1. What is Cephalexin?
Cephalexin is an oral antibiotic in the cephalosporin class, specifically a first-generation cephalosporin. It is used to treat a variety of bacterial infections by interfering with the bacteria’s cell wall synthesis, leading to their death. It’s available under brand names like Keflex or as a generic in capsules, tablets, or liquid suspension.
2. What class of drug is Cephalexin?
Cephalexin belongs to the cephalosporin class of antibiotics, which are beta-lactam antibiotics similar to penicillins. As a first-generation cephalosporin, it’s particularly effective against gram-positive bacteria and some gram-negative bacteria.
3. How does Cephalexin work?
Cephalexin works by binding to penicillin-binding proteins (PBPs) in bacterial cell walls, inhibiting the final step of peptidoglycan synthesis. This weakens the cell wall, causing the bacteria to burst due to osmotic pressure. It’s bactericidal, meaning it kills bacteria rather than just stopping their growth.
4. What conditions does Cephalexin treat?
It treats infections caused by susceptible bacteria, including:
- Skin infections: E.g., cellulitis, impetigo.
- Respiratory tract infections: E.g., streptococcal pharyngitis (strep throat).
- Urinary tract infections (UTIs): E.g., cystitis.
- Bone infections: E.g., osteomyelitis.
- Ear infections: E.g., otitis media.
It’s not effective against viral infections.
5. Is Cephalexin used for anything other than infections?
Its primary use is for bacterial infections. It’s occasionally used prophylactically (e.g., before dental procedures in patients with heart conditions to prevent endocarditis), but this is less common and depends on medical guidelines.
6. How is Cephalexin taken?
Cephalexin is taken orally as capsules, tablets, or a liquid suspension. It’s usually taken every 6–12 hours (2–4 times daily) with or without food, though food may reduce stomach upset. The liquid form should be shaken well before use.
7. What is the typical dosage for adults?
For adults, the usual dose is 250–500 mg every 6 hours or 500 mg every 12 hours, depending on the infection’s severity. For severe infections, up to 4 grams daily may be prescribed, split into doses. Treatment typically lasts 7–14 days.
8. What is the dosage for children?
For children, the dose is based on weight, typically 25–50 mg/kg/day, divided into 2–4 doses. For example, a 20 kg child might take 500–1000 mg daily. Higher doses (up to 100 mg/kg/day) may be used for severe infections, under medical supervision.
9. Can Cephalexin be taken with food?
Yes, it can be taken with or without food. Taking it with food may reduce stomach irritation, though it slightly slows absorption without affecting overall effectiveness.
10. What should I do if I miss a dose?
If you miss a dose, take it as soon as you remember unless it’s nearly time for the next dose. In that case, skip the missed dose and continue the schedule. Don’t double up, as this increases side effect risks.
11. How quickly does Cephalexin work?
Cephalexin starts killing bacteria within hours, but symptom relief may take 1–2 days. Full resolution depends on the infection type and severity, often requiring the full course (7–14 days) to prevent recurrence.
12. What are the common side effects?
Common side effects include:
- Diarrhea: Due to gut flora disruption.
- Nausea: Mild stomach upset.
- Vomiting: Less common but possible.
- Rash: Mild skin reactions.
These are usually temporary and mild.
13. What are the serious side effects?
Rare but serious side effects include:
- Allergic reactions: Rash, swelling, or difficulty breathing.
- Clostridium difficile colitis: Severe diarrhea from gut overgrowth.
- Liver issues: Yellowing skin (jaundice).
- Kidney problems: Reduced urine output.
Seek immediate medical help if these occur.
14. Why does Cephalexin cause diarrhea?
It disrupts normal gut bacteria, allowing overgrowth of harmful bacteria like *Clostridium difficile*. This can lead to loose stools or, rarely, severe colitis. Probiotics may help, but consult a doctor if diarrhea persists.
15. Can Cephalexin cause allergic reactions?
Yes, especially in those allergic to cephalosporins or penicillins (due to cross-reactivity). Symptoms include rash, itching, or anaphylaxis (rare). Stop use and seek help if severe reactions occur.
16. Who should not take Cephalexin?
It’s contraindicated for:
- People allergic to cephalosporins: Or with penicillin allergy history (10% cross-reactivity risk).
- Severe kidney disease: Without dose adjustment.
Caution is needed in these cases.
17. Is Cephalexin safe during pregnancy?
Yes, it’s classified as Category B by the FDA, meaning no evidence of fetal harm in animal studies. It’s often used in pregnancy for UTIs, but only under medical supervision.
18. Can I take Cephalexin while breastfeeding?
Yes, it passes into breast milk in small amounts but is generally safe. Monitor the infant for diarrhea or rash, and consult a doctor if concerned.
19. Does Cephalexin interact with other medications?
Yes, it may interact with:
- Probenecid: Increases Cephalexin blood levels.
