These are aromatic diamidine antiseptics that are bactericidal against Gram-positive but less active against Gram-negative bacteria. They have been available as P medicines for many years, but the BNF regards them as of little value in bacterial infections.

Eye drops are formulated with propamidine isetionate 0.1 per cent and eye ointment with dibrompropamidine isetionate 0.15 per cent. Both can be used for adults and children.

Dosage

The ointment persists longer on the corneal surface than drops and needs to be applied only twice daily, but can cause stickiness and blurring of vision. It is suitable for the treatment of both conjunctivitis and styes.

Drops need to be used four times daily and are not suitable for styes. Probably the best regimen for conjunctivitis is to use drops during the day and ointment at night. In both conditions, treatment should be continued for 24 hours after symptoms have cleared. If symptoms do not significantly improve within 48 hours, treatment should be discontinued and the patient referred for medical advice.

Side effects and cautions

• Both formulations may cause slight stinging when applied.
• Contact lenses should not be worn when either preparation is being used.
• As with all ophthalmic preparations, products should be discarded not more than one month after opening.