Wiktionary
metacycline
alt. A tetracycline antibiotic used as a precursor in the industrial synthesis of doxycycline. n. A tetracycline antibiotic used as a precursor in the industrial synthesis of doxycycline.
Wikipedia
Metacycline
Metacycline is a tetracycline antibiotic. It is used as a precursor in the industrial synthesis of doxycycline hyclate. It should not be confused with the antibiotic methicillin (aka meticillin).