Racquet manufacturer Head has questioned the decision to ban the use of meldonium, as they continue to stand by Maria Sharapova.
Sharapova tested positive for the drug which the World Anti-Doping Agency (Wada) added to their list of banned substances on 1 January.
Head wants Wada to scientifically prove why the drug should be banned.
The company believes the drug should not be prohibited but instead come with a dosage limit.
Russia's Sharapova tested positive at the Australian Open in January.
The five-time Grand Slam champion will be suspended from 12 March and could face a four-year ban.