On Wednesday, a US Senate panel launched a bipartisan probe into pharmaceutical pricing in quest of documents from four drugmakers, including Valeant Pharmaceuticals and Turing Pharmaceuticals, the companies that were a part of a controversy over price hikes of lifesaving drugs.

As per a statement from the panel's Republican Chairwoman Susan Collins and Claire McCaskill, its top Democrat, the Senate's Special Committee on Aging has also asked for information from Retrophin Inc and Rodelis Therapeutics.

Furthermore, on Wednesday, a US House of Representatives investigative committee's Democratic members asked Republicans for calling a vote to subpoena Valeant and Turing.

In September, these Democratic leaders asked for an investigation of drug prices, emboldened by press reports regarding an over 5,000% overnight hike of a toxoplasmosis drug made by Turing and an over 600% hike in a blood pressure treatment from Valeant.

That investigation and the news that according to Democratic Presidential candidate Hillary Clinton the increases were 'outrageous' and the release of her plan to limit drugmaker profits, has badly affected their stock prices. As per drugmakers and their defenders, the prices of drugs were hiked to aid discovery and development of pioneering new treatments.

Republicans haven't taken up the effort broadly so far. Investors and analysts have asserted that they would take a wider bipartisan push for possibly changing how drugmakers decides the price of their medicines.

House investigative committee Republican Chairman Jason Chaffetz could authorize an investigation, and has blocked it so far.