Bismuth chelate

It has been demonstrated that monoclonal antibodies may be chemically modified by reaction with metal chelates without loss of antibody activity or specificity. A radionuclide generator has been made to provide a source for Bi-212 to be used for attachment of bismuth chelates to antibody. Such antibody-metal-chelate conjugates appear to be stable in vivo and may provide a new method for radiotherapy. 

Milk and dairy foods decrease the absorption of some tetracyclines (doxycycline and minocycline are not affected), some quinolone antibiotics (absorption of ciprofloxacin and norfloxacin is decreased but ofloxacin is not affected), penicillamine and alendronate. Large volumes of milk can reduce the ulcer-healing properties of bismuth tripotassium dicitratobismuthate (bismuth chelate),... 

Hekobocter pylori anioxicillin + clarithromycin + metronidazole amoxicillin + metronidazole + bismuth chelate... 

Tripotassium dicitratobismuthate, bismuth subcitrate, (De-Nol) This substance was originally thought to act mainly by chelating with protein in the ulcer base to form a coating, which protects the ulcer from the adverse influences of acid, pepsin and bile. Subsequently, bismuth chelate was found to possess an additional valuable action, namely activity against Helicobacter pylori, especially when combined with an antimicrobial (see below). 

Bismuth chelate is used for benign gastric and duodenal ulcer and has a therapeutic efficacy approximately equivalent to histamine receptor antagonists. Ulcers remain healed for longer after bismuth chelate than after the histamine receptor antagonists, and this may relate to the ability of the former but not the latter to eradicate Helicobacter pylori. 

Adverse effects. Bismuth chelate, particularly as a liquid formulation, darkens the tongue, teeth and stool the effect is less likely with the tablet, which is thus more acceptable. There is little systemic absorption of bismuth from the chelated preparation, but bismuth is excreted by the kidney and it is prudent to avoid giving the drug to patients with impaired renal fimction. Urinary elimination continues for months after bismuth is discontinued. 

Bismuth-containing antacid preparations have been in use for a long time, but some of the bismuth chelates (e.g. tripotassium dicitratobismuthate) are of proven benefit in ulcer, and, though it is not clear how they work, there is some... 

Sucralfate polymerizes below pH 4 to give a very. sticky gel that adheres strongly to the ba.se of ulcer craters. Bismuth chelate may act in a simitar way to sucralfate. It has a strong aflinity for mucosal glycoproteins, especially in the necrotic tissue of the ulcer craters, which become coaled in a protective layer of polymer-glycoprotein complex. Bismulh ntay blacken the icelh and stools. Bismuth and sucralfate must be given on an emply stomach or they will complex with food proteins. 

Neither 10 mL of Maalox (aluminium/magnesium hydroxide) nor 10 g of Solugastril (aluminium hydroxide with calcium carbonate) had any effect on the pharmacokinetics of a 4-mg lomoxicam film-coated tablet in 18 healthy fasted subjects. A later study similarly found no changes in the absorption or pharmacokinetics of a lomoxicam film-coated tablet given with bismuth chelate (tripotassium dicitratobismuthate) 120 mg twice daily. There would seem to be no reason for avoiding concurrent use. 

Ravic M, Jdmston A, Turner P, Foley K, Rosenow D Does bismuth chelate influence lomoxicam absorption /fum Toxicol( 997) 11,59-60. 

Direct Titrations. The most convenient and simplest manner is the measured addition of a standard chelon solution to the sample solution (brought to the proper conditions of pH, buffer, etc.) until the metal ion is stoichiometrically chelated. Auxiliary complexing agents such as citrate, tartrate, or triethanolamine are added, if necessary, to prevent the precipitation of metal hydroxides or basic salts at the optimum pH for titration. Eor example, tartrate is added in the direct titration of lead. If a pH range of 9 to 10 is suitable, a buffer of ammonia and ammonium chloride is often added in relatively concentrated form, both to adjust the pH and to supply ammonia as an auxiliary complexing agent for those metal ions which form ammine complexes. A few metals, notably iron(III), bismuth, and thorium, are titrated in acid solution. 

The oxidation state +3 of bismuth is of primary interest for radiotherapy applications. As such, various polyaminocarboxylate ligands have been investigated as chelates for 212Bi and 213Bi. 

Rodionova and Ivanov [667] used chelate extraction in the determination of copper, bismuth, lead, cadmium, and zinc in seawater. The metal complexes of diethyl and dithiophosphates are extracted in carbon tetrachloride prior to determination by atomic absorption spectrometry. 

Bi-0 2.54(l)-2.68(2) A], In contrast, the nine-coordinate capped square antiprism geometry for bismuth in [Bi(N03)3(H20)3] (18-crown-6) does not involve the expected multidentate ether coordination to bismuth, but rather a hydrogen-bonded interaction of the crown ether with the hydrated bismuth center chelated by bidentate nitrate groups [Bi-0 2.38(2)—2.56(2) A] 32, implying that the hexado-... 

Complexes of bismuth chloride with 2 equiv of the AT,AT-substituted dithioxamide ligands of the general formulas [BiCl3 RNHC(S)C(S) NHR 2] (R = Me, Et, Pr, nBu, CH2Ph) likely involve five-membered chelate interactions (123) as demonstrated by the structurally characterized example [BiCl3 EtNHC(S)C(S)NHEt 2] Me2CO, which involves a seven-coordinate pentagonal bipyramidal environment for bismuth (124), with chlorine atoms in axial positions [Bi-Cl 2.635(10) and 2.717(1) A] and one equatorial [Bi-Cl 2.651(12) A] with four sulfur centers [Bi-S 2.818(13)-3.042(12) A],... 

A variety of derivatives of bis-[Bi(tr)2X, X = Cl or N03], tris-(Bitr3), and tetra-([Bi(tr)4X][Na]) tropolonate complexes of bismuth (178, 179) have been prepared and spectroscopically characterized (176, 177, 180). Solid-state structures for examples of bis-(tropolonate) derivatives confirm the chelate interaction (171) and in the case of the nitrate derivative, reveal intermolecular alkoxide-bismuth [Bi-0 2.688 and 2.666 A] dimer contacts 52, which are slightly longer than the chelate bonds [Bi-0 2.130-2.323 A],... 

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