The first-line therapy for acute Q fever is 14 to 21 days of doxycycline, or fluoroquinolones such as ofloxacin or pefloxacin. Clarithromycin is a potential effective alternative. Chronic Q fever, especially endocarditis, requires treatment for at least 18 months, with the preferred combination of doxycycline and hydroxychloroquine. An alternative treatment for chronic Q fever, when adverse effects of hydroxychloroquine are a problem, is the combination of doxycycline and fluoroquinolones with extended therapy for 3 years or more. Serologic tests may be used to monitor the response to therapy.