Rifabutin
;)
(9S,12E,14S,15R,16S,17R,18R,19R,20S,21S,22E,24Z)-6,16,18,20-Tetrahydroxy-1¢-isobutyl-14-methoxy-7,9,15,17,19,21,25-heptamethylspiro[9,4-(epoxypentadeca[1,11,13]trienimino)-2H-furo[2¢,3¢:7,8]naphth[1,2-d]imidazole-2,4¢-piperidine]-5,10,26-(3H,9H)-trione-16-acetate [72559-06-9].
»Rifabutin contains not less than 950µg and not more than 1020µg of C46H62N4O11per mg,calculated on the anhydrous basis.
Packaging and storage—
Preserve in well-closed containers,protected from light and from excessive heat.
Identification—
A:
Infrared Absorption á197Kñ.
B:
The retention time of the major peak in the chromatogram of the Assay preparationcorresponds to that in the chromatogram of the Standard preparationobtained as directed in the Assay.
Water,Method Iá921ñ:
not more than 2.5%.
Limit of N-isobutylpiperidone—
Prepare a test solution of Rifabutin in a mixture of chloroform and methanol (1:1)containing 10mg per mL.Prepare a series of Standard solutions of N-isobutylpiperidone in a mixture of chloroform and methanol (1:1)containing 0.005,0.01,0.02,0.05,and 0.1mg per mL,respectively.Separately apply 10-µLspots of the test solution and the Standard solutions to the starting line of a thin-layer chromatographic plate (see Chromatography á621ñ)coated with a 0.25-mm layer of chromatographic silica gel mixture,and allow to dry.Develop the chromatograms in a solvent system consisting of a mixture of hexanes and acetone (100:30)in an equilibrated unlined chromatographic chamber until the solvent front has moved about three-fourths of the length of the plate.Remove the plate from the chromatographic chamber,allow the plate to air-dry,and place it in an iodine vapor chamber until the spots are visible (about 5minutes).Remove the plate from the chamber,spray the plate with starch TS,and examine the plate:no spot in the chromatogram of the test solution at an RFvalue corresponding to that of N-isobutylpiperidone is more intense than that of the principal spot observed in the chromatogram obtained from the Standard solution containing 0.05mg of N-isobutylpiperidone per mL(0.5%).
Chromatographic purity—
Using the chromatogram of the Assay preparationobtained as directed in the Assay,calculate the percentage of impurities by the formula:
100(ri/rS),
in which riis the response of an individual impurity and rSis the sum of the responses of all peaks:any impurity peak detected at a retention time of about 0.5,0.6,0.8,or 1.4relative to the retention time of the rifabutin peak does not exceed 1.0%,not more than 0.5%of any other impurity is detected,and the total of all impurity peaks is not more than 3.0%.
Assay—
0.1M Monobasic potassium phosphate—
Prepare a solution containing 13.6g of monobasic potassium phosphate per liter.
Mobile phase—
Prepare a mixture of acetonitrile and 0.1M Monobasic potassium phosphate(50:50).Adjust by dropwise addition of 2Nsodium hydroxide to a pHof 6.5±0.1.Filter through a 0.5-µm or finer porosity filter,and degas.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).
Standard preparation—
Transfer about 25mg of USP Rifabutin RS,accurately weighed,to a 50-mLvolumetric flask.Add 5mLof acetonitrile,dilute with Mobile phaseto volume,and mix.
Assay preparation—
Transfer about 25mg of Rifabutin,accurately weighed,to a 50-mLvolumetric flask.Add 5mLof acetonitrile,dilute with Mobile phaseto volume,and mix.
Resolution solution—
Dissolve about 10mg of Rifabutin and 2mLof methanol,add 1mLof 2Nsodium hydroxide,and allow to stand for about 4minutes.Add 1mLof 2Nhydrochloric acid,and dilute with Mobile phaseto 50mL.[NOTE—Portions of this solution may be stored in the frozen state for future use.]
Chromatographic system
(see Chromatography á621ñ)—The liquid chromatograph is equipped with a 254-nm detector and a 4.6-mm ×12.5-cm column that contains 5-µm diameter packing L7.The flow rate is about 1mLper minute.Chromatograph the Resolution solution,and record the peak responses as directed for Procedure:the chromatogram exhibits a major peak for a degradant,two minor peaks for degradants,and a major peak for rifabutin at relative retention times of about 0.5,0.6,0.8,and 1.0,respectively.The resolution,R,between the rifabutin peak and the degradant peak eluting at a relative retention time of about 0.8is not less than 1.3.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the column efficiency is not less than 2000theoretical plates,and the relative standard deviation for replicate injections is not more than 2.0%.
Procedure—
Separately inject equal volumes (about 10µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms for a period of time that is twice the retention time of the major rifabutin peak,and measure the area responses for the major peaks.Calculate the quantity,in µg,of C46H62N4O11in each mg of Rifabutin taken by the formula:
50(CP/W)(rU/rS),
in which Cis the concentration,in mg per mL,of USP Rifabutin RSin the Standard preparation,Pis the designated potency,in µg per mg,of USP Rifabutin RS,Wis the weight,in mg,of Rifabutin taken to prepare the Assay preparation,and rUand rSare the rifabutin peak area responses obtained from the Assay preparationand the Standard preparation,respectively.
Auxiliary Information—
Staff Liaison:William W.Wright,Ph.D.,Scientific Fellow
Expert Committee:(PA7)Pharmaceutical Analysis 7
USP28–NF23Page 1725
Phone Number:1-301-816-8335