Formulation in Pharmacy Practice   2nd Edition

NORFLOXACIN
 
 
Norfloxacin is very slightly soluble in water and alcohol.  The drug is relatively insoluble in water at neutral pH but solubility increases in acidic and basic conditions.  Norfloxacin eye drops are formulated as a solution at a pH of about 5.2.

The preparation of norfloxacin suspension from tablets is not recommended unless a full assessment of physical stability can be performed.  Boonme et al determined that the physical properties of norfloxacin suspensions are influenced by the brand of tablet used.1

Tablet dispersion in plain water is the best option.  The method for the Noroxin® brand of norfloxacin is as follows:
  • Break the scored tablet and add to 10 - 15mL of water in a wide bottomed glass or cup.
  • Leave for 10 - 15 minutes, swirling occasionally.  A coarse chalky suspension is formed.
  • The mixture has a slight bitter aftertaste and can be mixed with fruit cordial or chocolate milk prior to administering the dose.
  • Tablet dispersions should be used immediately.
NB This method is not suitable for doses smaller than a measurable tablet fraction as the drug
is not in solution.

Formula 1

Norfloxacin Suspension 20mg per mL
 
Norfloxacin tablets  400mg  
Water 15  mL
*Vehicle to   100  mL
 
Expiry:  30 days.
 
Storage:  Room temperature.  Protect from light (amber glass containers used in the study).
 
Shake well before use
 

 
NOTES
  1. *Formula for the vehicle:
    Tragacanth g
    Saccharin sodium g
    Sorbitol solution 100  mL
    Glycerol 100  mL
    Parabens 0.1  %
    Peppermint spirit BP 30  mL
    Water 300  mL
    Syrup BP to   1000  mL

  2. The brands of norfloxacin tablets used in the study were not described.  Some brands may produce a dispersible and pourable product, but others produce a liquid that is gel like and too viscous to pour.  This is likely to be due to a physical interaction between tablet excipients and components of the base.1
  3. Other vehicles could be investigated, for example a simple mixture of syrup and glycerin.  Physical stability should be evaluated.

REFERENCE
  1. Boonme P, Phadoongsombut N, Phoomborplub P, Viriyasom S.  Stability of extemporaneous norfloxacin suspension.  Drug Dev Ind Pharm 2000; 26 (7): 777-9.

 
Formulation in Pharmacy Practice
2nd Edition