The extent of Galen's written work was so great that Galen himself felt the need to provide a bibliography organizing and explaining his own writings. This work, which Galen compiled in 190 CE, has been called the first auto-bibliography. Some of Galen's work survived through Arabic and Syriac translations rather than the original Greek. According to Theodore Besterman, The Beginnings of Systematic Bibliography, 2nd ed (1936) p. 3, an early bibliography of Galen's writings in Arabic was compiled in the ninth century by the physician and translator into Arabic and Syriac Hunain ibn Ishāq (Abu Zayd Hunayn ibn Ishāq al-Ibadi). In February 2015 the Al-Islam.org website stated that Hunain, who was known as Johannitius Onan to Latin readers, "translated 95 works of Galen from Greek to Syriac and 99 into Arabic." Hunain's bibliography of Galen's writings survived in two manuscripts, both of which were preserved in Istanbul when Besterman published; it was first published in print in German translation in 1925 and 1932.
Considering the central importance of Galen's writings in medicine from the time he wrote well through the sixteenth and the seventeenth century, and the need for physicians to make sense of such a large number of his texts, it does not seem surprising that the first printed bibliography of any medical author would be De divisione librorum Galeni by the fourteenth century Italian physician Gentile da Foligno (Gentilis Fulginas) who appears to have been the first European physician to perform a dissection on a human (1341). Gentile's very brief listing was first published in the collective volume, containing over ten short texts, entitled Articella su Opus artis medicinae edited by Franciscus Argilagnes of Valencia, and published in Venice by Hermannus Liechtenstein on March 29, 1483. Among the other works published in that volume was the first printing (in Latin) of the Hippocratic Oath.
In February 2015 a digital facsimile of 1483 Articella was available from the Bayerische StaatsBibliothek at this link. ISTC No. ia01143000.
My thanks to Eugene Flamm for pointing out that the Articella of 1483 contains the first bibliography of a medical author and the first printing of the Hippocratic Oath.