Keflex 125mg/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 skin infections, ear infections, strep throat, and urinary tract infections. It works by killing the bacteria that cause these infections.
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 medication well. To ensure accurate dosing, use 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 location, 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 is 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 medication well. To ensure accurate dosing, use 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 location, 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 is 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 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.
- Shake the oral suspension well before each use.
- Measure the liquid medicine carefully using the provided measuring spoon or cup, not a household spoon.
- Cephalexin can be taken with or without food. If it causes stomach upset, try taking it with food or milk.
- Store the suspension in the refrigerator and discard any unused portion after 14 days (or as directed by pharmacist).
- Avoid alcohol while taking antibiotics, as it can worsen side effects like stomach upset.
Available Forms & Alternatives
Dosing & Administration
Adult Dosing
Standard Dose:
250 mg every 6 hours or 500 mg every 12 hours
Dose Range:
250 - 1000 mg
Condition-Specific Dosing:
Skin and Skin Structure Infections:
250 mg every 6 hours or 500 mg every 12 hours
Streptococcal Pharyngitis:
250 mg every 6 hours or 500 mg every 12 hours for 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 caution, consult specific guidelines)
Infant:
25-50 mg/kg/day in divided doses (every 6 or 12 hours)
Child:
25-50 mg/kg/day in divided doses (every 6 or 12 hours); for otitis media, 75-100 mg/kg/day in divided doses
Adolescent:
25-50 mg/kg/day in divided doses (every 6 or 12 hours), up to maximum 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, thereby inhibiting the transpeptidation stage of peptidoglycan synthesis. This leads to the disruption of the cell wall, osmotic instability, and ultimately cell lysis and death.
Pharmacokinetics
Absorption:
Bioavailability:
Approximately 90%
Tmax:
1 hour (fasting)
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); significantly prolonged in renal impairment
Clearance:
Approximately 210 mL/min (renal clearance)
ExcretionRoute:
Renal (glomerular filtration and tubular secretion)
Unchanged:
Approximately 70-90% of the dose is excreted unchanged in the urine within 8 hours.
Pharmacodynamics
OnsetOfAction:
Rapid
PeakEffect:
Within 1 hour of oral administration
DurationOfAction:
Approximately 6-8 hours (dictates dosing frequency)
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 signs or symptoms, contact your doctor or seek medical attention immediately:
Allergic reaction symptoms, 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), including:
+ Red, swollen, blistered, or peeling skin (with or without fever)
+ Red or irritated eyes
+ Sores in the mouth, throat, nose, or eyes
Indications of liver problems, such as:
+ 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
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 and Less Severe Side Effects
Most people taking this medication will not experience severe side effects. However, some may encounter mild or moderate side effects, 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 guidance.
Reporting Side Effects
If you have questions or concerns about side effects, call 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 signs or symptoms, contact your doctor or seek medical attention immediately:
Allergic reaction symptoms, 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), including:
+ Red, swollen, blistered, or peeling skin (with or without fever)
+ Red or irritated eyes
+ Sores in the mouth, throat, nose, or eyes
Indications of liver problems, such as:
+ 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
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 and Less Severe Side Effects
Most people taking this medication will not experience severe side effects. However, some may encounter mild or moderate side effects, 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 guidance.
Reporting Side Effects
If you have questions or concerns about side effects, call 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, hives, itching, swelling (especially of the face, lips, tongue, or throat), severe dizziness, trouble breathing.
- Severe or watery diarrhea, especially if it contains blood or mucus, which may occur up to several weeks after stopping the medication (could be C. difficile infection).
- Unusual bruising or bleeding.
- Yellowing of the skin or eyes (jaundice).
- Signs of kidney problems: changes in urination, swelling in ankles or feet.
