Cephalexin 500mg 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 used to treat various bacterial infections, such as those of the skin, ears, throat, and urinary tract. It works by stopping the growth of bacteria. It is not effective against viral infections like the common cold or flu.
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 want to check if there are 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 want to check if there are 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.
- 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, as it may worsen stomach upset.
Available Forms & Alternatives
Available Strengths:
- Cephalexin 250mg/5ml Susp 100ml
- Cephalexin 250mg/5ml Susp 200ml
- Cephalexin 125mg/5ml Susp 100ml
- Cephalexin 125mg/5ml Susp 200ml
- Cephalexin 250mg Capsules
- Cephalexin 500mg Capsules
- Cephalexin 250mg Tablets
- Cephalexin 500mg Tablets
- Cephalexin 750mg Capsules
- Cephalexin 125mg/5ml Susp 100ml
- Cephalexin 500mg Tablets
- Cephalexin 250mg Tablets
Dosing & Administration
Adult Dosing
Standard Dose:
250 mg to 500 mg every 6 hours or 500 mg to 1 g every 12 hours
Dose Range:
250 - 1000 mg
Condition-Specific Dosing:
mildToModerateInfections:
250 mg every 6 hours or 500 mg every 12 hours
skinAndSoftTissueInfections:
500 mg every 12 hours
streptococcalPharyngitis:
250 mg every 6 hours or 500 mg every 12 hours for 10 days
urinaryTractInfections:
250 mg every 6 hours or 500 mg every 12 hours
boneAndJointInfections:
250 mg to 500 mg every 6 hours
Pediatric Dosing
Neonatal:
Not established (use caution, consult specialist)
Infant:
25-50 mg/kg/day in divided doses every 6-12 hours (max 100 mg/kg/day)
Child:
25-50 mg/kg/day in divided doses every 6-12 hours (max 100 mg/kg/day, up to 4 g/day)
Adolescent:
Same as adult dosing (250 mg to 500 mg every 6 hours or 500 mg to 1 g every 12 hours)
Dose Adjustments
Renal Impairment:
Mild:
CrCl 30-59 mL/min: No adjustment needed for standard doses, consider extending interval for higher doses.
Moderate:
CrCl 15-29 mL/min: 250 mg every 8-12 hours or 500 mg every 12 hours.
Severe:
CrCl <15 mL/min: 250 mg every 12-24 hours or 500 mg every 24 hours.
Dialysis:
Hemodialysis: 250 mg to 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 inhibits the final transpeptidation step of peptidoglycan synthesis in the bacterial cell wall, leading to cell lysis and death.
Pharmacokinetics
Absorption:
Bioavailability:
Approximately 90%
Tmax:
1 hour (fasted), 2 hours (with food)
FoodEffect:
Food may delay absorption and peak concentrations but does not significantly affect the total amount absorbed.
Distribution:
Vd:
0.26 L/kg
ProteinBinding:
6-15%
CnssPenetration:
Limited (does not achieve therapeutic concentrations in CSF)
Elimination:
HalfLife:
0.5-1.2 hours (normal renal function)
Clearance:
Approximately 210 mL/min
ExcretionRoute:
Renal (glomerular filtration and tubular secretion)
Unchanged:
Approximately 70-90% excreted unchanged in urine within 8 hours
Pharmacodynamics
OnsetOfAction:
Rapid
PeakEffect:
Within 1-2 hours of oral administration
DurationOfAction:
Approximately 6-8 hours (based on dosing interval)
Safety & Warnings
Side Effects
Urgent Side Effects: Seek Medical Help Right Away
Although rare, some people may experience severe and potentially life-threatening side effects while taking this medication. If you notice any of the following symptoms, contact your doctor immediately or seek medical attention:
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 called C. diff-associated diarrhea (CDAD) may occur, which can lead to life-threatening bowel problems. 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
Like all medications, this drug may cause side effects. While many people do not experience any significant side effects or only have mild ones, it is essential to discuss any concerns with your doctor. If you experience any of the following side effects or any other symptoms that bother you or do not go away, contact your doctor:
Stomach pain or diarrhea
Upset stomach or vomiting
Reporting Side Effects
This list is not exhaustive, and you may experience other 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.
Although rare, some people may experience severe and potentially life-threatening side effects while taking this medication. If you notice any of the following symptoms, contact your doctor immediately or seek medical attention:
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 called C. diff-associated diarrhea (CDAD) may occur, which can lead to life-threatening bowel problems. 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
Like all medications, this drug may cause side effects. While many people do not experience any significant side effects or only have mild ones, it is essential to discuss any concerns with your doctor. If you experience any of the following side effects or any other symptoms that bother you or do not go away, contact your doctor:
Stomach pain or diarrhea
Upset stomach or vomiting
Reporting Side Effects
This list is not exhaustive, and you may experience other 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: rash, itching/swelling (especially of face/tongue/throat), severe dizziness, trouble breathing. Seek immediate medical attention.
- Severe or watery diarrhea, especially if it occurs during or after treatment, as this could be a sign of a serious intestinal infection (Clostridioides difficile-associated diarrhea).
