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Keflex (cephalexin) is a cephalosporin antibiotic somewhat similar to penicillin. Like all antibiotics it only works on certain types of bacteria; infections should be identified before starting treatment to determine which antibiotic will be most beneficial.

The medication may be utilized to treat streptococcal and certain other types of infections in nearly every part of the body, including bones and joints, kidneys and bladder, the respiratory tract, tonsils, ears, and various skin infections.

Keflex is a preferred treatment in some conditions, particularly infections involving the skin. It is also commonly used in conditions in which penicillin would be the preferred antibiotic, but use is inadvisable; usually because a patient is hypersensitive (allergic) to penicillin. Only about 10 percent of individuals who are allergic to penicillin have a reaction to cephalexin. Note, however, that those 10 percent tend to be those who have severe reactions to penicillin; it should be used with caution in such cases.

Treatment Overview

Keflex comes in capsules, which should be swallowed whole and not split, opened, dissolved in food or drink, or otherwise mangled. Food is optional; taking the medication after a meal may ease side effects of nausea. Keflex should be taken with a full glass of fluid, and some effort should be made to stay hydrated throughout treatment. Results are best if doses are spread evenly apart and taken at the same times each day, to maintain consistent levels of the drug in the body.

In otherwise healthy adults treatment is usually straightforward:

• For most infections, 250 mg is taken every 6 hours for 5 to 14 days, with the average duration of treatment being 10 days.
• For treating strep throat, bladder infections and skin infections, the typical dose is 500 mg every 12 hours for 10 to 14 days.
• In severe cases, dosage may be increased to twice the standard amount.
• In very high doses administration through some other route, such as IV, may be preferred to prevent liver damage.

When treatment is working well, most patients begin to feel better after the first day or two of treatment, and often feel completely fine before treatment ends. It is important to finish treatment regardless, to prevent a resurgence of the infection and to avoid contributing to resistant bacteria.

If at any point during treatment the infection appears to be worsening, a doctor should be consulted. Likewise if the infection persists at the end of treatment; it is likely additional measures will need to be taken.

Precautions & Side Effects

Individuals who have a history of kidney, liver or bowel disease are more likely to experience potentially serious side effects. That is not to say Keflex must not be used; but patients should understand risks and know what warning symptoms to be alert for. Speak with a doctor before use.

Keflex is known to interact with certain other medications:

• Metformin
• Probenecid
• Blood thinners

Using Keflex with the above medications can significantly impact the effectiveness of one or more of the drugs, which can lead to potentially dangerous complications.

The medication is unlikely to harm unborn or nursing babies, but parents should discuss possible risks with a trusted doctor before starting treatment.

Side effects are typically mild and similar to those encountered with any antibiotic:

• Nausea
• Vomiting
• Headache
• Dizziness
• Diarrhea

The above side effects are not cause for concern unless severe. Note that even mild diarrhea can be quite dehydrating; be sure to drink extra fluids if diarrhea occurs.

Rarely more serious adverse effects may happen. Warning symptoms which call for medical attention include:

• Swollen or painful joints
• Yellowing of the skin or eyes
• Confusion or hallucinations
• Unusual bleeding or bruising
• Unexplained rash or itching

With the exception of severe allergic reactions, it is extremely unlikely that Keflex will produce life-threatening adverse effects if used properly.