It has been mentioned here that many drugs are created for one condition and used for another. Drugs CAN usually be used for an indication beyond their original market approval, but not advertised as such. This is one way for drug companies to earn more revenue off their existing formulary and it is also sometimes a legitimate next step.
For many years, one such quinine drug, sold as Qualaquin, has been used off label for muscle cramps. The drug is intended for use in acute malaria - only. Though the drug has been effective for the cramps, the adverse events related to its use have concerned the FDA and public health experts for several years. The FDA has warned physicians NOT to prescribe it off label and this July came out with a more serious and concentrated effort to stop this off label prescribing and use. This directive would include any medicine/supplement containing quinine.
The FDA has issued a risk management plan which will include a medicine insert that strongly advises anyone against taking this drug outside of its original intent. From the FDA website :
Additional Information for Patients
Qualaquin is only approved for the treatment of a certain type of malaria (uncomplicated) caused by the parasite Plasmodium falciparum—a rare infection in the United States (approximately 1500 cases per year) primarily resulting from travel abroad.
Qualaquin is not approved for the treatment or prevention of night time leg cramps. Patients using Qualaquin for this condition are at risk for serious side effects.
If you are taking Qualaquin for night time leg cramps, you should discuss other treatment options with your healthcare professional.
If you experience easy bruising, severe nose bleeding, blood in your urine or stool, bleeding gum, or the appearance of unusual purple, brown, or red spots on your skin, contact your healthcare professional immediately.
As you can see above, the drug itself is not a blockbuster by any means. It would do the drug company well if people could take it for other indications, but I must say in this case, they will just have to let it go.