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Category  Antibacterial.

        Dicloxacillin Sodium Capsules contain not less than 90.0 per cent and not more than 120.0 per cent of the labelled amount of dicloxacillin (C₁₉H₁₇Cl₂N₃O₅S).

Strength available  250 mg and 500 mg (base).

Dose  Dosage of Dicloxacillin Sodium Capsules is expressed in terms of dicloxacillin base.
     Adults and children 40 kg of body weight and over:  125 to 500 mg every 6 hours.
     Children up to 40 kg of body weight:  3.125 to 6.25 mg per kg of body weight every 6 hours.
Contra-indication; Warning; Precaution; Additional information  See under Dicloxacillin Sodium.

Packaging and storage  Dicloxacillin Sodium Capsules shall be kept in tightly closed containers and stored at a temperature not exceeding 30°. 

Labelling  The label on the container states (1) the quantity equivalent to the amount of dicloxacillin; (2) the expiration date.

Identification  The retention time of the major peak in the chromatogram of the Assay preparation corresponds to that of the Standard preparation, as obtained in the Assay.

Water  Not more than 5.0 per cent w/w (Karl Fischer Method, Appendix 4.12).

Dissolution  Carry out the test as described in the “Dissolution Test” (Appendix 4.24).
     Dissolution medium:  water; 900 mL.
     Apparatus 1:  100 rpm.
     Time:  30 minutes.
     Determine the amount of dicloxacillin dissolved using the following method.
     Mobile phase and Chromatographic system  Prepare as directed in the Assay.
     Standard solution  Weigh accurately a suitable quantity of Dicloxacillin Sodium RS, dissolve in and dilute with Dissolution medium to obtain a solution having a known concentration of about 280 µg per mL of dicloxacillin sodium.  Filter through a 0.45-µm membrane filter and use the filtrate.  (Note  Use the standard solution promptly, or refrigerate and use on the day prepared.)
     Test solution  If necessary, dilute a filtered portion of the test solution with Dissolution medium to obtain a solution having a concentration of about 280 µg of dicloxacillin sodium per mL, and mix.
    Procedure  Inject about 6 µL each of Standard solution and Test solution into the chromatograph, record the chromatogram, and measure the response for the major peak. 
    Calculation  Calculate the quantity of C₁₉H₁₇Cl₂N₃O₅S dissolved by comparing this peak response with the major peak response similarly obtained on chromatographing Standard solution.
    Tolerances Not less than 75 per cent (Q) of the labelled amount of C₁₉H₁₇Cl₂N₃O₅S is dissolved in 30 minutes.
Assay  Carry out the determination as described in the “Liquid Chromatography” (Appendix 3.5).
     Buffer  Prepare a solution containing 2.72 mg per mL of monobasic potassium phosphate, adjusted with 8 M potassium hydroxide to a pH of 4.9 to 5.1.
     Standard preparation  Weigh accurately a suitable quantity of Dicloxacillin Sodium RS, dissolve in and dilute with Buffer to obtain a solution containing about 1.1 mg per mL of Dicloxacillin Sodium.  Filter through a 0.45-µm membrane filter and use the filtrate.  (Note  Use the standard preparation promptly, or refrigerate and use on the day prepared.)
     Assay preparation  Remove, as completely as possible, the contents of not less than 10 Dicloxacillin Sodium Capsules and weigh accurately.  Mix the combined contents, and transfer an accurately weighed quantity, containing about 50 mg of dicloxacillin, to a 50-mL volumetric flask.  Add 30 mL of Buffer, sonicate for 5 minutes, and dilute with Buffer to volume.  Filter through a 0.45-µm membrane filter and use the filtrate.  (Note  Use the assay preparation promptly, or refrigerate and use on the day prepared.)
    Mobile phase  Acetonitrile and Buffer (1:3)
    Chromatographic System
     DETECTOR  Ultraviolet light (225 nm).
     COLUMN  A stainless steel column (15 cm × 4.6 mm), packed with octadecylsilane chemically bonded to porous silica or ceramic microparticles (5 µm).
     FLOW RATE  2.0 mL per minute
System Suitability
     Sample  Standard preparation
Suitability requirements
     CAPACITY FACTOR  Between 4 and 11 for the dicloxacillin peak.
     COLUMN EFFICIENCY  Not less than 700 theoretical plates for the dicloxacillin peak.
     SYMMETRY FACTOR  Not more than 2.0 for the dicloxacillin peak.
     RELATIVE STANDARD DEVIATION  Not more than 2.0 per cent for the dicloxacillin peak.
Procedure  Separately inject equal volumes (about 2 mL) of Standard preparation and Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. 
Calculation  Calculate the content of C₁₉H₁₇Cl₂N₃O₅S in the portion of the Capsules taken, using the declared content of C₁₉H₁₇Cl₂N₃O₅S in Dicloxacillin Sodium RS.

Other requirements  Comply with the requirements described under “Capsules” (Appendix 1.16).