- Metformin: May increase metformin levels.
- Warfarin: Rarely enhances bleeding risk.
Inform your doctor of all medications.
20. Can I drink alcohol while taking Cephalexin?
Alcohol doesn’t directly interact with Cephalexin, but it may worsen side effects like nausea or delay healing. Moderate drinking is usually fine, but avoid excess.
21. Does Cephalexin cause weight gain?
No, it doesn’t affect metabolism or cause weight gain. Any weight change might relate to illness or recovery.
22. Can Cephalexin be taken at night?
Yes, it can be taken at any time, as long as doses are evenly spaced (e.g., every 6 6 or 12 hours). Nighttime dosing is fine if it fits your schedule.
23. How long do I need to take Cephalexin?
Complete the full course (usually 7–14 days), even if symptoms improve, to prevent bacterial resistance or recurrence. Stopping early can worsen the infection.
24. Can Cephalexin be stopped suddenly?
Don’t stop early unless advised by a doctor, as it may lead to incomplete treatment. There’s no withdrawal risk, but the infection could return.
25. Does Cephalexin affect blood sugar?
No, it doesn’t directly affect blood sugar. Any changes would be unrelated to the drug.
26. Can Cephalexin cause yeast infections?
Yes, by disrupting normal flora, it can increase the risk of vaginal yeast infections or oral thrush, especially in women or those with diabetes.
27. What should I avoid while taking Cephalexin?
Avoid skipping doses and unnecessary antibiotics to prevent resistance. No specific food or activity restrictions apply.
28. Can Cephalexin cause fatigue?
Fatigue isn’t a common side effect. If it occurs, it’s likely from the infection, not the drug.
29. Is Cephalexin safe for elderly patients?
Yes, but dose adjustments may be needed for reduced kidney function, common in older adults. Monitoring is key.
30. Does Cephalexin affect the liver?
Rarely, it may cause mild liver enzyme elevations, but significant liver damage is uncommon unless pre-existing liver disease exists.
31. Can Cephalexin be used in children?
Yes, it’s safe for children with weight-based dosing (25–100 mg/kg/day). It’s commonly used for ear or skin infections.
32. What’s the maximum dose of Cephalexin?
The maximum is 4 grams daily for adults, split into doses, though this is rare and reserved for severe infections.
33. Can Cephalexin cause dizziness?
Dizziness is rare and not a typical side effect. If it occurs, it might relate to dehydration or the infection.
34. How is Cephalexin different from other antibiotics?
Compared to penicillins, it’s broader-spectrum but less effective against some gram-negative bacteria than later cephalosporins. It’s oral and well-tolerated.
35. Can Cephalexin prevent infections?
It’s not typically used preventatively except in specific cases (e.g., endocarditis prophylaxis). It’s mainly for active infections.
36. Does Cephalexin affect cholesterol?
No, it has no impact on cholesterol levels.
37. Can Cephalexin be taken with other antibiotics?
Rarely, it’s combined with others for complex infections, but this is doctor-directed. Usually, it’s used alone.
38. What tests should I get while on Cephalexin?
For long-term or high-dose use, check kidney function and liver enzymes. Routine monitoring isn’t needed for short courses.
39. Can Cephalexin cause depression?
No, it doesn’t affect mood or the brain. Depression would be unrelated.
40. Is Cephalexin addictive?
No, it’s not addictive or habit-forming.
41. Can Cephalexin be crushed?
Capsules shouldn’t be crushed, but tablets can be if needed (check with a pharmacist). Liquid forms are available.
42. Does Cephalexin cause hair loss?
No, hair loss isn’t a side effect. Any loss would be from another cause.
43. Can Cephalexin be used for acne?
It’s not a first-line acne treatment but may be used for severe bacterial skin infections contributing to acne.
44. What’s the half-life of Cephalexin?
Its half-life is about 1 hour in healthy adults, longer with kidney impairment, requiring dose adjustments.
45. Can Cephalexin cause a rash?
Yes, a mild rash is possible, especially with sensitivity. A severe rash may signal an allergy—stop use and seek help.
46. Does Cephalexin affect exercise?
No direct effect, but if you’re unwell, exercise may feel harder. Side effects like diarrhea could also impact activity.
47. Can Cephalexin be taken with aspirin?
Yes, there’s no significant interaction. It’s safe to combine if needed.
48. Is Cephalexin expensive?
No, as a generic, it’s affordable, often costing $10–$20 for a course, depending on dose and region.
49. Can Cephalexin cause stomach pain?
Yes, mild stomach pain or nausea can occur, especially if taken on an empty stomach. Food may help.
50. How should Cephalexin be stored?
Store at room temperature (15–30°C or 59–86°F), away from moisture and heat. Keep liquid forms refrigerated if specified.