Protozoal diarrhoea — nitazoxanide
Contaminated water is a serious source of infection. Protozoa present in contaminated water, such as Cryptosporidium parvum, Giardia intestinalis and Entamoeba histolytica, can cause persistent diarrhoea. This can lead to more serious complications because of the uncontrolled loss of fluids, nutrients and salts in the faeces. There is currently no approved treatment for diarrhoea resulting from C. parvum infection, and improved therapies for G. intestinalis and E. histolytica are also much needed.
It is estimated that there are over three million deaths from diarrhoea, most of which are children in developing countries. Infectious diarrhoeal diseases, caused by protozoa, bacteria and viruses, are the second highest cause of morbidity and mortality in the world1.
A drug being developed by Florida, US-based Romark Laboratories, nitazoxanide, is claimed to be the first new drug to be investigated for these indications in around 30 years. In a placebo-controlled trial, 189 adults with diarrhoea caused by G. intestinalis or E. histolytica were given one 500mg tablet twice daily for three days. Fourteen had both infections, 22 G. intestinalis and 53 E. histolytica. The patients treated with nitazoxanide saw a significant reduction in the duration of the diarrhoea, and the speed at which the infectious organism was eliminated. Side-effect profiles were similar for both drug and placebo-treated groups.
A related study, undertaken at the University of Rouen, France,2 showed the drug to be effective in combating the diarrhoea caused by a strain of G. intestinalis resistant to existing drug treatments.
A further study, looking at 100 adult and child patients infected with C. parvum, showed the effectiveness of both nitazoxanide tablets and paediatric suspension in infected patients.3 In the placebo-controlled trial on 100 patients, the non-placebo adults were given a single 500mg tablet of the drug, and children a 100mg/5ml strawberry-flavoured oral suspension twice a day for three days. Seven days later, 80% of the treated group were well, compared to 41% of the group receiving placebo.
The drug has been submitted for marketing approval in the US, and should prove a significant advance in the treatment of protozoal diarrhoea.