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Flagyl vs Keflex
Introduction
For patients with bacterial infections, certain drugs that inhibit the growth or kill bacteria can help in controlling and managing symptoms. Flagyl (metronidazole) and Keflex (cephalexin) are two such antibiotics that are often prescribed for treating various types of bacterial infections. They each work differently but both have bactericidal effects on targeted organisms.
Flagyl is an antibiotic effective against anaerobic bacteria and certain parasites by inhibiting protein synthesis and causing cell death. It's primarily used to treat gastrointestinal infections caused by Giardia lamblia or Entamoeba histolytica, as well as vaginal infections caused by Trichomonas.
On the other hand, Keflex belongs to a class of antibiotics known as cephalosporins which block bacterial cell wall synthesis leading to cell rupture and death. It works against a broad range of gram-positive bacteria making it useful in skin or soft tissue infections among others.
Flagyl vs Keflex Side By Side
| Attribute | Flagyl | Keflex |
|---|---|---|
| Brand Name | Flagyl | Keflex |
| Contraindications | Allergy to metronidazole, alcohol consumption during treatment and for at least 48 hours after completion of treatment. | Allergy to cephalosporins. |
| Cost | Brand name: around $50 for 14 tablets of 500 mg. Generic: starts as low as $0.10 up to around $2 per day depending on dosage and pack size. | Brand name: around $60 for 20 capsules of 500 mg. Generic: daily rates starting at just above negligible amounts but potentially reaching over a dollar per day. |
| Generic Name | Metronidazole | Cephalexin |
| Most Serious Side Effect | Neurological symptoms such as seizures or numbness/tingling in the hands or feet, signs of a severe allergic reaction, unexplained mood changes, confusion, hallucinations, liver problems. | Allergic reactions including hives; difficulty breathing; swelling of your face, lips, tongue, or throat, severe stomach pain or diarrhea that is watery or bloody, unusual tiredness or weakness, easy bruising or bleeding, yellowing of the skin and eyes (jaundice), dark-colored urine and light-colored stools, a seizure, confusion and agitation, rapid heart rate. |
| Severe Drug Interactions | Not explicitly mentioned in the text, but typically includes alcohol and drugs that may cause disulfiram-like reactions. | Not explicitly mentioned in the text, but typically includes other antibiotics that may alter gut flora significantly. |
| Typical Dose | 250-750 mg three times a day for adults. Pediatric dose starts at 30 to 40 mg/kg/day divided into four doses. | 250 mg every 6 hours, can be increased to 500 mg every 12 hours. In severe infections, up to 4 g per day divided into four doses. |
What is Flagyl?
Metronidazole (the generic name for Flagyl) was one of the first antibiotics in the nitroimidazole class to be widely used, which marked a significant advancement from earlier classes of antimicrobial agents. Metronidazole was approved by the FDA in 1963. Flagyl is effective against anaerobic bacteria and certain parasites by interfering with their DNA synthesis, effectively disrupting their growth and survival. It is commonly prescribed for infections caused by anaerobic bacteria such as Bacteroides species, Clostridium spp., Fusobacterium spp., Peptostreptococcus spp., or Prevotella bivia. Metronidazole has strong activity against susceptible organisms but does not affect aerobic bacteria or fungi, which results in it having fewer side effects due to superinfection than other antibiotics that have broader antimicrobial spectra.
Cephalexin (the generic name for Keflex), on the other hand, belongs to a different class of antibiotics known as cephalosporins and is effective against both aerobic Gram-positive and some Gram-negative bacteria. Cephalexin disrupts bacterial cell wall synthesis leading to its death - this mechanism makes it useful for treating many types of infection including skin infections, bone infections, ear infections etc.
What conditions is Flagyl approved to treat?
Flagyl is approved for the treatment of different types of infections:
- Various anaerobic bacterial infections, including those associated with intra-abdominal disorders, skin and skin structure, lower respiratory tract, endocardium (lining of the heart), bones and joints
- Protozoal infections such as amebiasis and trichomoniasis
- In combination with other antibiotics to treat Helicobacter pylori that causes stomach or intestinal ulcers.
