191880 DOI: 10.1159/000491550] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Accepted: 06/23/2018] [Indexed: 12/27/2022]
Abstract
BACKGROUND Following remission of an anxiety disorder or a depressive disorder, antidepressants are frequently discontinued and in the case of symptom occurrence reinstated. Reinstatement of antidepressants seems less effective in some patients, but an overview is lacking. This systematic review aimed to provide insight into the magnitude and risk factors of response failure after reinstatement of antidepressants in patients with anxiety disorders, depressive disorders, obsessive-compulsive disorder (OCD), or posttraumatic stress disorder (PTSD). METHOD PubMed, Embase, and trial registers were systematically searched for studies in which patients: (1) had an anxiety disorder, a depressive disorder, OCD, or PTSD and (2) experienced failure to respond after reinstatement of a previously effective antidepressant. RESULTS Ten studies reported failure to respond following antidepressant reinstatement. The phenomenon was observed in 16.5% of patients with a depressive disorder, OCD, and social phobia and occurred in all common classes of antidepressants. The range of response failure was broad, varying between 3.8 and 42.9% across studies. No risk factors for failure to respond were investigated. The overall study quality was limited. CONCLUSION Research investigating response failure is scarce and the study quality limited. Response failure occurred in a substantial minority of patients. Contributors to the relevance of this phenomenon are the prevalence of the investigated disorders, the number of patients being treated with antidepressants, and the occurrence of response failure for all common classes of antidepressants. This systematic review highlights the need for studies systematically investigating this phenomenon and associated risk factors.
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Affiliation(s)
- Renske C. Bosman
- Department of Psychiatry, Amsterdam Public Health research institute, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands,GGZ inGeest, Amsterdam, the Netherlands,*Renske C. Bosman, Department of Psychiatry, VU University Medical Center Amsterdam, Oldenaller 1, NL–1081 HL Amsterdam (The Netherlands), E-Mail
| | - Ruth C. Waumans
- Department of Psychiatry, Amsterdam Public Health research institute, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands,GGZ inGeest, Amsterdam, the Netherlands
| | - Gabriel E. Jacobs
- Department of Psychiatry, Leiden University Medical Centre, Leiden, the Netherlands,Centre for Human Drug Research, Leiden, the Netherlands
| | - Richard C. Oude Voshaar
- University of Groningen, University Medical Center Groningen, Department of Psychiatry, Groningen, the Netherlands
| | - Anna D.T. Muntingh
- Department of Psychiatry, Amsterdam Public Health research institute, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands,GGZ inGeest, Amsterdam, the Netherlands
| | - Neeltje M. Batelaan
- Department of Psychiatry, Amsterdam Public Health research institute, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands,GGZ inGeest, Amsterdam, the Netherlands
| | - Anton J.L.M. van Balkom
- Department of Psychiatry, Amsterdam Public Health research institute, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands,GGZ inGeest, Amsterdam, the Netherlands
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Bosman RC, Waumans RC, Jacobs GE, Oude Voshaar RC, Muntingh ADT, Batelaan NM, van Balkom AJLM. Failure to Respond after Reinstatement of Antidepressant Medication: A Systematic Review. Psychother Psychosom 2018. [PMID: 30041180 DOI: 10.1159/000491550)] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
BACKGROUND Following remission of an anxiety disorder or a depressive disorder, antidepressants are frequently discontinued and in the case of symptom occurrence reinstated. Reinstatement of antidepressants seems less effective in some patients, but an overview is lacking. This systematic review aimed to provide insight into the magnitude and risk factors of response failure after reinstatement of antidepressants in patients with anxiety disorders, depressive disorders, obsessive-compulsive disorder (OCD), or posttraumatic stress disorder (PTSD). METHOD PubMed, Embase, and trial registers were systematically searched for studies in which patients: (1) had an anxiety disorder, a depressive disorder, OCD, or PTSD and (2) experienced failure to respond after reinstatement of a previously effective antidepressant. RESULTS Ten studies reported failure to respond following antidepressant reinstatement. The phenomenon was observed in 16.5% of patients with a depressive disorder, OCD, and social phobia and occurred in all common classes of antidepressants. The range of response failure was broad, varying between 3.8 and 42.9% across studies. No risk factors for failure to respond were investigated. The overall study quality was limited. CONCLUSION Research investigating response failure is scarce and the study quality limited. Response failure occurred in a substantial minority of patients. Contributors to the relevance of this phenomenon are the prevalence of the investigated disorders, the number of patients being treated with antidepressants, and the occurrence of response failure for all common classes of antidepressants. This systematic review highlights the need for studies systematically investigating this phenomenon and associated risk factors.
