Children with HIV/Aids are missing out on treatment because of a shortage of specially designed drugs, doctors have said.
Adult drugs are difficult for children to swallow
Although more than two million children have HIV, few live in wealthier countries.
Médecins Sans Frontières (MSF) warns the resulting lack of a profitable market means custom-made drugs for children are in short supply.
Doctors spoke out at the International Aids Conference in Bangkok.
Syrups are foul-tasting and pills are too big for children to swallow, said Dr David Wilson, medical coordinator of MSF programs in Thailand.
Doctors have to spend extra time working out the correct doses to give to children because the formulations are designed for adult-sized people, he said.
"Commercial pharmaceutical do not bother to develop paediatric formulations of Aids medicines because children are not an attractive market," he said.
Formulations designed specifically for children are more costly than adult versions.
The best price for one form of HIV treatment designed for children is about $1,300. The equivalent treatment for adults costs only $200 per patient, he said.
Drugs are not the only problem. Standard tests to check for HIV infection are not reliable in infants younger than 18 months, doctors heard.
Monitoring drug treatment is also difficult because most of the commercially available machines that check CD4 levels - which reflects a drug's success in controlling the disease - are not adapted for use on young children, said Dr Wilson.
Fernando Pascual, MSF pharmacist, said: "Unless there is increased pressure on drug makers and intervention from governments, it will be years before new therapies are available."
Nearly 90% of children diagnosed with HIV live in sub-Saharan Africa and about half of them die before the age of two.
A spokesman from National Aids Map said: "One of the key differences between the HIV epidemics in rich and poor countries is the extent to which children are involved.
"There are relatively few HIV-positive children in the UK and other rich countries, but in poorer countries children are often bearing the brunt of the epidemic.
But he said a lack of appropriate drugs for children was a global problem.
"Even in rich countries, there are fewer drugs available for the treatment of HIV in children. Even when they are available they can be difficult to take, meaning that it is even harder to achieve the very high levels of medicine taking needed for anti-HIV drugs to work well."