Similarly, Keflex is also used to treat a range of bacterial infections:
- Respiratory tract infections caused by Streptococcus pneumoniae and Streptococcus pyogenes.
- Otitis media (ear infection) due to Streptococcus pneumoniae or Haemophilus influenzae.
- Skin and soft tissue structures infected by Staphylococcus aureus or Streptococcus pyogenes.
- Bone Infections caused by Staphylococcus aureus or Proteus mirabilis.
How does Flagyl help with these illnesses?
Flagyl, also known as metronidazole, works to manage bacterial and parasitic infections by inhibiting nucleic acid synthesis in these organisms. It does this by infiltrating their cells and disrupting the function of their DNA, which ultimately leads to cell death. This action is specific to anaerobic bacteria and certain parasites, which makes Flagyl a potent weapon against these types of infections. On the other hand, Keflex or cephalexin is a broad spectrum antibiotic that hinders bacterial growth by interfering with the formation of the bacterium's cell wall. This causes instability and eventual rupture of the bacterial cells leading to its destruction. Unlike Flagyl which targets only anaerobes and some parasites, Keflex can be used against a wider range of bacteria including staphylococcus aureus, streptococcus pneumoniae among others.
What is Keflex?
Keflex is a brand name for cephalexin, which is a first-generation cephalosporin antibiotic. It works by interfering with the bacteria's cell wall formation, causing the wall to rupture and ultimately leading to bacterial death. Cephalexin was first approved by the FDA in 1971. Unlike metronidazole (Flagyl), an antibiotic that primarily targets anaerobic bacteria and protozoa, Keflex has broad-spectrum activity against both Gram-positive and some Gram-negative bacteria making it useful in treating a wider range of infections including those of the skin, bone, respiratory tract as well as urinary tract infections. In terms of side effects, cephalexin does not have many of Flagyl's neurological side effects such as headache or dizziness but can instead cause gastrointestinal disturbances like diarrhea or nausea more frequently than Flagyl. The versatility and safety profile make Keflex potentially beneficial especially for patients who cannot tolerate other types of antibiotics such as metronidazole.
What conditions is Keflex approved to treat?
Keflex is a first-generation cephalosporin that has been approved for the treatment of various bacterial infections such as:
- Upper respiratory tract infections
- Ear infections (otitis media)
- Skin and soft tissue infections
- Bone infections
- Genitourinary tract Infections
How does Keflex help with these illnesses?
Keflex, also known as Cephalexin, is an antibiotic that plays a crucial role in combating bacterial infections within the body. It achieves this by inhibiting the formation of cell walls in bacteria, thereby leading to their destruction and eradication from the body. Keflex primarily targets Gram-positive bacteria such as Streptococcus pneumoniae and Staphylococcus aureus but can also work against some Gram-negative bacteria. This makes it quite versatile for treating various types of infections including skin, ear, bone and respiratory tract infections. Unlike Flagyl (metronidazole), which is mainly used against anaerobic microorganisms and protozoa, Keflex does not have any significant activity against these types of pathogens. Therefore, physicians might prescribe Keflex when a patient's symptoms suggest they are dealing with a type of infection that it is particularly effective at eliminating.
How effective are both Flagyl and Keflex?
Both metronidazole (Flagyl) and cephalexin (Keflex) have well-established histories of success in treating bacterial infections, though they were approved by the FDA several decades apart. Since they act on different types of bacteria, they may be prescribed under differing circumstances. The effectiveness of Flagyl and Keflex in combating bacterial infection was directly studied in many clinical trials; both antibiotics exhibited similar efficacy in managing symptoms as well as safety profiles.
A 2004 review reported that metronidazole is highly effective against anaerobic bacteria and certain parasites, which makes it a drug of choice for conditions such as dental or intra-abdominal infections, amoebiasis and trichomoniasis. It's generally well-tolerated with common side effects being nausea and metallic taste.
Cephalexin on the other hand is a first-generation cephalosporin that's very effective against gram-positive bacteria including Staphylococcus aureus strains, making it an ideal choice for skin or soft tissue infections among others. However, its use often leads to resistance development hence should be judiciously used.
In summary while both drugs are effective antibiotics their usage depends largely on the type of infecting organism(s). As always antibiotic stewardship programs recommend culture-guided therapy whenever possible to prevent unnecessary exposure leading to resistance development.
