Ramatu Musa has little doubt why her eldest son is deaf. He is, she alleges, a victim of an illegal drug trial in Nigeria by Pfizer, the world’s largest drug company.

“I am so bitter because he is my eldest. All my hopes were on him. I expected him to care for me when I am older,” Mrs Musa, 47, told The Times. “We are poor. I have no money to look after him. They [Pfizer] did this to him.”

Nigerian lawyers maintain that Smai’la, 17, was one of about 200 children used as guinea-pigs by Pfizer during one of the worst meningitis epidemics to hit the country, in 1996. By the time that it had run its course, more than 10,000 people, many of them children, had died.

Last month the Kano state government and the Nigerian federal Government filed lawsuits against Pfizer seeking nearly $10 billion (£5 billion) in damages. They allege that an untested drug, Trovan Floxacin, which at the time was not licensed anywhere else in the world, was administered.

The company denies the allegations. “Trovan unquestionably saved lives and Pfizer strongly disagrees with any suggestion that the company conducted its study in an inappropriate and unethical manner,” it said.

Trovan was approved for use in the United States in 1997 – but for adults, not children. It was withdrawn two years later because several patients died of liver problems. “It is not in use anywhere today,” a company spokesperson said.

According to papers submitted by the authorities, the drug trial resulted in deaths, brain damage, paralysis and slurred speech – all neurological side-effects of the type of virulent meningococcal disease that then devastated the region.

One US court has dismissed a lawsuit brought by disabled Nigerians, but the case may be reheard on appeal. Either way, the new cases would be binding outside Nigeria because of international conventions.

“A successful prosecution would affect Pfizer’s operations well beyond Nigeria’s borders,” said a senior company lawyer in Lagos who acts for other big international companies operating in Nigeria. “I think they will have to settle out of court.”

The accusations against Pfizer surfaced seven years ago, when doctors involved in the trials questioned the ethics involved in using poor countries as testing grounds for unapproved drugs after an in-depth inquiry by The Washington Post newspaper. One physician suggested that Nigerian documents had been falsified; another said that follow-up monitoring tests on the children were inadequate.

A doctor involved in the trials even brought a lawsuit against the company, but it was dropped and since then neither he nor the company has made any further comment.

Smai’la, one of five children, sat next to his mother on a wooden bench inside a modest house on the outskirts of the sprawling northern Nigerian city of Kano – home to two million mostly impoverished people.

Oblivious of the events around him, he leant his head against the bare brick wall and cast suspicious glances at yet more foreign visitors.

He lost his hearing after taking part in the trial at the local hospital when he was six years old. Now he earns his living grinding grain for fellow villagers with a machine donated by a local wellwisher, but he has run away from home on occasion, angry that his mother cannot afford to send him to a school for deaf children.

His mother, like the parents of many of the other children in the trial, tells a story that raises many concerns over Pfizer’s behaviour. Contrary to the company’s assertion, she says that she was never told of any drug trial. She says she just took a desperately sick child to hospital. Local nurses or doctors said nothing to her.

The same story is told by others in Kano. A father, whose son was also in the drug trial, blames Pfizer for the recurring bouts of illness that have plagued the 14-year-old boy ever since. He calls the company “vampires who preyed on poor Africans” and says that he wants compensation.

The company says that it is not possible to know if those who succumbed would have died in any case, or if the death rates would have been much higher if the drug had not been used.

Of the 200 alleged guinea-pigs, 11 died. Not all were given Trovan, which was administered orally, as opposed to injections of the approved and most commonly used antibiotic, ceftriaxone.

Sources at the medical charity Médecins sans Frontières (MSF), which also had a clinic at the rundown Kano hospital, told The Times that Pfizer doctors wanted to compare the two drugs. For this reason, they say that children who did not respond to the treatment were kept on the drugs for sake of the trial.

“In normal circumstances, the first thing you do when a patient does not respond to a drug when dealing with a killer like meningitis is to change the drug. They did not do this, they kept them on it,” an authoritative MSF source said.

He also believes that different amounts of the alternative drug were administered than would have normally been the case. “Some of the things that went on do not seem to have been appropriate,” the source said.

Fauda Hassan, a father of another guinea-pig, says that he believes that the truth will never come out, partly because of the complicity of corrupt local officials and the financial power of one of the world’s leading international companies. He may be right.

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