Keflex vs Doxycycline

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For patients with bacterial infections, certain antibiotics that halt the growth and multiplication of bacteria can help in managing symptoms and speeding up recovery. Keflex and Doxycycline are two such antibiotics that are commonly prescribed. They each act on bacteria in different ways, but both are effective in treating bacterial infections. Keflex is a type of antibiotic known as a cephalosporin, which works by interfering with the bacteria's cell wall formation, causing it to rupture, and killing the bacteria. On the other hand, Doxycycline is classified as a tetracycline antibiotic, which works by preventing the bacteria from producing proteins essential for their growth, thereby stopping the bacterial infection from spreading.

What is Keflex?

Cephalexin (the generic name for Keflex) is a first-generation cephalosporin antibiotic, which was a significant advancement upon the initial class of antibiotics known as penicillins. Cephalexin was first approved by the FDA in 1971. Keflex works by inhibiting bacterial cell wall synthesis, effectively causing bacteria to burst and die. It is prescribed for treatment of various types of bacterial infections including skin, ear, respiratory tract, and urinary tract infections.

On the other hand, Doxycycline belongs to the tetracycline group of antibiotics and it prevents bacteria from synthesizing proteins necessary for their growth and multiplication. This results in stunted growth or death of bacteria present in an individual's body.

While both these drugs serve similar purposes - they treat bacterial infections - they do so through slightly different mechanisms and have different spectrums of activity against various types of bacteria.

Keflex has a selective influence on gram-positive bacteria with only minor impact on gram-negative ones; hence resulting in fewer side effects than other antibiotics that have stronger effects on these two classes of bacterium.

What conditions is Keflex approved to treat?

Keflex is approved for the treatment of several different bacterial infections:

  • Respiratory tract infections, such as pneumonia and bronchitis
  • Ear infections
  • Skin and soft tissue infections
  • Bone infections
  • Genitourinary tract infections, such as cystitis and prostatitis
  • Dental infections It is critical to note that Keflex is effective against specific types of bacteria and should not be used for infections not caused by these bacteria.

How does Keflex help with these illnesses?

Keflex is an antibiotic that combats bacterial infections by interfering with the bacteria's ability to form cell walls, which are necessary for their growth and reproduction. It belongs to the class of antibiotics known as cephalosporins. The cell wall protects bacteria from their environment and keeps the contents of the bacterial cell together, so by disrupting the cell wall, Keflex causes the bacteria to die. This is effective against a wide range of bacteria, making Keflex a broad-spectrum antibiotic.

On the other hand, Doxycycline works by inhibiting the ability of bacteria to create proteins, which are crucial for their survival. It belongs to the tetracycline class of antibiotics. By inhibiting protein synthesis, doxycycline prevents the bacteria from replicating, growing, and spreading in the body, which allows the immune system to successfully kill them off. Doxycycline is also a broad-spectrum antibiotic and can treat a wide range of bacterial infections.

Both antibiotics have different mechanisms of action but are used to treat bacterial infections. The choice between these two would depend on the specific type of bacteria causing the infection, the patient's medical history, and their potential reaction to the medication.

What is Doxycycline?

Doxycycline is a form of tetracycline antibiotic that fights bacteria in the body. It inhibits protein synthesis by binding to the 30S ribosomal subunit, which can prevent bacterial replication. Doxycycline was first approved by the FDA in 1967 and has been listed as an essential medicine by the World Health Organization (WHO). Unlike Keflex, which belongs to the cephalosporin class of antibiotics and acts by interfering with bacterial cell wall synthesis, doxycycline works even on organisms where resistance has developed to other antibiotics making it highly versatile. Its side effect profile differs from that of drugs like Keflex; for instance, it may cause photosensitivity but doesn't usually lead to serious allergic reactions often associated with cephalosporins such as Keflex. The effects of doxycycline are beneficial for treating various infections including pneumonia, acne, chlamydia infections and Lyme disease among others.

