The Pharmaceutics and Compounding Laboratory
Ophthalmic Preparations

Laboratory Procedure

Experimental Procedure and Data (Have all calculations ready for TA to check at the beginning of lab).

1. Buffers and Buffer Capacity

  • Using dibasic potassium phosphate (K2HPO4) and monobasic potassium phosphate (KH2PO4), prepare 500 ml of a buffer solution at pH 7.4 with a buffer capacity of 0.05.

  • Using a pH meter, measure the pH of 100 ml of the solution.

  • Titrate 100 ml of the solution with 1 N NaOH until the pH increases by one unit and determine whether the buffer capacity is as calculated. Note that the exact normality of the NaOH solution may vary with available stock solutions; note and record the exact normality of the reagent you use in the experiment.

  • Calculate the buffer capacity as:

      = gram equivalent of strong acid/base to change pH of 1 liter of buffer solution

      = the pH change caused by the addition of strong acid/base

    Calculations:

      MW K2HPO4 _________________

      MW KH2PO4 _________________

      Ka ________________

      pKa _______________

      K2HPO4 = __________ g

      KH2PO4 = __________ g

    Data and Results:

      Measured beginning pH _______

      Volume of ____N NaOH added to 100 ml to change pH by 1 unit = _________

      Eq NaOH added _______

      Measured buffer capacity _______

2. Isotonicity and Sterility

Use the NaCl equivalent method and appropriate compounding techniques to prepare the following sterile, isotonic ophthalmic solution.

                     I. Ben Hadd, M.D.          Rx# 51801
                     123 Downda Road
                     Anywhere, NC 27000

Phone: 929-0987                    DEA# AH 12345678

Name:   James Pool                  Date:   Today  
Address: 11 Park Place, Chapel Hill Phone:  555-1234 

Rx
  Procaine HCl          1.5 %
  Benzalkonium chloride 1:10,000
  Boric Acid q.s.
  Aqua. dest. q.s. ad 60 ml

  M.Ft. Sterile, isotonic solution
  Sig. gtts ii o.u. t.i.d.
                                                   
 Product Selection Permitted    Dispense as written

    Procaine HCl _______________________ g (E = ___________ )

    Benzalkonium chloride _______________ g (E = ___________ )

    Boric Acid _________________________ g (E = ___________ )

    Benzalkonium chloride 1:1,000 solution needed __________________ ml

    Calculations:

    Compounding Procedure:

    Therapeutic use: ___________________________________

    Measured osmolality ________________________________ (mmol/Kg)

3. Isotonicity and pH Adjustment

Prepare the following prescription.

                             I. Ben Hadd, M.D.                     Rx# 51802
                             123 Downda Road
                             Anywhere, NC 27000

Phone: 929-0987                              DEA# AH 12345678

Name:   Perma Bond                         Date:   Today  
Address: 11 Yellow Brick Rd, Chapel Hill   Phone:  555-1234 

Rx
  Ampicillin Sodium         30 mg/ml
  Sodium chloride q.s. 

  M.Ft. 15 ml of sterile, buffered, isotonic solution at pH 6.6
  Sig. gtts ii o.u. t.i.d.
                                                   
 Product Selection Permitted    Dispense as written

      Ampicillin sodium ______________________ g (E = _____________)

      Sodium chloride _______________________ g

      Monobasic sodium phosphate, anhydrous (NaH2PO4) 0.0667 M solution needed ____________ ml

      Dibasic sodium phosphate, anhydrous (Na2HPO4) 0.0667 M solution needed _______________ ml

    Calculations:

    Compounding Procedure:

    Therapeutic use: ___________________________

    Measured osmolality _____________________ (mmol/Kg)

4. Isotonicity and pH Adjustment (continued)

Make calculations to prepare the following prescription as a buffered isotonic solution at pH = 5.9. Describe how you would prepare the solution using 500 mg/vial Vancomycin Sulfate powder for injection (when reconstituted with 9.7 ml sterile water for injection makes a 50 mg/ml solution), Sodium Chloride 30% (concentrate) for injection, and stock solutions of 0.0667 M NaH2PO4and 0.0667 M Na2HPO4. Do not prepare.

                         I. Ben Hadd, M.D.              Rx # 51803
                         123 Downda Road
                         Anywhere, NC 27000

Phone:  929-0987                           DEA # AH 12345678

Name:  Ima Bored                      Date:   Today  
Address:  11 Brick Road, Chapel Hill  Phone: 555-4567 

Rx
  Vancomycin sulfate  30 mg/ml
  Sodium chloride q.s.
  Monobasic sodium phosphate q.s.
  Dibasic sodium phosphate q.s.

   M.Ft. 15 ml of sterile, buffered, isotonic solution at pH 5.9
   Sig. gtts ii o.u. t.i.d.
                                                     
  Product Selection Permitted     Dispense as written

    Vancomycin sulfate ________________________ mg    (E = __________)

    Monobasic sodium phosphate, anhydrous (NaH2PO4) 0.0667 M solution needed __________________ ml

    Dibasic sodium phosphate, anhydrous (Na2HPO4) 0.0667 M solution needed __________________ ml

    Sodium chloride (30%) concentrate needed _____________ ml

    Calculations:

    Compounding Procedure:

    Therapeutic use: ____________________________

    Label _____________________________