"Some of them have skin problems and lung problems, respiratory problems which we can more-or-less control, but every day the virus is increasing in number and it's only a matter of time until it overcomes them," he added.
Buying cheaper drugs, he says, will enable him to treat an additional 20 children every month - but the move will bring him into direct conflict with the Kenyan government, and international drugs companies.
The Indian group makes cheap 'generic' copies of drugs that are patent-protected elsewhere in the world. The United States says this is illegal and has complained to the World Trade Organisation.
Father d'Agostino said the children in his care could wait no longer and that the continuing high prices of official drugs reflected the "darker side of capitalism".
Africa 'held to ransom'
He accused the big pharmaceutical companies of holding Africa to ransom and described the children in his care as "on the brink."
"Some of them have skin problems and lung problems, respiratory problems which we can more-or-less control, but every day the virus is increasing in number and it's only a matter of time until it overcomes them," he added.
Bringing generic drugs into the country may not be a problem for Father d'Agostino if they had been donated.
But buying them breaks Kenya's current laws, and could invoke the ire of the international drug companies.
Price anger
His move comes amid demands from non-governmental organisations (NGOs) in Kenya for the companies to honour a commitment made last year to reduce their prices.
The NGOs say an offer by drug companies last year to reduce prices by up to 85% has not been followed through, and what price reductions there have been are being offered piecemeal to individual doctors.
On Wednesday, drug firm Glaxo Smith Kline, announced that it would offer HIV drugs at up to 90% discount to non-profit organisations, as long as these organisations take on the task of delivering the medicine to the patients.
But a spokeswoman for the medical group Medecins Sans Frontieres in Nairobi said this was not enough.
She said most NGOs were not in a position to medically supervise the distribution of the drugs and an across-the-board slashing of prices was urgently needed.