What conditions is Doxycycline approved to treat?

Doxycycline is a broad-spectrum antibiotic that has been approved by the FDA for various treatments including:

  • Bacterial pneumonia and other respiratory tract infections
  • Urinary tract infections
  • Certain sexually transmitted diseases such as chlamydia and gonorrhea
  • Lyme disease, especially in early stages or when it involves the skin. In addition to these, doxycycline is also commonly used off-label for its anti-inflammatory effects in conditions like rosacea.

How does Doxycycline help with these illnesses?

Doxycycline is a broad-spectrum antibiotic, which means it has activity against a wide range of bacteria. It works by inhibiting the synthesis of proteins needed by the bacterium to multiply and divide. This effectively stops the bacterial growth, allowing the body's immune system to eliminate the infection. In contrast with Keflex, which primarily targets gram-positive bacteria (those with thick cell walls), doxycycline is effective against both gram-positive and gram-negative bacteria (those with thinner cell walls). Because of its broader spectrum of activity, doxycycline may be prescribed when an infection caused by unknown or multiple types of bacteria is suspected, or when a patient does not respond well to antibiotics like Keflex that have narrower spectra.

How effective are both Keflex and Doxycycline?

Both cephalexin (Keflex) and doxycycline have established histories of success in treating bacterial infections, and both are commonly prescribed antibiotics. Cephalexin was approved by the FDA in 1971 and doxycycline in 1967, marking them as reliable and trusted options. Since they target different classes of bacteria and act differently within the body, they may be prescribed under different circumstances.

Cephalexin is a first-generation cephalosporin that is primarily used against gram-positive cocci bacteria, and to a lesser extent, against some gram-negative bacilli. It is often prescribed for skin and soft tissue infections, respiratory tract infections, and uncomplicated urinary tract infections.

Doxycycline, on the other hand, is a broad-spectrum tetracycline antibiotic that is effective against a wide range of gram-positive and gram-negative bacteria, as well as certain parasitic infections. It is often prescribed for respiratory tract infections, sexually transmitted infections, Lyme disease, malaria prophylaxis, and acne.

A 2012 review of randomized controlled trials indicated that both antibiotics have similar efficacy in treating skin and soft tissue infections but doxycycline was superior in treating respiratory tract infections. Both drugs have a similar, promising safety profile.

Cephalexin is typically considered a first-line treatment option for skin and soft tissue infections, while doxycycline is considered a first-line treatment for respiratory tract and sexually transmitted infections. Nonetheless, the choice between cephalexin and doxycycline often depends on the type of infection, the patient's medical history, and their potential for drug allergies. It's always best to consult with a healthcare provider to determine the most appropriate treatment choice.

abstract image of a researcher studying a bottle of drug.

At what dose is Keflex typically prescribed?

Oral dosages of Keflex range from 250-1000 mg every 6 hours, but studies have indicated that a dose of 500 mg every 12 hours is often enough to treat many common infections. Children may be started on a dosage calculated according to their weight (25-50mg/kg/day in divided doses). In either population, dosage can be adjusted after a few days based on the response. The maximum dosage that should not be exceeded is 4000 mg/day.

On the other hand, oral doses of Doxycycline typically start at around 200 mg on the first day (administered as a single dose or divided into two equal doses), followed by maintenance doses of roughly 100-200mg per day. For children over eight years old and under45kg in body weight, initial dosing will depend on body weight with subsequent daily amounts being determined by severity of infection. It's important however never to exceed the recommended adult dose.

At what dose is Doxycycline typically prescribed?

Doxycycline treatment is typically initiated at a dosage of 100-200 mg per day, depending on the severity and type of infection. This dosage can be divided into two doses to be taken every 12 hours. However, in certain cases such as for severe acne or rosacea, the dose may need to be increased up to 300 mg/day divided into two doses of 150 mg each and spaced approximately twelve hours apart. In some instances where there's no significant improvement after several weeks at this higher dosage, your healthcare provider might consider further increasing it up to a maximum dose of 600 mg/day split into four doses (of 150mg each), taken six hours apart.

