Patients with community-acquired pneumonia (CAP) typically receive empiric antibiotic therapy until a causative microbiologic organism is definitively identified. The most commonly detected organisms are Streptococcus pneumoniae, followed by Legionella, Chlamydia and Mycoplasma agents. However, if no organism is identified, as in most cases, and the clinical response to therapy is good, the course of treatment is completed with the initial antibiotic. Doxycycline has been shown to be highly effective against common respiratory pathogens and is frequently used for outpatient therapy of CAP. Ailani and associates evaluated the effectiveness of intravenous doxycycline as empiric treatment of hospitalized patients who had mild to moderately severe CAP.

Patients with clinical and radiologic diagnosis of CAP before hospital admission were eligible for the study. Patients under 18 years of age, those who were pregnant and those who had other serious medical conditions were excluded from the study. Patients were randomized to receive either intravenous doxycycline in a dosage of 100 mg every 12 hours or a medication regimen chosen by their primary physician. Demographic information, clinical condition and laboratory profiles were similar between groups. In addition, 40 percent of the patients in both groups had documented underlying lung disease. Study parameters included time until resolution of morbidity, length of hospital stay, cost of antibiotics and hospitalization, adverse effects of the medication and the number of antibiotics used per patient.

Of the 87 patients enrolled in the study, 43 were randomized to the doxycycline group and 44 to the control group. While patient age varied widely, few (23 percent) were older than 60 years of age. Patients in the doxycycline group used fewer antibiotics and responded to treatment faster; therefore, they required less time in the hospital. As a result, the median costs of antibiotic therapy and total hospitalization were significantly less than costs for the control group. Adverse effects and the need to change medications also occurred much less frequently in the doxycycline group than in the control group.

The authors conclude that doxycycline is effective in the empiric treatment of hospitalized patients with mild to moderately severe CAP. Besides being effective and relatively inexpensive, doxycycline is associated with fewer adverse effects than other, more complex regimens involving two or more medications.