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At what dose is Flagyl typically prescribed?
Oral dosages of Flagyl (metronidazole) typically range from 250-750 mg, three times a day for adults. However, studies suggest that a dosage of 500 mg three times daily is generally sufficient for treating most bacterial infections in adults. In pediatric patients, the dose can begin as low as 30 to 40 mg/kg/day divided into four doses. If there's no response after a few days, your doctor may adjust the dosage accordingly. The maximum recommended adult dose should not exceed 4 g per day.
At what dose is Keflex typically prescribed?
Keflex treatment typically begins with a dosage of 250 mg every 6 hours. The dose can then be increased to 500 mg taken every 12 hours, divided into two doses, spaced approximately evenly apart. In severe infections, the maximum dose is up to 4 g per day divided into four doses of roughly equal size and spaced approximately six hours apart. This may be tested if there is no response to initial treatment after several days. As always, follow your doctor's instructions when taking any medication.
What are the most common side effects for Flagyl?
The following are some potential side effects of Flagyl:
- Nausea, vomiting, loss of appetite or metallic taste
- Diarrhea, constipation or abdominal cramping
- Dry mouth and a furry tongue
- Dizziness or headache
- Sleep disorders such as insomnia and unusual dreams
- Darkened urine due to metabolites of the drug
On the other hand, Keflex may cause:
- Diarrhea (may be severe)
- Nausea and vomiting
- Abdominal pain
- Rash, hives or itching -Swelling under your skin typically around your lips and eyes (angioedema) -Difficulty breathing
These lists are not exhaustive; always consult with a healthcare professional for personalized advice.
Are there any potential serious side effects for Flagyl?
While Flagyl and Keflex are both antibiotics, they have different side effect profiles. For Flagyl (metronidazole), serious side effects can include:
- Neurological symptoms such as seizures or numbness/tingling in the hands or feet
- Signs of a severe allergic reaction like rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing
- Unexplained mood changes, confusion, hallucinations
- Liver problems marked by stomach pain on the upper right side, persistent nausea/vomiting and dark urine
On the other hand for Keflex (cephalexin), watch out for:
- Allergic reactions including hives; difficulty breathing; swelling of your face, lips, tongue or throat
- Symptoms of kidney issues such as little or no urination; painful or difficult urination; swelling in your feet or ankles etc.
- Severe skin reaction - fever/sore throat/burning eyes/skin pain/red/purple skin rash with blistering/peeling
If any unusual symptoms occur while taking either drug please consult a healthcare professional immediately.
What are the most common side effects for Keflex?
Common side effects of Keflex include:
- Digestive issues like nausea, vomiting, stomach pain and diarrhea
- Dizziness or tiredness
- Headache
- Joint or muscle pain
- Genital itching or discharge It's also worth mentioning that some people may experience an allergic reaction to Keflex, which can cause a rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, and trouble breathing. As always when starting a new medication regimen, if you notice any unusual symptoms it is important to consult your healthcare provider immediately.
Are there any potential serious side effects for Keflex?
While Keflex is generally safe for most people, it can lead to serious side effects in rare cases. These include:
- Signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat
- Severe stomach pain or diarrhea that is watery or bloody (even if this occurs months after your last dose)
- Unusual tiredness or weakness, easy bruising or bleeding
- Yellowing of the skin and eyes (jaundice)
- Dark-colored urine and light-colored stools
- A seizure (convulsions);
- Confusion and agitation;
- Rapid heart rate
If you notice any such symptoms while taking Keflex, stop its usage immediately and seek urgent medical attention.
Contraindications for Flagyl and Keflex?
Both Flagyl (metronidazole) and Keflex (cephalexin), like most antibiotics, can cause side effects such as nausea, diarrhea, vomiting or skin rash. If you notice a significant increase in these symptoms while taking either medication, seek immediate medical attention.
Neither Flagyl nor Keflex should be taken if you are allergic to metronidazole or cephalosporins respectively. Always inform your doctor of any allergies you may have to medications; an allergic reaction will often lead to symptoms like itching, swelling of the face/tongue/throat, severe dizziness and difficulty breathing.
