Stabilization of radiopharmaceutical compositions using ascorbic acid

Abstract

Radiopharmaceutical compositions, and related methods, useful for medical imaging are provided. The radiopharmaceutical compositions include one or more radiopharmaceutical compounds, together with a stabilizer comprising ascorbic acid, wherein the pH of said composition is within the range of about 3.5-5.5.

What is claimed is: 
     
         1 - 19 . (canceled) 
     
     
         20 . A method for preparing a composition, comprising:
 adding a first solution comprising a radiopharmaceutical compound to a second solution comprising ascorbic acid within a pH range of about 3.5-5.5, to form a third solution comprising the radiopharmaceutical compound and ascorbic acid.   
     
     
         21 . The method of  claim 20 , wherein said pH is within the range of about 4-5. 
     
     
         22 . The method of  claim 20 , wherein said pH is within the range of about 4-4.5. 
     
     
         23 . The method of  claim 20 , wherein the radiopharmaceutical compound is purified by chromatography, prior to addition of the first solution to the second solution. 
     
     
         24 . The method of  claim 20 , wherein the radiopharmaceutical compound is not purified by chromatography, prior to addition of the first solution to the second solution. 
     
     
         25 . The method of  claim 20 , further comprising the step of adjusting the pH of the third solution to about 6-8, after addition of the first solution to the second solution. 
     
     
         26 . The method of  claim 20 , wherein said radiopharmaceutical compound is at least one member selected from the group consisting of rotenone, pyridaben, fenazaquin, fenpyroximate, tebufenpyrad, piericidins, and 2-substituted chromones, and analogs thereof. 
     
     
         27 . The method of  claim 26 , wherein said radiopharmaceutical compound is at least one member selected from the group consisting of pyridaben and analogs thereof. 
     
     
         28 . The method of  claim 27 , wherein said radiopharmaceutical compound is at least one member selected from the group consisting of compounds containing a 2-alkyl-4-chloro-2H-pyridazin-3-one with a lipophilic side chain substituted at the 5-position. 
     
     
         29 . The method of  claim 28 , wherein said radiopharmaceutical compound is 2-tert-Butyl-4-chloro-5-[4-(2-[ 18 F]fluoro-ethoxymethyl)-benzyloxy]-2H-pyridazin-3-one. 
     
     
         30 . The method of  claim 20 , wherein said radiopharmaceutical compound is labeled with a radioisotope. 
     
     
         31 . The method of  claim 30 , wherein said radioisotope is selected from the group consisting of  11 C,  13 N,  18 F,  86 Br,  124 I,  125 I, and  131 I. 
     
     
         32 . The method of  claim 31 , wherein said radioisotope is selected from the group consisting of  11 C,  13 N, and  18 F. 
     
     
         33 . The method of  claim 32 , wherein said radioisotope is  18 F. 
     
     
         34 . The method of  claim 20 , wherein the composition comprises greater than about 50 mg of ascorbic acid per milliliter, the method further comprising the step of adjusting the pH of the third solution to about less than 6, after addition of the first solution to the second solution. 
     
     
         35 - 36 . (canceled) 
     
     
         37 . A method, comprising:
 administering to a patient a composition comprising 2-tert-butyl-4-chloro-5-[4-(2-[ 18 F]fluoro-ethoxymethyl)-benzyloxy]-2H-pyridazin-3-one, ascorbic acid in an amount greater than about 50 mg of ascorbic acid per milliliter, wherein the composition has a pH that is less than about 6.   
     
     
         38 . (canceled) 
     
     
         39 . A method for preparing a composition, comprising:
 adding a first solution comprising 2-tert-butyl-4-chloro-5-[4-(2-[ 18 F]fluoro-ethoxymethyl)-benzyloxy]-2H-pyridazin-3-one to a second solution comprising ascorbic acid, wherein the second solution has a pH within the range of about 4-4.5 and comprises greater than about 50 mg of ascorbic acid per milliliter, to form a third solution comprising 2-tert-butyl-4-chloro-5-[4-(2-[ 18 F]fluoro-ethoxymethyl)-benzyloxy]-2H-pyridazin-3-one and ascorbic acid.