Cephalexin 250mg Tablets
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 available 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 available 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 cephalexin 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, take it with food or milk.
- Drink plenty of fluids while taking this medication.
- Avoid alcohol consumption, as it may worsen gastrointestinal side effects.
- Do not share your medication with others, even if they have similar symptoms.
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
Dose Range:
250 - 1000 mg
Condition-Specific Dosing:
mildToModerateInfections:
250 mg every 6 hours
severeInfections:
500 mg every 6 hours or 1 g every 12 hours
skinAndSkinStructureInfections:
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
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)
Adolescent:
25-50 mg/kg/day in divided doses every 6-12 hours (max 100 mg/kg/day or adult dose)
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
Severe:
CrCl <15 mL/min: 250 mg every 12-24 hours
Dialysis:
Hemodialysis: 250 mg initially, then 250 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 first-generation cephalosporin antibiotic. It is bactericidal and acts by inhibiting bacterial cell wall synthesis. It binds to penicillin-binding proteins (PBPs) located inside the bacterial cell wall, which interferes with the transpeptidation reaction of peptidoglycan synthesis, a crucial step in bacterial cell wall formation. This leads to the disruption of the cell wall, resulting in bacterial cell lysis and death.
Pharmacokinetics
Absorption:
Bioavailability:
Approximately 90%
Tmax:
1 hour (fasted state)
FoodEffect:
Food may delay absorption but does not significantly affect the total amount absorbed.
Distribution:
Vd:
0.26 L/kg
ProteinBinding:
Approximately 10-15%
CnssPenetration:
Limited (does not achieve therapeutic concentrations in CSF unless meninges are inflamed)
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 hour 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 or seek immediate medical attention:
Signs of an allergic reaction, such as:
+ Rash or hives
+ Itching
+ Red, swollen, blistered, or peeling skin (with or without fever)
+ Wheezing
+ Tightness in the chest or throat
+ Difficulty 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
+ Fatigue
+ 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
Diarrhea, especially if it is severe, bloody, or accompanied by stomach pain or cramps (a rare but potentially life-threatening condition called C. diff-associated diarrhea or CDAD may occur)
Common Side Effects
Most people experience few or no side effects while taking this medication. However, some common side effects may occur, including:
Stomach pain or diarrhea
Upset stomach or vomiting
If any of these side effects or other symptoms bother you or do not go away, contact your doctor for advice.
Reporting Side Effects
If you have questions or concerns about side effects, you can:
Contact your doctor for medical advice
Report side effects to the FDA at 1-800-332-1088
Submit a report 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 or seek immediate medical attention:
Signs of an allergic reaction, such as:
+ Rash or hives
+ Itching
+ Red, swollen, blistered, or peeling skin (with or without fever)
+ Wheezing
+ Tightness in the chest or throat
+ Difficulty 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
+ Fatigue
+ 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
Diarrhea, especially if it is severe, bloody, or accompanied by stomach pain or cramps (a rare but potentially life-threatening condition called C. diff-associated diarrhea or CDAD may occur)
Common Side Effects
Most people experience few or no side effects while taking this medication. However, some common side effects may occur, including:
Stomach pain or diarrhea
Upset stomach or vomiting
If any of these side effects or other symptoms bother you or do not go away, contact your doctor for advice.
Reporting Side Effects
If you have questions or concerns about side effects, you can:
Contact your doctor for medical advice
Report side effects to the FDA at 1-800-332-1088
Submit a report online at https://www.fda.gov/medwatch
Seek Immediate Medical Attention If You Experience:
- Signs of a severe allergic reaction: rash, hives, itching, swelling of the face, lips, tongue, or throat, difficulty breathing or swallowing, dizziness.
- Severe, watery, or bloody diarrhea (with or without fever and stomach cramps) that occurs during or after treatment, which could be a sign of Clostridioides difficile-associated diarrhea (CDAD).
- New or worsening symptoms of infection.
- Unusual bruising or bleeding.
- Yellowing of the skin or eyes (jaundice).
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 certain lab tests.
Do not take this medication for longer than prescribed, as this can increase the risk of developing 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 certain lab tests.
Do not take this medication for longer than prescribed, as this can increase the risk of developing 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
- Stomach pain
- Diarrhea
- Hematuria (blood in urine)
- Kidney dysfunction (rare)
- Seizures (rare)
What to Do:
In case of overdose, seek immediate medical attention or call a poison control center. The national poison control center hotline is 1-800-222-1222. Treatment is generally supportive; hemodialysis may be useful in severe cases.
