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Pharmacoepidemiol Drug Saf. 2014 Sep;23(9):911-7. doi: 10.1002/pds.3644. Epub 2014 May 28.

Use of an active surveillance system by the FDA to observe patterns of quinine sulfate use and adverse hematologic outcomes in CMS Medicare data.

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Office of Surveillance and Epidemiology, Center for Drug Evaluation and Research, Food and Drug Administration, Silver Spring, MD, USA.



In 2005, the Food and Drug Administration approved Qualaquin (quinine) for treatment of malaria and later ordered unapproved quinine formulations off the market. In 2009, labeling for Qualaquin added a warning for use for leg cramps, as serious hematologic reactions could occur. We examined quinine use trends among Medicare beneficiaries focusing on indications for use and associations with adverse hematologic outcomes.


Medicare beneficiaries, aged 65 years and older, in 2006-2012, were included in incident quinine or comparator, diltiazem, cohorts if 183 days prior to dispensing, they were enrolled in Medicare, had no dispensing of quinine, diltiazem, ticlodipine, clopidogrel, and sulfonamide drugs, and had no diagnoses of thrombocytopenia, immune thrombocytopenic purpura (ITP), thrombotic microangiopathy (TMA), or hemolytic-uremic syndrome (HUS). Diagnoses of malaria or leg cramps were observed during 183 days prior to index dispensing. Outcomes of ITP, TMA, or HUS in inpatient or emergency room settings were then observed during drug use.


Prevalent use of quinine decreased by 99%, from 419 675 to 6036 users during 2006-2012. Of 88 066 quinine users, 9 had diagnoses of malaria and 36 218 had leg cramps. Incidence rates (per 1000 person-years) for ITP were quinine 1.67 and diltiazem 0.40 [incidence rate ratio 4.2 (95% confidence interval 2.5, 6.5)], for TMA were quinine 0.23 and diltiazem 0.03 [incidence rate ratio 6.9 (95% confidence interval 1.3, 24.0)], and for HUS were quinine 0 and diltiazem 0.01.


Use of quinine decreased substantially, although diagnoses of leg cramps persist. To our knowledge, this is the first demonstration of an association for quinine and ITP and TMA in claims data.


active surveillance; hematologic; pharmacoepidemiology; quinine

[Indexed for MEDLINE]

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