Milosevic, who had a history of high blood pressure and related heart problems, was found dead on Saturday in his prison cell while he was on trial at the International Criminal Tribunal for former Yugoslavia (ICTY) in The Hague.
An autopsy found that he died of a heart attack, although further toxicological tests were being carried out.
Dutch toxicologist Donald Uges said he had examined Milosevic’s blood two weeks ago at the request of Dutch doctors who wanted to know why his blood pressure was not dropping despite medication.
Traces of Rifampicin, a powerful antibiotic used to treat leprosy or tuberculosis, were found in his blood, which Dr Uges said countered the effects of his heart medication.
“I am sure he took the medicine himself because he wanted a one-way ticket to Moscow” for treatment, Dr Uges told news agency AFP.
“I don’t think he took his medicines for suicide, only for his trip to Moscow …that is where his friends and family are. I think that was his last possibility to escape The Hague,” Dr Uges said, although he could not prove his claim.
The presence of Rifampicin has yet to be confirmed in the latest report.
The autopsy, conducted by Dutch scientists and attended by Serbian pathologists, pinpointed myocardial infarction, or heart attack, as the immediate cause of death.
However a court spokeswoman said it was too early to rule out suicide, or poisoning, as claimed by Milosevic’s entourage and Milosevic himself in a letter revealed after his death.
In the letter, written a day before his death, Milosevic pleaded with the Russian foreign ministry for protection, charging: “They would like to poison me.”
Adding to controversy, Russia expressed its “distrust” of proceedings and pressed The Hague tribunal to allow its doctors to examine post mortem results.
Belgian newspaper Le Soir reported on Monday that unprescribed medicine was found in Milosevic’s cell in January.
A source at the UN war crimes tribunal told the newspaper that Milosevic’s demand to travel to Russia for medical treatment was denied soon after.
The unidentified source did not tell Le Soir what kind of medicine was found in Milosevic’s cell.
The UN war crimes court will take “all necessary time” to complete an internal inquiry into Milosevic’s death, court spokeswoman Alexandra Milenov said, but did not give any indication of when the results would be public.
Asked for a reaction on the doubts the Russian authorities expressed about the autopsy on Milosevic’s body, Ms Milenov said the Serb pathologists that were present “considered that it was conducted in a professional manner”.
The results of the toxicological report should be known in the course of the week, she added, but refused to comment on the Le Soir report that drugs not prescribed by his Dutch doctors were found in Milosevic’s cell in January.
“The normal procedure is for cells to be regularly checked like in all detention centres, but the results are confidential,” she said.
She added that attorneys or consular representatives are not regularly body-searched when they come to the detention centre.
As the tribunal prepared to release his body, a legal adviser to Milosevic, Zdenko Tomanovic, said his relatives wanted a state funeral in Belgrade.
Mr Tomanovic said Milosevic’s son Marko was seeking a visa so he could pick up his father’s remains, and would arrive from Moscow late on Monday or Tuesday.
Marko said the family might ask for a temporary burial in Moscow if the Serbian authorities failed to guarantee the safety of his mother Mirjana Markovic, who fled Serbia from corruption charges in 2003.
Mr Tomanovic filed a request to Belgrade’s district court for withdrawal of an arrest warrant for her.
The family wants a state funeral for Milosevic, “but not for him to be buried in the Alley of Great Men,” Mr Tomanovic said, referring to the resting place of national luminaries in a central Belgrade cemetery.
Serbian President Boris Tadic on Sunday ruled out a state funeral, saying such a ceremony would be “completely inappropriate” given Milosevic’s role in the Balkans wars that claimed at least 200,000 lives.
Markovic told a Serbian newspaper she had yet to decide where her husband should be buried but preferred Pozarevac, their hometown near Belgrade.
Their daughter Marija said she wanted the body returned home to Montenegro, where the family originated and which is federated with Serbia.
The man branded the “Butcher of the Balkans” had been on trial for four years charged with 66 counts of genocide, crimes against humanity and war crimes involving conflicts in Bosnia, Croatia and Kosovo that tore Yugoslavia apart in the 1990s.
The tribunal said it would hold a hearing on Tuesday at 0800 GMT that was expected to formally close the Milosevic trial.