Convulsive Seizure Due to Hypomagnesemia Caused by Short-term Vonoprazan Intake

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Abstract

A 71-year-old woman was admitted for the treatment of diffuse large B-cell lymphoma of the ileum. She had been taking lansoprazole but was switched to vonoprazan due to epigastric discomfort. Three weeks after starting vonoprazan intake, she had a convulsive seizure, and a blood test showed hypomagnesiemia. The cause of hypomagnesemia was considered to be malabsorption of magnesium from the intestinal tract associated with vonoprazan. After discontinuation of vonoprazan, the magnesium level quickly recovered, and the seizures did not relapse. It is important to consider the risk of hypomagnesemia in patients taking vonoprazan, even for a short period of time.

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Acid-inhibitory effects of vonoprazan 20 mg compared with esomeprazole 20 mg or rabeprazole 10 mg in healthy adult male subjects--a randomised open-label cross-over study.

Y. Sakurai, Rodrigo Mori, H Okamoto … (2015)

Proton pump inhibitors (PPIs) are widely used for the treatment of acid-related diseases. Vonoprazan is a member of a new class of acid suppressants; potassium-competitive acid blockers. Vonoprazan may thus be an alternative to PPIs.

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Potentiation of TRPM7 Inward Currents by Protons

Jianmin Jiang, MINGJIANG LI, Lixia Yue (2005)

TRPM7 is unique in being both an ion channel and a protein kinase. It conducts a large outward current at +100 mV but a small inward current at voltages ranging from −100 to −40 mV under physiological ionic conditions. Here we show that the small inward current of TRPM7 was dramatically enhanced by a decrease in extracellular pH, with an ∼10-fold increase at pH 4.0 and 1–2-fold increase at pH 6.0. Several lines of evidence suggest that protons enhance TRPM7 inward currents by competing with Ca2+ and Mg2+ for binding sites, thereby releasing blockade of divalent cations on inward monovalent currents. First, extracellular protons significantly increased monovalent cation permeability. Second, higher proton concentrations were required to induce 50% of maximal increase in TRPM7 currents when the external Ca2+ and Mg2+ concentrations were increased. Third, the apparent affinity for Ca2+ and Mg2+ was significantly diminished at elevated external H+ concentrations. Fourth, the anomalous-mole fraction behavior of H+ permeation further suggests that protons compete with divalent cations for binding sites in the TRPM7 pore. Taken together, it appears that at physiological pH (7.4), Ca2+ and Mg2+ bind to TRPM7 and inhibit the monovalent cationic currents; whereas at high H+ concentrations, the affinity of TRPM7 for Ca2+ and Mg2+ is decreased, thereby allowing monovalent cations to pass through TRPM7. Furthermore, we showed that the endogenous TRPM7-like current, which is known as Mg2+-inhibitable cation current (MIC) or Mg nucleotide–regulated metal ion current (MagNuM) in rat basophilic leukemia (RBL) cells was also significantly potentiated by acidic pH, suggesting that MIC/MagNuM is encoded by TRPM7. The pH sensitivity represents a novel feature of TRPM7 and implies that TRPM7 may play a role under acidic pathological conditions.

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Characterization of a novel potassium-competitive acid blocker of the gastric H,K-ATPase, 1-[5-(2-fluorophenyl)-1-(pyridin-3-ylsulfonyl)-1H-pyrrol-3-yl]-N-methylmethanamine monofumarate (TAK-438).

J Shin, N Inatomi, K Munson … (2011)

Inhibition of the gastric H,K-ATPase by the potassium-competitive acid blocker (P-CAB) 1-[5-(2-fluorophenyl)-1-(pyridin-3-ylsulfonyl)-1H-pyrrol-3-yl]-N-methylmethanamine (TAK-438), is strictly K(+)-competitive with a K(i) of 10 nM at pH 7. In contrast to previous P-CABs, this structure has a point positive charge (pK(a) 9.06) allowing for greater accumulation in parietal cells compared with previous P-CABs [e.g., (8-benzyloxy-2-methyl-imidazo(1,2-a)pyridin-3-yl)acetonitrile (SCH28080), pK(a) 5.6]. The dissociation rate of the compound from the isolated ATPase is slower than other P-CABs, with the t(1/2) being 7.5 h in 20 mM KCl at pH 7. The stoichiometry of binding of TAK-438 to the H,K-ATPase is 2.2 nmol/mg in the presence of Mg-ATP, vanadate, or MgP(i). However, TAK-438 also binds enzyme at 1.3 nmol/mg in the absence of Mg(2+). Modeling of the H,K-ATPase to the homologous Na,K-ATPase predicts a close approach and hydrogen bonding between the positively charged N-methylamino group and the negatively charged Glu795 in the K(+)-binding site in contrast to the planar diffuse positive charge of previous P-CABs. This probably accounts for the slow dissociation and high affinity. The model also predicts hydrogen bonding between the hydroxyl of Tyr799 and the oxygens of the sulfonyl group of TAK-438. A Tyr799Phe mutation resulted in a 3-fold increase of the dissociation rate, showing that this hydrogen bonding also contributes to the slow dissociation rate. Hence, this K(+)-competitive inhibitor of the gastric H,K-ATPase should provide longer-lasting inhibition of gastric acid secretion compared with previous drugs of this class.

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Journal

Journal ID (nlm-ta): Intern Med

Journal ID (iso-abbrev): Intern Med

Title: Internal Medicine

Publisher: The Japanese Society of Internal Medicine

ISSN (Print): 0918-2918

ISSN (Electronic): 1349-7235

Publication date (Electronic): 17 July 2021

Publication date (Print): 15 January 2022

Volume: 61

Issue: 2

Pages: 237-240

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[1 ]Department of Hematology, Hakodate Municipal Hospital, Japan

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Correspondence to Dr.　Masayuki Aiba, aiba.masa37@ 123456gmail.com

Article

DOI: 10.2169/internalmedicine.7758-21

PMC ID: 8851186

PubMed ID: 34275986

SO-VID: cbf112fb-4e1f-4c88-8825-42694f12b487

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The Internal Medicine is an Open Access journal distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License. To view the details of this license, please visit ( https://creativecommons.org/licenses/by-nc-nd/4.0/).

Convulsive Seizure Due to Hypomagnesemia Caused by Short-term Vonoprazan Intake

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Most cited references 16

Acid-inhibitory effects of vonoprazan 20 mg compared with esomeprazole 20 mg or rabeprazole 10 mg in healthy adult male subjects--a randomised open-label cross-over study.

Potentiation of TRPM7 Inward Currents by Protons

Characterization of a novel potassium-competitive acid blocker of the gastric H,K-ATPase, 1-[5-(2-fluorophenyl)-1-(pyridin-3-ylsulfonyl)-1H-pyrrol-3-yl]-N-methylmethanamine monofumarate (TAK-438).

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