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Affiliation(s)
- Renske C Bosman
- Department of Psychiatry, Amsterdam Public Health research institute, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands.,GGZ inGeest, Amsterdam, the Netherlands
| | - Ruth C Waumans
- Department of Psychiatry, Amsterdam Public Health research institute, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands.,GGZ inGeest, Amsterdam, the Netherlands
| | - Gabriel E Jacobs
- Department of Psychiatry, Leiden University Medical Centre, Leiden, the Netherlands.,Centre for Human Drug Research, Leiden, the Netherlands
| | - Richard C Oude Voshaar
- University of Groningen, University Medical Center Groningen, Department of Psychiatry, Groningen, the Netherlands
| | - Anna D T Muntingh
- Department of Psychiatry, Amsterdam Public Health research institute, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands.,GGZ inGeest, Amsterdam, the Netherlands
| | - Neeltje M Batelaan
- Department of Psychiatry, Amsterdam Public Health research institute, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands.,GGZ inGeest, Amsterdam, the Netherlands
| | - Anton J L M van Balkom
- Department of Psychiatry, Amsterdam Public Health research institute, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands.,GGZ inGeest, Amsterdam, the Netherlands
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Jiang YM, Huang C, Peng Z, Han SL, Li WG, Zhu MX, Xu TL. Acidosis counteracts itch tachyphylaxis to consecutive pruritogen exposure dependent on acid-sensing ion channel 3. Mol Pain 2018; 13:1744806917721114. [PMID: 28745101 PMCID: PMC5533257 DOI: 10.1177/1744806917721114] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Tachyphylaxis of itch refers to a markedly reduced scratching response to consecutive exposures of a pruritogen, a process thought to protect against tissue damage by incessant scratching and to become disrupted in chronic itch. Here, we report that a strong stimulation of the Mas-related G-protein-coupled receptor C11 by its agonist, Ser-Leu-Ile-Gly-Arg-Leu-NH2 (SL-NH2) or bovine adrenal medulla 8-22 peptide, via subcutaneous injection in mice induces tachyphylaxis to the subsequent application of SL-NH2 to the same site. Notably, co-application of acid and SL-NH2 following the initial injection of the pruritogen alone counteracted itch tachyphylaxis by augmenting the scratching behaviors in wild-type but not in acid-sensing ion channel 3-null, animals. Using an activity-dependent silencing strategy, we identified that acid-sensing ion channel 3-mediated itch enhancement mainly occurred via the Mas-related G-protein-coupled receptor C11-responsive sensory neurons. Together, our results indicate that acid-sensing ion channel 3, activated by concomitant acid and certain pruritogens, constitute a novel signaling pathway that counteracts itch tachyphylaxis to successive pruritogenic stimulation, which likely contributes to chronic itch associated with tissue acidosis.
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Affiliation(s)
- Yi-Ming Jiang
- 1 Department of Anatomy and Physiology, Collaborative Innovation Center for Brain Science, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Chen Huang
- 1 Department of Anatomy and Physiology, Collaborative Innovation Center for Brain Science, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Zhong Peng
- 1 Department of Anatomy and Physiology, Collaborative Innovation Center for Brain Science, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Shao-Ling Han
- 1 Department of Anatomy and Physiology, Collaborative Innovation Center for Brain Science, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Wei-Guang Li
- 1 Department of Anatomy and Physiology, Collaborative Innovation Center for Brain Science, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Michael Xi Zhu
- 2 Department of Integrative Biology and Pharmacology, University of Texas Health Science Center, Houston, TX, USA
| | - Tian-Le Xu
- 1 Department of Anatomy and Physiology, Collaborative Innovation Center for Brain Science, Shanghai Jiao Tong University School of Medicine, Shanghai, China
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Turkalj M, Živković J, Lipej M, Bulat Lokas S, Erceg D, Anzić SA, Magdić R, Plavec D. The effect of mouth breathing on exercise induced fall in lung function in children with allergic asthma and rhinitis. Int J Pediatr Otorhinolaryngol 2016; 86:53-6. [PMID: 27260579 DOI: 10.1016/j.ijporl.2016.04.020] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/24/2015] [Revised: 04/13/2016] [Accepted: 04/14/2016] [Indexed: 11/29/2022]
Abstract
OBJECTIVES Exercise induced bronchospasm (EIB) represents a common feature of childhood asthma which is most commonly revealed during free running. On the other hand aerobic exercise shows significant beneficial effects in asthmatics especially on the reduction of the level of systemic inflammation and is recommended as part of its treatment. The aim of this study was to test how mandatory mouth breathing influences the exercise induced level of decrease in lung function according to the level of severity of allergic rhinitis (AR). METHODS Free 6-minute running test preceded and followed by spirometry done with and without a nose clip a day apart was conducted in 55 children with moderate persistent asthma and AR. Children were divided into two groups according to the severity of nasal symptoms. RESULTS There was a greater fall in forced expiratory volume in one second after exercise with a nose clip in children with less nasal symptoms than in children with more nasal symptoms (mean ± SD; -5.28 (7.91) vs. -0.08 (4.58), p = 0.0228) compared to testing without the nose clip (mean ± SD; LNS, -1.31 ± 3.89%, p = 0.2408; MNS, -1.47 ± 3.68%, p = 0.2883). CONCLUSION Our results show that regular mouth breathing due to nasal congestion may lessen the degree of EIB in patients with persistent AR and allergic asthma.