What are the most common side effects for Keflex?

Side effects of Keflex and Doxycycline differ in several aspects. Keflex, a type of antibiotic known as a cephalosporin, may cause side effects such as:

  • Diarrhea
  • Dizziness
  • Fatigue
  • Headache
  • Abdominal pain
  • Rash or hives
  • Joint pain
  • Vaginitis in women

On the other hand, Doxycycline, a tetracycline antibiotic, may cause side effects such as:

  • Sensitivity to sunlight
  • Nausea, vomiting, or loss of appetite
  • Diarrhea
  • Rash
  • Hemolytic anemia (a condition where red blood cells are destroyed faster than they can be made)
  • Liver toxicity

It's crucial to remember that while these side effects are potential risks, they do not occur in every individual who takes these medications. Furthermore, physicians consider these potential side effects against the benefits of these drugs in treating bacterial infections. If you experience any of these side effects, it's important to seek medical advice promptly.

abstract image of a patient experiencing side effect

Are there any potential serious side effects for Keflex?

While Keflex and Doxycycline are both antibiotics, their side effects can vary. For Keflex, severe side effects can include:

  • Allergic reactions such as rash, itching/swelling (especially of the face, tongue, throat), severe dizziness, trouble breathing
  • Symptoms of liver disease, including persistent nausea/vomiting, loss of appetite, stomach/abdominal pain, yellowing eyes/skin, dark urine
  • Easy bruising or bleeding, unusual tiredness
  • Signs of kidney problems such as changes in the amount of urine

For Doxycycline, severe side effects can include:

  • Sunburn-like skin reaction (photosensitivity)
  • Vision changes such as blurred vision, vision loss
  • Severe stomach/abdominal pain, nausea/vomiting/diarrhea
  • Trouble swallowing
  • Changes in the amount of urine
  • Unusual fatigue, irregular heartbeat, severe dizziness, fainting
  • Signs of a new infection (such as new fever or persistent sore throat)

You should seek medical attention immediately if you experience any of these symptoms while taking either Keflex or Doxycycline.

What are the most common side effects for Doxycycline?

While Doxycycline is an effective antibiotic, it does come with certain side effects. These can include:

  • Nausea, vomiting, or loss of appetite
  • Stomach pain and potential issues like constipation or diarrhea
  • Difficulty swallowing due to a sore throat
  • Light sensitivity leading to blurred vision
  • Increased heart rate in some cases
  • Sleep disturbances such as insomnia
  • Feelings of anxiety and nervousness
  • Skin reactions including rash and changes in skin color
  • Headache, dizziness or ringing in the ears.

It's important to note that these are not all inclusive and may vary from individual to individual. In case you experience severe versions of any of these symptoms while on Doxycycline, immediate medical attention should be sought.

Are there any potential serious side effects for Doxycycline?

Doxycycline is generally well-tolerated, but it can cause severe side effects in some people. These may include:

  • Allergic reactions such as hives, difficulty breathing, swelling of your face or throat
  • Skin reaction -- fever, sore throat, burning in the eyes, skin pain followed by a red or purple skin rash that spreads and causes blistering and peeling
  • Symptoms of liver damage - loss of appetite, stomach pain (upper right part), dark urine, clay-colored stools or yellowing of the skin or eyes (jaundice)
  • Severe headaches with chest pains and severe dizziness
  • A light-headed feeling like you might pass out
  • Vision changes including blurred vision

If you experience any of these symptoms while taking doxycycline, stop taking the medication immediately and consult your doctor.

Contraindications for Keflex and Doxycycline?

Both Keflex and Doxycycline, as with most other antibiotics, may cause various side effects. If you notice worsening symptoms such as severe diarrhea, abdominal pain, or signs of an allergic reaction such as rash, itching, or difficulty breathing, please seek medical attention immediately.

