How Long Does Keflex Stay in Your System?

Keflex (Cephalexin) Prescription Facts

For patients allergic to penicillin, there is a 10% chance they will also have an allergic reaction to Keflex. The general population has only a 0.1% chance of being allergic to the drug. Potential signs of an allergic reaction include itching, trouble breathing, rash, and blistered or peeling skin.

Individuals with compromised renal function may only be able to tolerate reduced doses of cephalexin. Clinical observation is sometimes necessary in such cases to avoid the development of serious complications.

Cephalexin is approved for use in pregnant and lactating mothers. No harmful side effects have yet been linked to cephalexin treatment; however, Keflex is present in the milk of lactating mothers. It’s important to recognize that a lack of evidence doesn’t guarantee an infant will be unaffected by drug exposure, and caution should always be exercised when treating pregnant or lactating patients. Children and the elderly are generally able to tolerate cephalexin without issues, except for those with a history of renal failure.

Keflex (Cephalexin) Regulations

Cephalexin should not be mixed with the diabetic medication metformin due to the risk of serious health complications. Keflex can interfere with the body’s utilization of metformin and result in elevated levels of the drug. Alcohol is also to be avoided while taking Keflex, as alcohol consumption can interfere with Keflex absorption. Talk to your doctor if you have a history of intestinal inflammation such as colitis as this can increase the likelihood of having a hypersensitive reaction to Keflex treatment.

Keflex is safe for most people who have mild to moderate allergies to penicillin but it is not recommended for individuals with severe penicillin allergies.

Most Commonly Abused Drugs Containing Keflex (Cephalexin)

Cephalexin is considered non-addictive by the Federal Drug Administration (FDA). Treatment with cephalexin does not trigger a pleasurable response or activate reward pathways in the brains. Its sole function is to compromise the function of certain bacterial cells and restore bacterial balance to the body.

Keflex does not trigger withdrawal symptoms when treatment is stopped but it can cause side effects in certain individuals. Potential side effects of Keflex use may include gastrointestinal distress in patients who are hypersensitive to the drug. Diarrhea, nausea, and vomiting are the most common side effects. Hypersensitive reactions may also be expressed in skin rashes, fever, and urticaria.

How Keflex (Cephalexin) Affects the Brain and Body

Keflex destroys bacteria by preventing the bacterial cells from synthesizing cell walls. Cephalexin is one of the most commonly prescribed medications worldwide and is on the World Health Organization’s List of Essential Medicines. Keflex does not treat infections caused by Enterococcus, Pseudomonas, or methicillin-resistant Staphylococcus aureus (MRSA). Cephalexin cannot treat viral infections such as those responsible for the common cold, the flu, or acute bronchitis.

Half-Life of Keflex (Cephalexin)

Keflex has a half-life of eight hours before being excreted in the urine. The typical dose of Keflex is 250 mg every six hours, with treatment lasting from 7 to 14 days. In healthy patients with more widespread infection, doses may be increased to 500 mg every 12 hours. For severe infections, doses may be increased to up to four grams a day split between two to four doses.

Factors That Influence How Long Keflex (Cephalexin) Stays in Your System

Cephalexin absorption and half-life are not affected by food intake. Cephalexin is acid stable and therefore can be taken without regard to meals. Peak plasma concentrations of Keflex are reached approximately one hour following ingestion. Blood serum levels of cephalexin are detectable six hours following administration of the drug.

How Long Does Keflex (Cephalexin) Stay in Your Urine, Hair, and Blood?

Keflex is almost entirely excreted in the urine. Studies show that more than 90% of the drug passes through the urine within eight hours of a single, isolated dose of Keflex. Peak urine concentrations following a 250-mg dose were 1,000 mcg/mL. When a full antibiotic round of cephalexin is completed, it can take up to 72 hours for the patient to eliminate the drug.

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