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Affiliation(s)
- Mirjana Turkalj
- Reference Center for Clinical Pediatric Allergology of the Ministry of Health, Children's Hospital Srebrnjak, 10 000 Zagreb, Croatia; Faculty of Medicine, Josip Juraj Strossmayer University Osijek, Trg Svetog Trojstva 3, 31000 Osijek, Croatia
| | - Jelena Živković
- Reference Center for Clinical Pediatric Allergology of the Ministry of Health, Children's Hospital Srebrnjak, 10 000 Zagreb, Croatia.
| | - Marcel Lipej
- Reference Center for Clinical Pediatric Allergology of the Ministry of Health, Children's Hospital Srebrnjak, 10 000 Zagreb, Croatia
| | - Sandra Bulat Lokas
- Reference Center for Clinical Pediatric Allergology of the Ministry of Health, Children's Hospital Srebrnjak, 10 000 Zagreb, Croatia
| | - Damir Erceg
- Reference Center for Clinical Pediatric Allergology of the Ministry of Health, Children's Hospital Srebrnjak, 10 000 Zagreb, Croatia; Faculty of Medicine, Josip Juraj Strossmayer University Osijek, Trg Svetog Trojstva 3, 31000 Osijek, Croatia
| | - Srđan Ante Anzić
- Reference Center for Clinical Pediatric Allergology of the Ministry of Health, Children's Hospital Srebrnjak, 10 000 Zagreb, Croatia
| | - Robert Magdić
- Faculty of Kinesiology, Horvaćanski zavoj 15, 10 000 Zagreb, Croatia
| | - Davor Plavec
- Reference Center for Clinical Pediatric Allergology of the Ministry of Health, Children's Hospital Srebrnjak, 10 000 Zagreb, Croatia; Faculty of Medicine, Josip Juraj Strossmayer University Osijek, Trg Svetog Trojstva 3, 31000 Osijek, Croatia
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Dalbøge LS, Pedersen SL, Secher T, Holst B, Vrang N, Jelsing J. Neuromedin U inhibits food intake partly by inhibiting gastric emptying. Peptides 2015; 69:56-65. [PMID: 25895852 DOI: 10.1016/j.peptides.2015.04.010] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Revised: 03/31/2015] [Accepted: 04/07/2015] [Indexed: 12/21/2022]
Abstract
Neuromedin U (NMU) is a gut-brain peptide, implicated in energy and glucose homeostasis via the peripherally expressed NMU receptor 1 (NMUR1) and the central NMUR2. We investigated the effects of a lipidated NMU analog on gastric emptying (GE), glucose homeostasis and food intake to evaluate the use of a NMU analog as drug candidate for treatment of obesity and diabetes. Finally mRNA expression of NMU and NMUR1 in the gut and NMUR2 in the hypothalamus was investigated using a novel chromogen-based in situ hybridization (ISH) assay. Effects on food intake (6 and 18 h post dosing) were addressed in both mice and rats. The effects on GE and glycaemic control were assessed in mice, immediately after the first dose and after seven days of bidaily (BID) dosing. The lipidated NMU analog exerted robust reductions in GE and food intake in mice and improved glycaemic control when measured immediately after the first dose. No effects were observed after seven days BID. In rats, the analog induced only a minor effect on food intake. NMU mRNA was detected in the enteric nervous system throughout the gut, whereas NMUR1 was confined to the lamina propria. NMUR2 was detected in the paraventricular (PVN) and arcuate nuclei (ARC) in mice, with a reduced expression in ARC in rats. In summary, the anorectic effect of the lipidated NMU is partly mediated by a decrease in gastric emptying which is subject to tachyphylaxis after continuous dosing. Susceptibility to NMU appears to be species specific.
