In the article on Apollo command module design, I read:
The cabin atmosphere at launch was changed to 60% oxygen and 40% nitrogen at sea-level pressure: 14.7 psi (10.1 N/cm2). During ascent the cabin rapidly vented down to 5 psi (3.4 N/cm2), releasing approximately 2/3 of the gas originally present at launch. The vent then closed and the environmental control system maintained a nominal cabin pressure of 5 psi (3.4 N/cm2) as the spacecraft continued into vacuum. The cabin was then very slowly purged (vented to space and simultaneously replaced with 100% oxygen), so the nitrogen concentration fell asymptotically to zero over the next day. Although the new cabin launch atmosphere was significantly safer than 100% oxygen, it still contained almost three times the amount of oxygen present in ordinary sea level air (20.9% oxygen). This was necessary to ensure a sufficient partial pressure of oxygen when the astronauts removed their helmets after reaching orbit. (60% of 5 psi is 3 psi, compared to 20.9% of 14.7 psi (10.1 N/cm2), or 3.07 psi (2.12 N/cm2) in sea-level air.)
The environment within the astronauts' pressure suits was not changed. Because of the rapid drop in cabin (and suit) pressures during ascent, decompression sickness was likely unless the nitrogen had been purged from the astronauts' tissues prior to launch. They would still breathe pure oxygen, starting several hours before launch, until they removed their helmets on orbit. Avoiding the "bends" was considered worth the residual risk of an oxygen-accelerated fire within a suit.
The article on Oxygen Toxicity has a following table:
"Several hours" seem like much longer than the 96 minutes the most persistent test subject withstood, of exposure to pure oxygen at atmospheric pressure, and risk of oxygen-accelerated fire within a suit seems like the least of worries the astronauts would have.
How were they dealing with oxygen toxicity before and during the launch, before the pressure was vented to 5 psi?