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 change 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 change 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 interfere with certain test results. Additionally, be sure to notify all your healthcare providers and laboratory personnel that you are taking this medication, as it may affect the accuracy of certain 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 interfere with certain test results. Additionally, be sure to notify all your healthcare providers and laboratory personnel that you are taking this medication, as it may affect the accuracy of certain 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
- Epigastric distress
- Diarrhea
- Hematuria (blood in urine)
- In rare cases, seizures (especially in patients with renal impairment)
What to Do:
Call 1-800-222-1222 (Poison Control). Treatment is primarily supportive. Gastric lavage may be indicated if performed within 1 hour of ingestion. Hemodialysis may be useful in accelerating the removal of cephalexin from the blood, especially in patients with renal impairment.
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 therapeutic effect of vaccine)
Monitoring
Baseline Monitoring
Renal function (CrCl, BUN, Creatinine)
Rationale: Cephalexin is primarily renally eliminated; dose adjustment is necessary in renal impairment.
Timing: Prior to initiation of therapy, especially in elderly or patients with known renal issues.
Routine Monitoring
Clinical response to therapy (e.g., resolution of infection symptoms)
Frequency: Daily
Target: Improvement in symptoms (e.g., reduced fever, pain, inflammation)
Action Threshold: Lack of improvement or worsening symptoms after 2-3 days 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; consider antifungal or C. difficile treatment.
Renal function (BUN, Creatinine)
Frequency: Periodically, especially in prolonged therapy or patients with pre-existing renal impairment
Target: Stable renal function
Action Threshold: Significant increase in BUN/Creatinine; consider dose adjustment or alternative therapy.
Symptom Monitoring
- Allergic reactions (rash, itching, hives, swelling of face/lips/tongue, difficulty breathing)
- Gastrointestinal disturbances (nausea, vomiting, diarrhea, abdominal pain)
- Severe or persistent diarrhea (may indicate Clostridioides difficile-associated diarrhea)
- Headache, dizziness
- Joint pain
Special Patient Groups
Pregnancy
Cephalexin is generally considered safe for use during pregnancy (Pregnancy Category B). Animal reproduction studies have not shown a risk to the fetus, and there are no adequate and well-controlled studies in pregnant women. It is often used for common infections during pregnancy.
Trimester-Specific Risks:
First Trimester:
Low risk, no evidence of increased congenital anomalies.
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). Monitor breastfed infants for potential adverse effects such as diarrhea, candidiasis (thrush, diaper rash), or allergic reactions.
Infant Risk:
Low risk. Potential for minor gastrointestinal upset or sensitization in the infant.
Pediatric Use
Widely used and generally safe in pediatric patients. Dosing is weight-based (mg/kg/day) and adjusted for age and severity of infection. Neonatal use requires careful consideration and specific guidelines due to immature renal function.
Geriatric Use
Use with caution in elderly patients due to the higher likelihood of decreased renal function. Renal function should be assessed, and dosage adjustments made accordingly to prevent accumulation and potential toxicity.
Clinical Information
Clinical Pearls
- Cephalexin is a first-generation cephalosporin, primarily effective 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 UTIs, and streptococcal pharyngitis.
- Always complete the full course of therapy, even if symptoms improve, to prevent the development of antibiotic resistance.
- Oral suspension must be refrigerated after reconstitution and discarded after 14 days.
- Patients with a history of severe penicillin allergy (e.g., anaphylaxis) should generally avoid cephalexin due to potential cross-reactivity, although the risk is low (around 1-5%) for first-generation cephalosporins.
Alternative Therapies
- Amoxicillin/Clavulanate (Augmentin) - broader spectrum, including beta-lactamase producing strains
- Dicloxacillin (for penicillinase-producing staphylococci)
- Clindamycin (for skin infections, especially if penicillin allergy or MRSA concern)
- Trimethoprim/Sulfamethoxazole (Bactrim) - for UTIs, some skin infections
- Other cephalosporins (e.g., cefazolin IV for similar spectrum, cefuroxime for broader Gram-negative coverage)
Cost & Coverage
Average Cost:
$15 - $40 per 100ml of 125mg/5ml suspension
Generic Available:
Yes
Insurance Coverage:
Tier 1 (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 check with your pharmacist for more information. 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 details about the overdose, including the medication taken, the amount, and the time it occurred.