to the editor: King and Pippin¹ hesitate to make doxycycline (Vibramycin) their first choice for outpatient treatment of community-acquired pneumonia in spite of their praise for its low cost and easy dosing schedule. Their only stated reason for reservation is that Streptococcus pneumoniae “resistance to this agent is increasing.”

The authors' two references on this point offer no evidence for their assertion. One is a primary research paper which does not mention doxycycline.² The other is a review article by Mandell³ which contains a statement similar to the one made by Drs. King and Pippin. The reference given for this claim in the Mandell article is a 1973 paper by Gopalakrishna and Lerner.⁴ These authors serially tested for tetracycline resistance in one hospital over the course of 31 months; they did not report similar testing for doxycycline. The data presented do not allow the reader to determine the prevalence of doxycycline resistance at any point in time, let alone ascertain that the rate of resistance had increased during the study.

Perhaps Drs. King and Pippin have made the common error of assuming that tetracycline resistance, which is indeed common for S. pneumoniae, implies doxycycline resistance as well. This is not true.⁵

Doxycycline is consistently active against all common typical and atypical bacterial causes of pneumonia, is inexpensive, offers twice-daily dosing, has a favorable side-effect profile, and achieves unusually high penetration into lung tissue and especially into alveolar macrophages.^5,6 Doxycycline is, in short, a nearly ideal antibiotic for initial outpatient treatment of community-acquired pneumonia in adults.

in reply: We wish to apologize to the readers of American Family Physician for incorrectly referencing our comments concerning doxycycline resistance. We intended to reference items 13 and 19 rather than items 13 and 16.

Dr. Woolley wonders why we hesitate to make doxycycline our first choice for out-patient treatment of community-acquired pneumonia. The article we intended to cite¹ indicates that doxycycline resistance is a class effect, since both doxycycline and tetracycline resistance are plasmid-mediated. The article referenced by Dr. Woolley² is a letter to the editor pointing out in vitro data which demonstrate 21 percent intermediate and full resistance to tetracycline (for S. pneumoniae) and 16 percent intermediate and full resistance to doxycycline. In vivo clinical experience with doxycycline in pneumonia is very limited. In contrast, the American Thoracic Society guidelines show erythromycin (Ery-Tab) to be a very cost-effective choice.³ In addition, erythromycin has more reliable activity against Legionella pneumophila than doxycycline. Further clinical in vivo research with doxycycline may uphold Dr. Woolley's position; until then, we feel that erythromycin is still the first choice for initial antibiotic therapy of uncomplicated community-acquired pneumonia.