Philip, a physician from Acarnania, was a friend of, and doctor to Alexander. He is known best for one incident, which is told in slightly differing versions by all the main sources.
In 333 BC Alexander's army passed the Cilician Gates, having spent the winter at Gordium (where Alexander solved the Gordian Knot). As they descended they heard that the local Persian commander was preparing to sack the city of Tarsus; so Alexander led a part of his army at breakneck speed to save the city; and, after they arrived, Alexander decided to bathe in the River Cydnus. When he entered the ice-cold water he was struck down with a severe fever, which most of his companions feared would be fatal (Aristobulus attributed the illness just to fatigue, however, showing once again how difficult it is to establish truth in the sources). Most of the doctors were unable to suggest a cure, but Philip prepared a medicine and declared that, if Alexander followed his instructions, he would get better.
At this time Parmenion sent a letter to Alexander, to warn him that Philip had been bribed by Darius to poison him; Alexander, however, would not believe the information, having complete faith in his physician. He gave the letter to Philip to read, and at the same time drank the medicine that the physician had prepared for him. Philip did not panic, but merely instructed Alexander to follow his course of treatment. The king's speedy recovery fully justified his confidence in the skill, honesty and fidelity of his physician.
All the major sources tell pretty much the same story, with various differences in detail: QC 3.5-6; Pl. Alex. 19; Arr. 2.4; Jus. 11.8; Diod. 17.31. See also Valerius Maximus 3.8.
We know that Philip was still Alexander’s doctor at the siege of Gaza in 332 BC, as Curtius reports that he extracted an arrow from the king’s shoulder (QC 4.6.17-20); but he is not mentioned again, although other doctors are attested as belonging to the court (eg. Critobulus of Cos, who extracted the arrow from Alexander at the Mallian city—Arr. 6.11; and Glaucias, who was executed in 324 BC for failing to save Hephaestion—Arr. 7.14.4).