Keflex 750mg Capsules
It is used to treat bacterial infections.
Drug Class
Antibiotic
Pharmacologic Class
First-generation cephalosporin
Pregnancy Category
Category B
FDA Approved
Jan 1971
DEA Schedule
Not Controlled
Overview
What is this medicine?
Cephalexin is an antibiotic medication used to treat a wide variety of bacterial infections, such as infections of the skin, ears, throat, bones, and urinary tract. It works by stopping the growth of bacteria.
How to Use This Medicine
Taking Your Medication
To use this medication correctly, follow your doctor's instructions and read all the information provided. Take your medication as directed, with or without food. If you experience stomach upset, taking it with food may help. Continue using the medication even if your symptoms improve.
Storing and Disposing of Your Medication
Store your medication at room temperature in a dry place, avoiding the bathroom. Keep all medications in a safe location, out of the reach of children and pets. Dispose of unused or expired medications properly. Do not flush them down the toilet or pour them down the drain unless instructed to do so. If you have questions about disposal, consult your pharmacist. You may also have access to drug take-back programs in your area.
Missing a Dose
If you miss a dose, take it as soon as you remember. However, if it's close to the time for your next dose, skip the missed dose and resume your regular schedule. Do not take two doses at the same time or take extra doses to make up for the missed one.
To use this medication correctly, follow your doctor's instructions and read all the information provided. Take your medication as directed, with or without food. If you experience stomach upset, taking it with food may help. Continue using the medication even if your symptoms improve.
Storing and Disposing of Your Medication
Store your medication at room temperature in a dry place, avoiding the bathroom. Keep all medications in a safe location, out of the reach of children and pets. Dispose of unused or expired medications properly. Do not flush them down the toilet or pour them down the drain unless instructed to do so. If you have questions about disposal, consult your pharmacist. You may also have access to drug take-back programs in your area.
Missing a Dose
If you miss a dose, take it as soon as you remember. However, if it's close to the time for your next dose, skip the missed dose and resume your regular schedule. Do not take two doses at the same time or take extra doses to make up for the missed one.
Lifestyle & Tips
- Take the medication exactly as prescribed by your doctor, even if you start to feel better. Do not skip doses or stop taking it early, as this can lead to antibiotic resistance and a return of the infection.
- Cephalexin can be taken with or without food. If it causes stomach upset, try taking it with food or milk.
- Drink plenty of fluids while taking this medication.
- Avoid alcohol consumption, as it may worsen side effects like stomach upset.
- Do not share this medication with others, even if they have similar symptoms.
Available Forms & Alternatives
Available Strengths:
Generic Alternatives:
Dosing & Administration
Adult Dosing
Standard Dose:
250 mg to 1 g every 6 or 12 hours, depending on infection severity and type. For 750mg capsules, typically 750mg every 12 hours for specific indications.
Dose Range:
250 - 1000 mg
Condition-Specific Dosing:
mildToModerateInfections:
250 mg every 6 hours or 500 mg every 12 hours
severeInfections:
500 mg every 6 hours or 1 g every 12 hours
skinAndSoftTissueInfections:
500 mg every 12 hours
streptococcalPharyngitis:
250 mg every 6 hours or 500 mg every 12 hours for at least 10 days
urinaryTractInfections:
250 mg every 6 hours or 500 mg every 12 hours
Pediatric Dosing
Neonatal:
Not established (use with caution, consult specific guidelines)
Infant:
25-50 mg/kg/day in divided doses every 6 or 8 hours
Child:
25-50 mg/kg/day in divided doses every 6 or 8 hours; up to 100 mg/kg/day for severe infections (max 4 g/day)
Adolescent:
Adult dosing may apply based on weight and maturity
Dose Adjustments
Renal Impairment:
Mild:
CrCl 30-59 mL/min: No dose adjustment typically needed, but consider increasing dosing interval for higher doses.
Moderate:
CrCl 15-29 mL/min: 250-500 mg every 8-12 hours.
Severe:
CrCl <15 mL/min: 250-500 mg every 12-24 hours.
Dialysis:
Hemodialysis: 250-500 mg after each dialysis session. Peritoneal Dialysis: 250 mg every 12 hours.
Hepatic Impairment:
Mild:
No adjustment
Moderate:
No adjustment
Severe:
No adjustment
Pharmacology
Mechanism of Action
Cephalexin is a bactericidal antibiotic that inhibits bacterial cell wall synthesis by binding to one or more of the penicillin-binding proteins (PBPs). This binding interferes with the final transpeptidation step of peptidoglycan synthesis in the bacterial cell wall, leading to inhibition of cell wall assembly and eventual bacterial cell lysis.
