Tetracycline combined with which product results in doxycycline capsules?

Doxycycline is a semi-synthetic derivative of tetracycline. The combination mentioned in the question involves the use of Arestin, Periostat, and Atridox, which are products used for oral and periodontal treatments. Among these options, Periostat is specifically indicated for the administration of doxycycline.

Periostat contains low-dose doxycycline and is used primarily for the treatment of periodontal disease due to its antibacterial properties and the ability to promote healing in periodontal tissues. This treatment approach is based on the therapeutic effects of doxycycline on inflammatory responses, making it effective in managing periodontal infections.

The other options, such as Arestin, which contains minocycline, and Atridox, which is a doxycycline gel but is not mentioned in the context of combined capsules, do not involve a direct combination that would result in doxycycline capsules, therefore supporting Periostat as the correct answer in conjunction with tetracycline.