Drug Interactions
Major Interactions
Moderate Interactions
- Probenecid (decreased renal tubular secretion of cephalexin, leading to increased and prolonged cephalexin concentrations)
- Live bacterial vaccines (e.g., typhoid vaccine, may reduce efficacy)
- Oral contraceptives (theoretical risk of reduced efficacy, though not well-established for cephalexin)
Monitoring
Baseline Monitoring
Renal function (serum creatinine, BUN, CrCl)
Rationale: Cephalexin is primarily renally excreted; dosage adjustments are necessary in patients with impaired renal function.
Timing: Prior to initiation of therapy, especially in elderly patients or those with known renal impairment.
Routine Monitoring
Clinical response to therapy (e.g., resolution of fever, reduction in signs/symptoms of infection)
Frequency: Daily during acute phase, then as clinically indicated
Target: Improvement or resolution of symptoms
Action Threshold: Lack of improvement or worsening symptoms may indicate treatment failure, resistance, or alternative diagnosis.
Signs and symptoms 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: Development of new infections, especially C. difficile-associated diarrhea, requires immediate evaluation and management.
Renal function (serum creatinine, BUN)
Frequency: Periodically during prolonged therapy or in patients with pre-existing renal impairment
Target: Stable renal function
Action Threshold: Significant increase in creatinine/BUN may necessitate dose adjustment or discontinuation.
Symptom Monitoring
- Rash
- Hives
- Itching
- Swelling (face, lips, tongue, throat)
- Difficulty breathing or swallowing (signs of allergic reaction)
- Severe diarrhea (watery or bloody stools)
- Abdominal cramps
- Fever (signs of C. difficile infection)
- Unusual tiredness or weakness
- Yellowing of skin or eyes (jaundice)
- Dark urine
- Pale stools
Special Patient Groups
Pregnancy
Cephalexin is generally considered safe for use during pregnancy (Pregnancy Category B). Animal reproduction studies have shown no evidence of harm to the fetus. Human studies are limited but have not shown an increased risk of birth defects.
Trimester-Specific Risks:
First Trimester:
Low risk; no evidence of increased risk of major birth defects.
Second Trimester:
Low risk.
Third Trimester:
Low risk.
Lactation
Cephalexin is excreted in small amounts into breast milk. It is generally considered compatible with breastfeeding (Lactation Risk L1).
Infant Risk:
Low risk. Potential for alteration of infant gut flora, diarrhea, or allergic sensitization. Monitor breastfed infants for signs of diarrhea, candidiasis (thrush, diaper rash), or allergic reactions (rash).
Pediatric Use
Dosing is weight-based and varies by indication. Safety and efficacy have been established for pediatric patients. Close monitoring for adverse effects, especially gastrointestinal disturbances and allergic reactions, is important.
Geriatric Use
No specific dose adjustment is needed based solely on age. However, elderly patients are more likely to have decreased renal function, which necessitates careful monitoring of renal function and appropriate dose adjustment based on creatinine clearance. They may also be more susceptible to 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 not effective against MRSA.
- It is a common choice for skin and soft tissue infections, uncomplicated urinary tract infections, and streptococcal pharyngitis.
- Advise patients to complete the full course of therapy, even if symptoms improve, to prevent the development of antibiotic resistance.
- Counsel patients on the signs and symptoms of C. difficile-associated diarrhea, which can occur during or even weeks after antibiotic therapy.
- Liquid formulations should be shaken well before each use and stored in the refrigerator. Discard any unused portion after 14 days.
Alternative Therapies
- Amoxicillin (for susceptible infections)
- Amoxicillin/clavulanate (for broader spectrum, including beta-lactamase producing strains)
- Cefadroxil (another first-generation cephalosporin, often dosed less frequently)
- Cefuroxime (second-generation cephalosporin, broader Gram-negative coverage)
- Clindamycin (for skin/soft tissue infections, especially if MRSA is suspected or patient is penicillin allergic)
- Trimethoprim/sulfamethoxazole (for UTIs, some skin infections)
Cost & Coverage
Average Cost:
Varies widely per 30 tablets
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 it's a good idea to check with your pharmacist. 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 information about what was taken, the amount, and the time it happened.