Medication Overview

Keflex, also known as cephalexin, is an antibiotic belonging to the class of cephalosporins. It treats a variety of bacterial infections including respiratory tract infections, skin infections, and urinary tract infections. Unlike other antibiotics, Keflex is specifically effective against gram-positive bacteria and some gram-negative bacteria.

Mechanism of Action

Keflex functions by inhibiting bacterial cell wall synthesis. It binds to penicillin-binding proteins inside the bacterial cell wall, interrupting the formation of peptidoglycan, a critical component that provides cell wall strength. This leads to bacterial cell lysis and death, effectively treating the infection.

Indications

Keflex is prescribed for several types of infections. These include upper respiratory tract infections such as strep throat and pneumonia. It is also effective in treating otitis media, skin and soft tissue infections including cellulitis, impetigo, and abscesses. Additionally, it is used for bone infections like osteomyelitis and urinary tract infections.

Dosage Forms

Keflex is available in multiple forms to accommodate different patient needs. These forms include tablets, capsules, and liquid suspensions. The tablets and capsules come in strengths of 250 mg, 500 mg, and 750 mg. The liquid suspension is typically available in a concentration of 125 mg/5 mL or 250 mg/5 mL.

Recommended Dosage

The standard dosage for adult patients varies depending on the infection being treated. For skin infections, the typical dose is 250 mg taken every 6 hours, or 500 mg every 12 hours. For more severe infections, the dose may be increased. Pediatric dosages are generally calculated based on weight, with a common regimen being 25-50 mg/kg/day divided into multiple doses.

Administration Guidelines

Keflex should be taken orally with a full glass of water. To optimize absorption, it can be taken with or without food. For those using the liquid suspension, it is crucial to shake the bottle well before each dose to ensure uniform distribution of the medication. Measuring the dose accurately with a proper measuring device is essential to avoid under or overdosing.

Pharmacokinetics

After oral administration, Keflex is rapidly absorbed from the gastrointestinal tract. Peak plasma concentrations typically occur within one hour. Keflex is widely distributed throughout the body and is excreted largely unchanged in the urine. The elimination half-life of Keflex is approximately one hour, making it necessary for multiple daily dosing to maintain effective drug levels.

Drug Interactions

Several drug interactions should be considered when administering Keflex. It is known to interact with anticoagulants like warfarin, enhancing their effects and potentially increasing the risk of bleeding. Concurrent use with other nephrotoxic drugs may increase the risk of renal damage. Additionally, it may reduce the efficacy of oral contraceptives, necessitating alternative contraceptive measures.

Side Effects

Common side effects include gastrointestinal disturbances such as diarrhea, nausea, and vomiting. Allergic reactions may occur and manifest as rash, pruritus, or urticaria. In some cases, more severe hypersensitivity reactions such as anaphylaxis may develop. Other less common side effects include dizziness, fatigue, and headache.

Precautions and Monitoring

Patients with a known allergy to cephalosporins or penicillins should avoid using Keflex due to potential cross-reactivity. Renal function monitoring is essential for patients with preexisting kidney issues to prevent toxicity. Long-term use may result in overgrowth of non-susceptible organisms, requiring periodic assessment for superinfection.

Storage Instructions

Keflex capsules and tablets should be stored at room temperature, away from moisture and heat. The liquid suspension should be stored in the refrigerator and should not be frozen. Unused portions of the liquid suspension should be discarded after 14 days to maintain efficacy and safety.

Special Populations

In elderly patients, dose adjustments may be necessary based on renal function as it declines with age. Pediatric dosing must be carefully calculated based on body weight to avoid under or overmedicating. Pregnant and lactating women should use Keflex only if clearly needed and after considering potential risks and benefits.

Contraindications

Keflex is contraindicated in patients with a history of hypersensitivity to cephalexin or other cephalosporins. It is also contraindicated in individuals with documented allergic reactions to beta-lactam antibiotics such as penicillins and carbapenems.

Overdose Management

In the event of an overdose, symptomatic and supportive treatment is required. Common symptoms of overdose include nausea, vomiting, diarrhea, and hematuria. It is essential to maintain adequate hydration and renal function monitoring. In severe cases, hemodialysis may be considered to hasten drug elimination.

Patient Counseling Information

Patients should be advised to complete the full course of therapy even if they feel better after a few days, as premature discontinuation may lead to a resurgence of the infection. They should be made aware that Keflex has no effect on viral infections like the common cold or flu. Proper hygiene practices should be followed to prevent the spread of infection.

Clinical Pearls

Keflex is a first-generation cephalosporin, known for its broad-spectrum activity against many gram-positive bacteria and limited gram-negative coverage. It is less likely to cause gastrointestinal discomfort compared to other antibiotics. It serves as a viable alternative in patients with mild penicillin allergies.

Cost and Availability

Keflex is widely available due to its generic status, making it a cost-effective option for many patients. It is listed on various health insurance formularies, and its affordability makes it accessible in different healthcare settings, including outpatient and inpatient facilities.