Pharmacokinetics
Absorption:
Bioavailability:
>90%
Tmax:
Approximately 1 hour (fasted state)
FoodEffect:
Food may delay the rate of absorption (Tmax) but does not significantly affect the extent of absorption (AUC).
Distribution:
Vd:
Approximately 0.26 L/kg
ProteinBinding:
10-15%
CnssPenetration:
Limited (does not achieve therapeutic concentrations in CSF)
Elimination:
HalfLife:
0.5-1.2 hours (normal renal function)
Clearance:
Approximately 210 mL/min (renal clearance)
ExcretionRoute:
Renal (glomerular filtration and tubular secretion)
Unchanged:
80-90%
Pharmacodynamics
OnsetOfAction:
Rapid (within 1 hour)
PeakEffect:
Approximately 1 hour (corresponds to Tmax)
DurationOfAction:
Dependent on dosing interval (typically 6-12 hours based on half-life and MIC)
Safety & Warnings
Side Effects
Urgent Side Effects: Seek Medical Help Right Away
While rare, some people may experience severe and potentially life-threatening side effects when taking this medication. If you notice any of the following symptoms, contact your doctor or seek medical attention immediately:
Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin (with or without fever)
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Signs of a severe skin reaction (Stevens-Johnson syndrome/toxic epidermal necrolysis), such as:
+ Red, swollen, blistered, or peeling skin (with or without fever)
+ Red or irritated eyes
+ Sores in the mouth, throat, nose, or eyes
Signs of liver problems, including:
+ Dark urine
+ Tiredness
+ Decreased appetite
+ Upset stomach or stomach pain
+ Light-colored stools
+ Vomiting
+ Yellow skin or eyes
Fever, chills, or sore throat
Unexplained bruising or bleeding
Feeling extremely tired or weak
Confusion
Hallucinations (seeing or hearing things that are not there)
Difficulty urinating or changes in urine output
Seizures
Severe dizziness
Severe headache
Severe joint pain
Vaginal itching or discharge
Important Note: Diarrhea is a common side effect of antibiotics. However, in rare cases, a severe form of diarrhea called C. diff-associated diarrhea (CDAD) may occur. This can lead to a life-threatening bowel problem. If you experience stomach pain, cramps, or very loose, watery, or bloody stools, contact your doctor immediately. Before treating diarrhea, consult with your doctor.
Other Possible Side Effects
Most people do not experience severe side effects, and some may not have any side effects at all. However, if you notice any of the following side effects or any other unusual symptoms, contact your doctor or seek medical attention:
Stomach pain or diarrhea
Upset stomach or vomiting
Reporting Side Effects
This is not an exhaustive list of possible side effects. If you have questions or concerns about side effects, contact your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
While rare, some people may experience severe and potentially life-threatening side effects when taking this medication. If you notice any of the following symptoms, contact your doctor or seek medical attention immediately:
Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin (with or without fever)
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Signs of a severe skin reaction (Stevens-Johnson syndrome/toxic epidermal necrolysis), such as:
+ Red, swollen, blistered, or peeling skin (with or without fever)
+ Red or irritated eyes
+ Sores in the mouth, throat, nose, or eyes
Signs of liver problems, including:
+ Dark urine
+ Tiredness
+ Decreased appetite
+ Upset stomach or stomach pain
+ Light-colored stools
+ Vomiting
+ Yellow skin or eyes
Fever, chills, or sore throat
Unexplained bruising or bleeding
Feeling extremely tired or weak
Confusion
Hallucinations (seeing or hearing things that are not there)
Difficulty urinating or changes in urine output
Seizures
Severe dizziness
Severe headache
Severe joint pain
Vaginal itching or discharge
Important Note: Diarrhea is a common side effect of antibiotics. However, in rare cases, a severe form of diarrhea called C. diff-associated diarrhea (CDAD) may occur. This can lead to a life-threatening bowel problem. If you experience stomach pain, cramps, or very loose, watery, or bloody stools, contact your doctor immediately. Before treating diarrhea, consult with your doctor.
Other Possible Side Effects
Most people do not experience severe side effects, and some may not have any side effects at all. However, if you notice any of the following side effects or any other unusual symptoms, contact your doctor or seek medical attention:
Stomach pain or diarrhea
Upset stomach or vomiting
Reporting Side Effects
This is not an exhaustive list of possible side effects. If you have questions or concerns about side effects, contact your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
Seek Immediate Medical Attention If You Experience:
- Signs of a severe allergic reaction: hives, difficulty breathing, swelling of your face, lips, tongue, or throat.
