Keflex 250mg/5ml Susp 100ml
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, urinary tract, bones, and ears. It works by stopping the growth of bacteria. It is important to take the full course of medication as prescribed, even if you feel better, to prevent the infection from returning.
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.
Before taking a dose, shake the liquid well. Measure liquid doses carefully using the measuring device that comes with the medication. If one is not provided, ask your pharmacist for a suitable measuring device.
Storing and Disposing of Your Medication
Store the medication in the refrigerator and discard any unused portion after 2 weeks. Keep the lid tightly closed and store all medications in a safe place, out of the reach of children and pets.
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 scheduled dose, skip the missed dose and resume your regular dosing schedule. Do not take two doses at the same time or take extra doses.
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.
Before taking a dose, shake the liquid well. Measure liquid doses carefully using the measuring device that comes with the medication. If one is not provided, ask your pharmacist for a suitable measuring device.
Storing and Disposing of Your Medication
Store the medication in the refrigerator and discard any unused portion after 2 weeks. Keep the lid tightly closed and store all medications in a safe place, out of the reach of children and pets.
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 scheduled dose, skip the missed dose and resume your regular dosing schedule. Do not take two doses at the same time or take extra doses.
Lifestyle & Tips
- Take with food or milk if stomach upset occurs.
- Shake the oral suspension well before each use.
- Use an accurate measuring spoon or cup for the liquid form.
- Do not share this medication with others.
- Avoid alcohol if it causes stomach upset, though no direct interaction is noted.
Available Forms & Alternatives
Dosing & Administration
Adult Dosing
Standard Dose:
250 mg to 500 mg every 6 hours or 500 mg every 12 hours
Dose Range:
250 - 1000 mg
Condition-Specific Dosing:
Mild to moderate infections:
250 mg every 6 hours or 500 mg every 12 hours
Skin and skin structure infections:
500 mg every 12 hours
Streptococcal pharyngitis:
250 mg every 6 hours or 500 mg every 12 hours for at least 10 days
Urinary tract infections:
250 mg every 6 hours or 500 mg every 12 hours
Bone infections:
250 mg to 500 mg every 6 hours
Pediatric Dosing
Neonatal:
Not established (use with caution, consult specialist)
Infant:
25 to 50 mg/kg/day in divided doses every 6 to 12 hours (max 100 mg/kg/day or 4 g/day)
Child:
25 to 50 mg/kg/day in divided doses every 6 to 12 hours (max 100 mg/kg/day or 4 g/day)
Adolescent:
25 to 50 mg/kg/day in divided doses every 6 to 12 hours (max 100 mg/kg/day or 4 g/day) or adult dosing if weight/age appropriate
Dose Adjustments
Renal Impairment:
Mild:
CrCl 30-59 mL/min: No adjustment typically needed, but consider extending dosing interval to q8-12h for severe infections.
Moderate:
CrCl 15-29 mL/min: 250 mg every 8-12 hours (max 500 mg every 8-12 hours)
Severe:
CrCl <15 mL/min: 250 mg every 12-24 hours (max 500 mg every 12-24 hours)
Dialysis:
Hemodialysis: 250 mg to 500 mg after each dialysis session. Peritoneal Dialysis: 250 mg every 12 hours.
Hepatic Impairment:
Mild:
No adjustment needed
Moderate:
No adjustment needed
Severe:
No adjustment needed
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 inhibition of cell wall biosynthesis and eventually bacterial cell lysis.
Pharmacokinetics
Absorption:
Bioavailability:
>90%
Tmax:
Approximately 1 hour
FoodEffect:
Food may delay absorption but does not significantly reduce the total amount absorbed.
Distribution:
Vd:
Approximately 0.26 L/kg
ProteinBinding:
Approximately 10-15%
CnssPenetration:
Limited (does not achieve therapeutic concentrations in CSF)
Elimination:
HalfLife:
Approximately 0.5 to 1.2 hours (prolonged in renal impairment)
Clearance:
Approximately 210 mL/min (renal clearance)
ExcretionRoute:
Renal (glomerular filtration and tubular secretion)
Unchanged:
>90%
Pharmacodynamics
OnsetOfAction:
Rapid
PeakEffect:
Approximately 1 hour (plasma concentration)
DurationOfAction:
Approximately 6-8 hours (based on dosing interval)
Safety & Warnings
Side Effects
Urgent Side Effects: Seek Medical Help Immediately
Although rare, some individuals may experience severe and potentially life-threatening side effects while taking this medication. If you encounter any of the following symptoms, contact your doctor or seek medical attention right away:
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
+ 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), including:
+ 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, such as:
+ 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, particularly 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 and Less Severe Side Effects
Most medications can cause side effects, but many people experience none or only mild symptoms. If you encounter any of the following side effects or any other unusual symptoms, contact your doctor or seek medical attention if they bother you or persist:
Stomach pain or diarrhea
* Upset stomach or vomiting
Reporting Side Effects
This list is not exhaustive, and you may experience other side effects not mentioned here. If you have questions or concerns about side effects, consult 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 individuals may experience severe and potentially life-threatening side effects while taking this medication. If you encounter any of the following symptoms, contact your doctor or seek medical attention right away:
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
+ 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), including:
+ 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, such as:
+ 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, particularly 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 and Less Severe Side Effects
Most medications can cause side effects, but many people experience none or only mild symptoms. If you encounter any of the following side effects or any other unusual symptoms, contact your doctor or seek medical attention if they bother you or persist:
Stomach pain or diarrhea
* Upset stomach or vomiting
Reporting Side Effects
This list is not exhaustive, and you may experience other side effects not mentioned here. If you have questions or concerns about side effects, consult 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:
- Severe allergic reaction (hives, difficulty breathing, swelling of face/lips/tongue/throat)
- Severe or watery diarrhea (especially if persistent or bloody)
- Unusual bleeding or bruising
- Yellowing of skin or eyes (jaundice)
- Dark urine, pale stools
- Fever, sore throat, or chills (signs of new infection)
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 medications and health conditions. Never start, stop, or change the dose of any medication without first consulting 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 medications and health conditions. Never start, stop, or change the dose of any medication without first consulting your doctor.
