The drug at the centereof Maria Sharapova's doping case, regularly given to Soviet troops in the 1980s to boost their stamina while fighting in Afghanistan, is normally prescribed for medical use for periods of four to six weeks.
Sharapova faces possible sanctions after testing positive for meldonium, a drug the Russian tennis star said she had been using for 10 years for various medical issues.
The Latvian company that manufactures meldonium said the normal course of treatment is much shorter.
"Depending on the patient's health condition, treatment course of meldonium preparations may vary from four to six weeks," Grindeks said in an emailed statement Tuesday to The Associated Press. "Treatment course can be repeated twice or thrice a year. Only physicians can follow and evaluate patient's health condition and state whether the patient should use meldonium for a longer period of time."
Sharapova, a five-time Grand Slam champion, said Monday she failed a doping test at the Australian Open in January for meldonium, which became a banned substance under the World Anti-Doping Agency code this year.
Meldonium is a heart medicine which improves blood flow and is little-known in the U.S., but it was once common in the Soviet military.
The drug's inventor, Ivars Kalvins, told Latvian newspaper Diena in a 2009 interview that meldonium was given to soldiers during the 1980s, when Soviet forces were fighting in Afghanistan.
"High altitudes. Oxygen deprivation. If they have to run 20 kilometers with all the gear, at the end they would get ischemia [a blood circulation condition]," Kalvins was quoted as saying.
"They were all given meldonium. They themselves were not aware they were using it. No one was being asked [if they agree to it] back then."
Kalvins said meldonium was "not doping," adding that it "allows you to withstand more physical pressure, but the body still spends its spare reserves."
Sharapova said Monday she had taken meldonium for a decade following various health problems including regular sicknesses, early signs of diabetes and "irregular" results from echocardiography exams.
"I was first given the substance back in 2006. I had several health issues going on at the time," she said. Sharapova didn't specify whether she had used it constantly since then.
Meldonium was banned because it aids oxygen uptake and endurance, and several athletes in various international sports have already been caught using it since it was banned on Jan. 1.
The wave of meldonium cases has echoes of a doping scandal involving another Soviet military drug, bromantan, which was banned after being found in Russian athletes' samples at the 1996 Atlanta Olympics.
While Grindeks has previously stated that meldonium can provide an "improvement of work capacity of healthy people at physical and mental overloads and during rehabilitation period," the Latvian company said Tuesday that it believed the substance would not enhance athletes' performance in competition and might even do the opposite.
"It would be reasonable to recommend them to use meldonium as a cell protector to avoid heart failure or muscle damage in case of unwanted overload," the company said.
Drug designed for chronic heart, circulation conditions
Grindeks said that, in sports activity, the drug slows down how the body breaks down fatty acids to produce energy.
Grindeks did not comment when asked whether someone with the symptoms Sharapova described would be a suitable patient for meldonium. The company said it was designed for patients with chronic heart and circulation conditions, those recovering from illness or injury and people suffering with "reduced working capacity, physical and psycho-emotional overload."
Meldonium is not approved by the U.S. Food and Drug Administration.
While meldonium was put on banned list as of Jan. 1, the decision to ban it had been announced by WADA and sports organizations as early as September 2015. Sharapova said she received an email with information on the changes in December, but did not read the information at the time.
The AP was able to buy vials and tablets of meldonium over the counter in Moscow on Tuesday. Accompanying documentation stated that side effects could include blood pressure changes, irregular heartbeat and skin conditions.
German anti-doping expert Mario Thevis, who helped to develop the test for meldonium, told the AP that testing was reliable despite meldonium's recent addition to the WADA banned list.
"There is a potential of the substance to enhance performance and it has been described as a means to facilitate recovery and to enhance physical as well as mental workload capabilities," Thevis, a professor at the anti-doping laboratory in Cologne, Germany, said in a telephone interview. "It can be tested as reliably as any other doping agent."