- Severe stomach pain, watery or bloody diarrhea (even if it occurs months after your last dose).
- Easy bruising or bleeding, unusual weakness.
- Fever, swollen glands, rash or itching, joint pain, or general ill feeling (signs of a severe skin reaction).
- Yellowing of the skin or eyes (jaundice), dark urine, clay-colored stools (signs of liver problems).
- Little or no urination.
Before Using This Medicine
Before Taking This Medication: Important Information to Share with Your Doctor
It is essential to inform your doctor about the following:
Any allergies you have, including allergies to this medication, its components, or other substances, such as foods or drugs. Be sure to describe the symptoms you experienced.
If you are currently taking probenecid, as this may interact with the medication.
Additionally, to ensure safe treatment, provide your doctor and pharmacist with a comprehensive list of:
All prescription and over-the-counter (OTC) medications you are taking
Any natural products or vitamins you are using
* Your existing health problems
This information will help your doctor determine if it is safe for you to take this medication with your other drugs and health conditions. Never start, stop, or adjust the dose of any medication without first consulting your doctor to confirm it is safe to do so.
It is essential to inform your doctor about the following:
Any allergies you have, including allergies to this medication, its components, or other substances, such as foods or drugs. Be sure to describe the symptoms you experienced.
If you are currently taking probenecid, as this may interact with the medication.
Additionally, to ensure safe treatment, provide your doctor and pharmacist with a comprehensive list of:
All prescription and over-the-counter (OTC) medications you are taking
Any natural products or vitamins you are using
* Your existing health problems
This information will help your doctor determine if it is safe for you to take this medication with your other drugs and health conditions. Never start, stop, or adjust the dose of any medication without first consulting your doctor to confirm it is safe to do so.
Precautions & Cautions
It is essential to inform all your healthcare providers, including doctors, nurses, pharmacists, and dentists, that you are taking this medication. If you are taking this drug for an extended period, your doctor may recommend regular blood tests to monitor your condition.
If you have diabetes and regularly test your urine for glucose, consult with your doctor to determine the most suitable testing method for you, as this medication may affect the accuracy of certain tests. Additionally, be sure to notify all your healthcare providers and laboratory personnel that you are taking this medication, as it may impact the results of some lab tests.
Do not take this medication for longer than prescribed, as this may increase the risk of a secondary infection.
If you are pregnant, planning to become pregnant, or are breastfeeding, it is crucial to discuss the potential benefits and risks of this medication with your doctor to ensure the best possible outcome for you and your baby.
If you have diabetes and regularly test your urine for glucose, consult with your doctor to determine the most suitable testing method for you, as this medication may affect the accuracy of certain tests. Additionally, be sure to notify all your healthcare providers and laboratory personnel that you are taking this medication, as it may impact the results of some lab tests.
Do not take this medication for longer than prescribed, as this may increase the risk of a secondary infection.
If you are pregnant, planning to become pregnant, or are breastfeeding, it is crucial to discuss the potential benefits and risks of this medication with your doctor to ensure the best possible outcome for you and your baby.
Overdose Information
Overdose Symptoms:
- Nausea
- Vomiting
- Diarrhea
- Abdominal pain
- Hematuria (blood in urine)
- In rare cases, seizures (especially in patients with renal impairment)
What to Do:
In case of suspected overdose, seek immediate medical attention or call a poison control center (e.g., 1-800-222-1222). Management is primarily supportive, including gastric lavage or activated charcoal if ingestion was recent. Hemodialysis may be useful in removing cephalexin from the blood, especially in patients with renal impairment.
Drug Interactions
Monitoring
Baseline Monitoring
Culture and Sensitivity
Rationale: To identify the causative pathogen and determine its susceptibility to cephalexin, guiding appropriate therapy.
Timing: Prior to initiation of therapy, if clinically indicated.
Renal Function (CrCl, SCr)
Rationale: To assess baseline kidney function and guide dose adjustments in patients with renal impairment.
Timing: Prior to initiation of therapy, especially in elderly patients or those with known renal disease.
Routine Monitoring
Clinical Response
Frequency: Daily during acute treatment
Target: Resolution of signs and symptoms of infection
Action Threshold: Lack of improvement or worsening symptoms may indicate treatment failure, resistance, or alternative diagnosis.
