The treatment of
Acanthamoeba keratitis has now been possible since the first successful therapy developed in the mid 1980s with a combination of
propamidine 0.1% (
Brolene) and
neomycin 1%. However, only half the patients responded to this regimen as the
cysts were often resistant to
neomycin and relatively insensitive to
propamidine. This led to research for better
therapy, culminating in the mid 1990s with research in Glasgow demonstrating much increased effectiveness with use of the
biguanide chlorhexidine 0.02% and in London and Bristol for similar effectiveness with the polymeric
polyhexamethylene biguanide (PHMB) 0.02%. Both
biguanides were combined with
propamidine for enhanced effectiveness but were also shown to be effective as monotherapy. While this
therapy inactivates the trophozoites and
cysts in
Acanthamoeba keratitis in the majority of patients (approximately 90%), there have been notable failures particularly when presentation is late with deep stromal
infection. Additional highly acanthamoebicidal drugs are needed that can penetrate the stroma for synergistic action. This role may be taken up by certain
antineoplastic drugs, such as alkylphosphocholine-1 (
Miltefosine), that also have antiprotozoal activity.