Is Cephalexin Strong Enough to Clear Infection in Breast Implant?

Keflex is a commonly used antibiotic to prevent infection known as prophylaxis. If your surgeon is concerned about an early infection another course of antibiotic is reasonable as is close surveillance. Personally, I would use a antibiotic that is more effective for the organisms most commonly the cause of implant/wound infections. Spectrum ( range of bacteria the drug effects) is how we choose a drug, it has nothing to do with strength. I may chose a broader spectrum drug such as augmentin, cipro with or without Bactrim. If this is an early infection, it needs to be treated early on or else it can progress to the point where the device may have to be removed. This, however, is extremely rare!

It sounds like your surgeon is being appropriately cautious, and anything that might be going on is a relatively minor problem, or you would be experiencing more remarkable symptoms.
In other words, when implants get infected, because they don't have an immune system or their own blood flow, the infection usually progresses rapidly. This causes rapidly worsening fever, chills, swelling, redness, pain, and often drainage and failure of the incision to heal. It is not subtle.
So, if all you are experiencing is a bit of redness in the skin, but otherwise are doing well (some minor asymmetry in swelling is common early after surgery), I would take the antibiotic prescribed and keep all of your follow up appointments, anticipating a smooth recovery.
If anything seems to be getting worse over time rather than better, call your surgeon immediately for re-evaluation.
Congratulations on your new breast contour!

Your doctor maybe overly cautious. Having an overt infection in the breast after an augmentation is fairly rare. So the Cephalexin or Keflex is likely fine. You will just have to keep an eye on it and if you start having pain, worseing redness, not feeling generally well or fevers then contact your plastic surgeon immediately.

Hope that helps.