Signs of Allergic Reaction (rash, pruritus, urticaria)
Frequency: Daily
Target: Absence of allergic symptoms
Action Threshold: Development of rash, hives, or other allergic symptoms requires immediate discontinuation.
Bowel Habits (for C. difficile-associated diarrhea)
Frequency: Daily
Target: Normal bowel movements
Action Threshold: Development of severe, persistent diarrhea, especially with abdominal pain and fever, warrants investigation for C. difficile.
Renal Function (SCr, CrCl)
Frequency: Periodically, especially in patients with pre-existing renal impairment or on prolonged therapy.
Target: Stable renal function
Action Threshold: Significant decline in renal function may necessitate dose adjustment.
Symptom Monitoring
- Skin rash or hives
- Itching
- Swelling of face, lips, tongue, or throat
- Difficulty breathing or swallowing
- Severe or watery diarrhea
- Abdominal pain or cramps
- Nausea or vomiting
- Unusual tiredness or weakness
- Yellowing of skin or eyes (jaundice)
- Dark urine
- Unusual bleeding or bruising
Special Patient Groups
Pregnancy
Cephalexin is generally considered safe for use during pregnancy (Category B). Animal reproduction studies have not demonstrated a risk to the fetus, and there are no adequate and well-controlled studies in pregnant women. It is often used for common infections in pregnancy.
Trimester-Specific Risks:
First Trimester:
No increased risk of major birth defects observed.
Second Trimester:
No increased risk of adverse outcomes observed.
Third Trimester:
No increased risk of adverse outcomes observed.
Lactation
Cephalexin is excreted in small amounts into breast milk. It is generally considered compatible with breastfeeding (Lactation Risk L1). Monitor breastfed infants for potential adverse effects such as diarrhea, candidiasis (thrush), or allergic reactions (e.g., rash).
Infant Risk:
Low risk; generally considered safe.
Pediatric Use
Dosing is weight-based and should be carefully calculated. Oral suspension is available for easier administration in younger children. Monitor for gastrointestinal side effects and allergic reactions. Not recommended for neonates without specific guidance.
Geriatric Use
No specific dose adjustment is needed based solely on age, but renal function should be assessed, as elderly patients are more likely to have age-related decline in kidney function. Dose adjustments should be made based on creatinine clearance.
Clinical Information
Clinical Pearls
- Cephalexin is a first-generation cephalosporin, primarily active against Gram-positive bacteria (e.g., Staphylococcus aureus, Streptococcus pyogenes) and some Gram-negative bacteria (e.g., E. coli, Klebsiella pneumoniae, Proteus mirabilis).
- It is a common choice for skin and soft tissue infections (e.g., cellulitis, impetigo), streptococcal pharyngitis, and uncomplicated urinary tract infections.
- Cephalexin is NOT effective against MRSA (Methicillin-Resistant Staphylococcus aureus) or most anaerobic bacteria.
- Patients with a history of penicillin allergy should be carefully evaluated due to potential cross-reactivity (estimated at 1-10%, though often lower for first-generation cephalosporins).
- Advise patients to complete the full course of therapy to prevent the development of antibiotic resistance.
- Can cause C. difficile-associated diarrhea (CDAD), ranging from mild diarrhea to fatal colitis. Patients developing severe diarrhea during or after treatment should be evaluated for CDAD.
Alternative Therapies
- Other first-generation cephalosporins (e.g., Cefazolin IV)
- Penicillins (e.g., Amoxicillin, Dicloxacillin, Penicillin V)
- Macrolides (e.g., Azithromycin, Clarithromycin, Erythromycin) for penicillin-allergic patients
- Clindamycin (for skin/soft tissue infections, including some MRSA strains, but with higher C. diff risk)
- Trimethoprim-sulfamethoxazole (for UTIs, some skin infections)
Cost & Coverage
Average Cost:
Highly variable, typically low per 30 capsules
Generic Available:
Yes
Insurance Coverage:
Tier 1 or Tier 2 (preferred generic)
General Drug Facts
If your symptoms or health issues persist or worsen, it is essential to contact your doctor promptly. To ensure safe and effective treatment, never share your medication with others or take someone else's medication. Some medications may come with an additional patient information leaflet, so it is a good idea to consult with your pharmacist. If you have any questions or concerns about this medication, do not hesitate to discuss them with your doctor, nurse, pharmacist, or other healthcare provider. In the event of a suspected overdose, immediately call your local poison control center or seek emergency medical attention. When seeking help, be prepared to provide detailed information about the overdose, including the medication taken, the amount, and the time it occurred.