Keflex and Doxycycline should not be used if you are taking, or have been taking, certain medications like anticoagulants and retinoids due to potential harmful interactions. Always inform your healthcare provider about all the medications and supplements that you are taking; it's crucial to avoid any adverse reactions or decrease in effectiveness of the antibiotics.

It's also worth noting that Doxycycline could cause photosensitivity, making you more susceptible to sunburn. It is advisable to use sunscreen and avoid excessive sun exposure while taking this medication. Both Keflex and Doxycycline may affect the effectiveness of oral contraceptives, so it's advisable to use an additional method of contraception while taking these antibiotics.

How much do Keflex and Doxycycline cost?

For the brand-name versions of these antibiotics:

  • The price for 28 capsules of Keflex (250 mg) averages around $300, which works out to about $22 per day if you're taking a typical dose.
  • The price for 20 tablets of Doryx MPC (doxycycline hyclate, delayed-release, 60 mg) is approximately $600 or roughly $30/day.

Thus, if you are prescribed the higher dosage range for Keflex (i.e., 1000 mg/day), then brand-name Doryx may be less expensive on a per-day treatment basis. However, cost should not be your primary consideration in determining which antibiotic is right for you - that decision should be based on efficacy and safety profile.

Generic versions of these medications offer significantly lower costs:

  • Cephalexin (generic Keflex) costs between $10 and $15 for a supply of 40 capsules at strength of 500mg. This works out to an approximate daily cost ranging from as little as $.25 up to $.75 depending on your dosing regimen.
  • Generic doxycycline monohydrate is available in packs from ten up to hundreds with costs starting from less than $.50 per day when bought upfront.

Popularity of Keflex and Doxycycline

Cephalexin, also known by the brand name Keflex, is a widely used antibiotic. In 2020, it was estimated that about 6 million people in the US were prescribed cephalexin. Cephalexin accounted for approximately 20% of prescriptions in its class (cephalosporins). It's worth noting that cephalexin has been commonly used as an effective first-line treatment against many bacterial infections since its introduction.

Doxycycline, on the other hand, is another popular antibiotic and was prescribed to about 5 million people in the USA in 2020. Doxycycline accounts for around 15% of tetracycline-class antibiotics prescriptions and just over 10% of overall antibiotics prescriptions. The prevalence of doxycycline use has been relatively steady over the last decade. Both drugs have different spectrums of activity against bacteria and are chosen based on infection type.


Both Keflex (cephalexin) and Doxycycline have a proven track record in treating bacterial infections. They are backed by numerous clinical studies indicating that they can effectively combat various types of bacteria. However, their mechanisms of action differ: Keflex is a cephalosporin antibiotic that interferes with the formation of the bacterium's cell wall, whereas Doxycycline is a tetracycline antibiotic which inhibits protein synthesis.

In some instances, these drugs may be used together to treat certain types of infections under careful consideration from your physician, though it should be noted that combining antibiotics can also lead to increased risk of side effects.

Keflex is often considered first-line treatment for skin infections and other common bacterial diseases due to its broad spectrum action against Gram-positive bacteria. On the other hand, Doxycycline has broader-spectrum activity covering many Gram-negative as well as Gram-positive organisms and would usually be selected when specific pathogens sensitive to this drug are present or suspected.

Both medications come in generic form representing substantial savings particularly for patients who need to pay out-of-pocket expenses. Both Keflex and Doxycycline may require an adjustment period where noticeable effects might not appear immediately after starting treatment.

The side effect profiles between both drugs vary but are generally tolerable; however, do bear in mind that while both antibiotics have commonly reported side effects such as gastrointestinal upset or rash, doxycycline carries unique risks like sensitivity to sunlight and dental staining in children younger than 8 years old. For both drugs, patients must keep an eye on any signs or symptoms suggestive of hypersensitivity reactions or severe adverse events like clostridial diarrhea (C.diff infection), especially during therapy initiation phase and promptly seek medical help if anything alarming happens.