Furthermore, it's important to note that alcohol must be completely avoided during treatment with Flagyl and for at least 48 hours after completion of treatment due to possible reactions such as flushing, headache and nausea. While this is not a concern with Keflex use per se, alcohol consumption can still impair immune function making recovery from infection more difficult.
Always disclose your complete health history and current medication regimen—including over-the-counter drugs—to your healthcare provider prior starting new treatments with either Flagyl or Keflex.
How much do Flagyl and Keflex cost?
For the brand name versions of these antibiotics:
- The price for 14 tablets of Flagyl (500 mg) averages around $50, which works out to about $3.57/day.
- Conversely, the cost for 20 capsules of Keflex (500 mg) is approximately $60, translating to roughly $3/day.
This means that if you are in a higher dosage range for Flagyl (i.e., 2000 mg/day), then the brand-name Keflex will be less expensive on a per-day treatment basis. As always, cost should not be your primary consideration when determining which drug best suits your needs.
Turning now to generic version costs:
-
Metronidazole, the generic form of Flagyl with doses available from 250mg up to 750mg, comes in packs ranging from 20 up to hundreds of tablets. Daily costs can start as low as $0.10 and reach up to around $2 depending on pack size and dosage requirements.
-
Cephalexin, known commonly by its brand name Keflex but also available generically in dosages between 250mg and 1000mg has similar pricing structures - daily rates starting at just above negligible amounts ($0.05 per day or so if buying larger quantities upfront) but potentially reaching over a dollar per day depending upon individual circumstances such as location or insurance coverage status.
Popularity of Flagyl and Keflex
Metronidazole, also known by the brand name Flagyl, was estimated to have been prescribed to about 8.2 million people in the US in 2017. It is an antibiotic and antiprotozoal medication used primarily to treat bacterial infections caused by anaerobic bacteria and certain parasites. Metronidazole accounted for a significant portion of antibiotics prescriptions in the US, especially for conditions like bacterial vaginosis and trichomoniasis.
Cephalexin, commonly referred to as Keflex among other brand names, was prescribed to approximately 6 million individuals in the USA during 2020. This first-generation cephalosporin antibiotic accounts for a substantial proportion of overall cephalosporins prescriptions and is frequently used against gram-positive cocci infections such as skin and soft tissue infections or upper respiratory tract infections. The prescription prevalence of cephalexin has remained relatively steady over recent years.
Conclusion
Both Flagyl (metronidazole) and Keflex (cephalexin) are frequently used in the treatment of various bacterial infections. They are backed by numerous clinical studies and meta-analyses indicating that they are more effective than placebo treatments. The drugs should not be combined without careful consideration by a physician as they treat different types of bacteria. Due to their different mechanisms of action, with Flagyl being primarily active against anaerobic bacteria and certain parasites, and Keflex being effective against a wide range of Gram-positive and some Gram-negative bacteria, they tend to be prescribed under different circumstances.
Flagyl is considered a first-line treatment option for infections like bacterial vaginosis or parasitic infections like giardiasis, whereas Keflex would usually be considered as a first-line treatment for skin infections or certain respiratory tract infections.
Both drugs are available in generic form, which represents significant cost savings especially for patients who must pay out of pocket. Both Flagyl and Keflex may require an adjustment period, meaning that effects may not be noticeable right away.
The side effect profile is similar between the two drugs, both being generally well-tolerated, but with Flagyl having more potential for gastrointestinal side effects and a metallic taste, and Keflex may cause more allergic reactions. For both drugs, patients must closely monitor their symptoms, especially when starting treatment, and should seek medical help immediately if they notice their infection worsening or have severe side effects.
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Refrences
- Earl, P., Sisson, P. R., & Ingham, H. R. (1989). Twelve-hourly dosage schedule for oral and intravenous metronidazole. Journal of Antimicrobial Chemotherapy. Oxford University Press (OUP).http://doi.org/10.1093/jac/23.4.619
- Leitsch, D. (2017, November 23). A review on metronidazole: an old warhorse in antimicrobial chemotherapy. Parasitology. Cambridge University Press (CUP).http://doi.org/10.1017/s0031182017002025