- Unusual tiredness, yellowing eyes/skin (jaundice), dark urine (signs of liver problems, rare).
- Easy bruising or bleeding (if on blood thinners).
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 dosage 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 dosage 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 interfere with certain test results.
Be aware that this drug can affect the outcomes of some laboratory tests. Therefore, it is crucial to notify all your healthcare providers and laboratory personnel that you are taking this medication.
Do not take this medication for longer than prescribed, as this can increase the risk of developing a second infection.
If you are pregnant, planning to become pregnant, or are breastfeeding, it is vital 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 interfere with certain test results.
Be aware that this drug can affect the outcomes of some laboratory tests. Therefore, it is crucial to notify all your healthcare providers and laboratory personnel that you are taking this medication.
Do not take this medication for longer than prescribed, as this can increase the risk of developing a second infection.
If you are pregnant, planning to become pregnant, or are breastfeeding, it is vital 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
- Epigastric distress
- Diarrhea
- Hematuria (rare)
- Convulsions (rare, especially in renal impairment)
What to Do:
Call 1-800-222-1222 (Poison Control Center) or seek emergency medical attention. Treatment is supportive; hemodialysis may be useful in severe cases of renal impairment.
Drug Interactions
Monitoring
Baseline Monitoring
Renal function (BUN, serum creatinine, CrCl)
Rationale: Cephalexin is primarily renally eliminated; dose adjustment is necessary in renal impairment.
Timing: Prior to initiation, especially in elderly or patients with known renal issues.
Routine Monitoring
Clinical response to therapy (resolution of infection symptoms)
Frequency: Daily
Target: Improvement in fever, pain, inflammation
Action Threshold: Lack of improvement or worsening symptoms may indicate treatment failure or resistant organism.
Signs of superinfection (e.g., oral thrush, vaginal candidiasis, severe diarrhea)
Frequency: Throughout therapy and for several weeks post-therapy
Target: Absence of new infections
Action Threshold: Presence of new symptoms requires evaluation and appropriate treatment.
Renal function (BUN, serum creatinine)
Frequency: Periodically, especially in patients with pre-existing renal impairment or on prolonged therapy
Target: Stable renal function
Action Threshold: Significant increase in BUN/creatinine may necessitate dose adjustment or discontinuation.
Symptom Monitoring
- Rash or hives (signs of allergic reaction)
- Difficulty breathing or swallowing (signs of severe allergic reaction)
- Severe or watery diarrhea, abdominal cramps, fever (signs of Clostridioides difficile-associated diarrhea)
- Unusual bruising or bleeding (if on anticoagulants)
- Nausea, vomiting, stomach pain
Special Patient Groups
Pregnancy
Cephalexin is generally considered safe for use during pregnancy (Category B). Studies in animals have not shown harm to the fetus, and there are no adequate and well-controlled studies in pregnant women, but extensive clinical experience suggests low risk.
Trimester-Specific Risks:
First Trimester:
Low risk, generally considered compatible.
Second Trimester:
Low risk, generally considered compatible.
Third Trimester:
Low risk, generally considered compatible.
Lactation
Cephalexin is excreted in human milk in low concentrations. It is generally considered compatible with breastfeeding (L2). Monitor breastfed infants for potential adverse effects such as diarrhea, candidiasis (thrush, diaper rash), or allergic reactions (rash).
Infant Risk:
Low risk
Pediatric Use
Dosing is weight-based and well-established for infants and children. Caution is advised in neonates due to immature renal function.
Geriatric Use
No specific dose adjustment is needed based on age alone, but dose adjustment is required for age-related decline in renal function. Elderly patients may be more susceptible to adverse effects, particularly C. difficile-associated diarrhea.
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, uncomplicated urinary tract infections, and streptococcal pharyngitis.
- Instruct patients to complete the entire course of therapy, even if symptoms improve, to prevent the development of antibiotic resistance.
- Can cause a false-positive reaction for glucose in the urine using Clinitest tablets (Benedict's solution or Fehling's solution). Glucose oxidase tests (e.g., Tes-Tape, Clinistix) are not affected.
- Patients with a history of penicillin allergy should be monitored closely due to potential cross-reactivity (though generally low for first-generation cephalosporins, ~5-10%). Avoid in patients with a history of severe immediate hypersensitivity to penicillin.
Alternative Therapies
- Amoxicillin/clavulanate (Augmentin)
- Dicloxacillin
- Cefadroxil
- Clindamycin
- Trimethoprim/sulfamethoxazole (Bactrim)
- Doxycycline
Cost & Coverage
Average Cost:
Varies widely, 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's essential to contact your doctor for further guidance. To ensure your safety, never share your medication with others or take someone else's medication. Some medications may come with an additional patient information leaflet, so be sure to check with your pharmacist for more information. If you have any questions or concerns about this medication, don't hesitate to reach out to your doctor, nurse, pharmacist, or other healthcare provider. In the event of a suspected overdose, immediately call your local poison control center or seek medical attention. When seeking help, be prepared to provide details about the overdose, including the medication taken, the amount, and the time it occurred.