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 a secondary infection. If you are pregnant, planning to become pregnant, or are breastfeeding, discuss the potential benefits and risks of this medication with your doctor to make an informed decision about your treatment.
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 a secondary infection. If you are pregnant, planning to become pregnant, or are breastfeeding, discuss the potential benefits and risks of this medication with your doctor to make an informed decision about your treatment.
Overdose Information
Overdose Symptoms:
- Nausea
- Vomiting
- Epigastric distress
- Diarrhea
- Hematuria (blood in urine)
- Rarely, seizures (especially in patients with renal impairment)
What to Do:
Seek immediate medical attention or call a poison control center (e.g., 1-800-222-1222). Treatment is supportive; hemodialysis may be useful in severe cases of renal impairment.
Drug Interactions
Major Interactions
- Metformin (increased metformin plasma concentrations, monitor for lactic acidosis)
- Probenecid (decreased renal excretion of cephalexin, leading to increased and prolonged plasma concentrations)
Moderate Interactions
- Warfarin (potential for increased INR/bleeding risk, monitor INR)
- Live bacterial vaccines (e.g., BCG, typhoid vaccine; may reduce therapeutic effect of vaccine)
- Cholera vaccine (may reduce efficacy of vaccine)
Monitoring
Baseline Monitoring
Culture and Susceptibility
Rationale: To confirm bacterial pathogen and its susceptibility to cephalexin, guiding appropriate therapy.
Timing: Prior to initiation of therapy, if clinically indicated.
Renal Function (BUN, Creatinine)
Rationale: To establish baseline renal function, especially in elderly patients or those with pre-existing renal impairment, as cephalexin is primarily renally eliminated.
Timing: Prior to initiation of therapy in at-risk patients.
Routine Monitoring
Signs and Symptoms of Infection Resolution
Frequency: Daily
Target: Improvement in fever, pain, inflammation, etc.
Action Threshold: Lack of improvement or worsening symptoms may indicate treatment failure or resistant organism.
Renal Function (BUN, Creatinine)
Frequency: Periodically, as clinically indicated (e.g., weekly)
Target: Within patient's baseline or acceptable limits
Action Threshold: Significant increase may require dose adjustment or discontinuation.
Bowel Habits (for C. difficile-associated diarrhea)
Frequency: Daily
Target: Normal bowel movements
Action Threshold: Persistent or severe diarrhea, especially with abdominal pain/fever, warrants C. difficile testing.
Symptom Monitoring
- Rash or hives (signs of allergic reaction)
- Difficulty breathing or swallowing (signs of severe allergic reaction)
- Severe or persistent diarrhea (may indicate Clostridioides difficile-associated diarrhea)
- Nausea, vomiting, abdominal pain
- Vaginal itching or discharge (yeast infection)
- Unusual bruising or bleeding (rare, with warfarin interaction)
Special Patient Groups
Pregnancy
Cephalexin is generally considered safe for use during pregnancy (Pregnancy Category B). Animal studies 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:
Generally considered low risk; no evidence of increased risk of major birth defects.
Second Trimester:
Generally considered low risk.
Third Trimester:
Generally considered low risk; no evidence of adverse effects on fetal development or labor/delivery.
Lactation
Cephalexin is excreted in low concentrations in human milk. It is generally considered compatible with breastfeeding (Lactation Risk L2).
Infant Risk:
Low risk. Monitor breastfed infants for potential adverse effects such as diarrhea, candidiasis (thrush, diaper rash), or allergic reactions (rash).
Pediatric Use
Dosing is weight-based. Safety and efficacy established in pediatric patients. Oral suspension formulation is suitable for this population. Close monitoring for adverse effects is recommended.
Geriatric Use
No specific dose adjustment is needed based on age alone, but dose adjustment is necessary for age-related decreases in renal function. Monitor renal function closely in elderly patients.
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 commonly used for skin and soft tissue infections, urinary tract infections, streptococcal pharyngitis, and certain bone infections.
- Not effective against MRSA (Methicillin-resistant Staphylococcus aureus) or Pseudomonas aeruginosa.
- Patients should be advised to complete the entire course of therapy, even if symptoms improve, to prevent the development of antibiotic resistance.
- Can cause a false-positive direct Coombs' test.
Alternative Therapies
- Other first-generation cephalosporins (e.g., Cefazolin - IV)
- Penicillins (e.g., Amoxicillin, Dicloxacillin, Penicillin V - depending on pathogen and site of infection)
- Macrolides (e.g., Azithromycin, Clarithromycin - for penicillin-allergic patients, depending on pathogen)
- Clindamycin (for skin/soft tissue infections, including some MRSA strains, but different spectrum)
- Trimethoprim/Sulfamethoxazole (for UTIs, some skin infections)
Cost & Coverage
Average Cost:
Varies widely, typically low per 100ml suspension
Generic Available:
Yes
Insurance Coverage:
Tier 1 or 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 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 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.