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Affiliation(s)
- Louise S Dalbøge
- Gubra ApS, Agern Alle 1, 2970 Hørsholm, Denmark; University of Copenhagen, The Novo Nordisk Foundation Center for Basic Metabolic Research, Blegdamsvej 3B, 2200 Copenhagen N, Denmark
| | | | | | - Birgitte Holst
- University of Copenhagen, The Novo Nordisk Foundation Center for Basic Metabolic Research, Blegdamsvej 3B, 2200 Copenhagen N, Denmark
| | - Niels Vrang
- Gubra ApS, Agern Alle 1, 2970 Hørsholm, Denmark
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McRorie JW, Kirby JA, Miner PB. Histamine 2-receptor antagonists: Rapid development of tachyphylaxis with repeat dosing. World J Gastrointest Pharmacol Ther 2014; 5:57-62. [PMID: 24868486 PMCID: PMC4023325 DOI: 10.4292/wjgpt.v5.i2.57] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/22/2013] [Revised: 01/10/2014] [Accepted: 03/04/2014] [Indexed: 02/06/2023] Open
Abstract
Histamine2-receptor antagonists (H2RAs) are available over-the-counter (OTC) for the treatment and prevention of heartburn, but more than occasional, single-dose use can lead to rapid development of tachyphylaxis. The aim of this review is to assess the published evidence regarding the development of tachyphylaxis with repeat usage of H2RAs. PubMed and SCOPUS were searched across all years to identify clinical studies that examined the development of tachyphylaxis with repeated dosing of H2RAs. Although a single (first) dose of an H2RA can be effective for controlling gastric acid and preventing or relieving food-related heartburn, numerous studies confirm that tachyphylaxis, also known as tolerance, is consistently detected at the first time point assessed after the first dose, including the second day and/or second dose. Even if symptom relief is achieved with an H2RA, it may be due to desensitization of the esophagus to acid exposure, potentially providing symptom relief without significantly decreasing esophageal acid exposure. When recommending OTC drugs for treatment of frequent heartburn, clinicians should be aware of the potential for rapid development of tachyphylaxis in patients who use H2RAs for 2 or more consecutive days. Even if symptom relief is achieved, it may be due to desensitization of the esophagus to acid by the H2RA, potentially providing symptom relief without significantly decreasing esophageal acid exposure. Other strategies, such as an OTC proton pump inhibitor, may be needed to optimize management of frequent heartburn.
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Zhang Y, Collazo R, Gao Y, Li G, Scarpace PJ. Intermittent MTII application evokes repeated anorexia and robust fat and weight loss. Peptides 2010; 31:639-43. [PMID: 20034526 PMCID: PMC2860181 DOI: 10.1016/j.peptides.2009.12.019] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/12/2009] [Revised: 12/12/2009] [Accepted: 12/13/2009] [Indexed: 10/20/2022]
Abstract
Central melanocortins (MC) evoke potent but transient anorectic responses with tachyphylaxis developing within days. We hypothesized that intermittent therapy using the MC analog, melanotan II (MTII), would minimize the tachyphylaxis and enhance the long-term efficacy of MTII treatment. F344/BN rats were infused with MTII or vehicle into the lateral ventricle by mini pump for 14 days. Half the MTII-infused rats were then given vehicle (MTII-On/Off), while the remaining received fresh MTII (MTII-On) for 10 days. Finally, pumps in both groups were replaced with ones containing fresh MTII for an additional 6 days. The first MTII application induced a 30% food reduction that attenuated within 5 days. Reapplication of MTII in MTII-On/Off rats, after the off period, invoked a new and equally robust anorectic response while continuation of MTII supplement in the MTII-On group did not change food intake from the control level. Body weights decreased similarly in both MTII groups at termination (day 30). Hypothalamic MC3 receptor, AgRP, and POMC expressions were unchanged, but MC4 receptor expression was diminished by 25%, and adiposity reduced by 80% in both MTII groups. Acetyl-CoA carboxylase 1 phosphorylation was elevated in perirenal fat by over 10 fold with either MTII treatment. In conclusion, intermittent MTII treatment preserves anorectic responses but does not prevent tachyphylaxis, whereas constant MTII application blunts further food response after the initial tachyphylaxis. Either form of MTII administration results in significant weight and adiposity reductions, involving perhaps fatty acid oxidation within specific adipose tissues.
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Affiliation(s)
- Yi Zhang
- Research Department, Malcom Randall Veterans Affairs Medical Center-NF/SG HSC, Rm E585-1, 1601 SW Archer Road, Gainesville, FL 32608, USA.
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