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Doxycycline vs. Keflex: What's the difference?
- Doxycycline and Keflex (cephalexin) are antibiotics used to treat many different types of bacterial infections.
- Brand names for doxycycline include Vibramycin, Oracea, Adoxa, Atridox, Acticlate, Acticlate Cap, Doryx, Doxteric, Doxy, and Monodox.
- Keflex and Daxbia are brand names for cephalexin.
- Doxycycline and Keflex are different types of antibiotics. Doxycycline is a tetracycline antibiotic and Keflex is a cephalosporin antibiotic.
- Side effects of doxycycline and Keflex that are similar include diarrhea or loose stools, nausea, abdominal pain, or vomiting.
- Side effects of doxycycline that are different from Keflex include tooth discoloration if used in persons below 8 years of age, and exaggerated sunburn.
- Side effects of Keflex that are different from doxycycline include headaches, dizziness, skin rash, fever, abnormal liver tests, and vaginitis.
What are doxycycline and Keflex?
Doxycycline is a tetracycline class antibiotic used to treat a variety of infections, such as respiratory tract infections due to Hemophilus influenzae, Streptococcus pneumoniae, or Mycoplasma pneumoniae. Doxycycline also is used to treat nongonococcal urethritis (due to Ureaplasma), typhus, cholera, chancroid, brucellosis, Rocky Mountain spotted fever, anthrax, syphilis, acne, and periodontal disease.
Keflex (cephalexin) is a cephalosporin antibiotic, which is similar to penicillin in action and side effects. Bacteria susceptible to Keflex include Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus influenzae, E. coli, and others. Keflex is used to treat infections such as middle ear infections (otitis media), tonsillitis, throat infections, laryngitis, bronchitis, pneumonia, urinary tract infections (UTIs), skin infections, and bone infections.
What are the side effects of doxycycline and Keflex?
Doxycycline is generally well tolerated. The most common side effects are:
- Diarrhea or loose stools
- Abdominal pain
Tetracyclines, such as doxycycline, may cause tooth discoloration if used in persons below 8 years of age. Exaggerated sunburn can occur with tetracyclines; therefore, minimize sunlight exposure during treatment.
The most common side effects of Keflex are:
- Abdominal pain
- Skin rash
- Abnormal liver tests
Individuals who are allergic to penicillin may also be allergic to Keflex. Serious but rare reactions include seizures, severe allergic reactions (anaphylaxis), and low platelet or red blood cell count.
Keflex, like almost all antibiotics, may cause mild or severe cases of pseudomembranous colitis, a mild to severe inflammation of the colon. Antibiotics, including Keflex alter the types of bacteria in the colon and permit overgrowth of a bacterium called Clostridium difficile. Studies indicate that toxins produced by Clostridium difficile are a primary cause of pseudomembranous colitis.
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What is the dosage of doxycycline vs. Keflex?
- The absorption of doxycycline is not markedly affected by food and, therefore, it can be taken with meals.
- For most infections, doxycycline is taken once or twice daily for 7 to 14 days.
- For adult infections, the usual dose of oral doxycycline is 200 mg on the first day of treatment (100 mg every 12 hours) followed by a dose of 100 to 200 mg/day as a single dose or divided and administered twice daily.
- The dose of Keflex for adults is 1 to 4 grams in divided doses.
- The usual adult dose is 250 mg every 6 hours.
- Some infections may be treated with 500 mg every 12 hours.
- Children are treated with 25 to 100 mg/kg/day in divided doses.
- The dosing interval may be every 6 or 12 hours depending on the type and seriousness of the infection.
What drugs interact with doxycycline and Keflex?
- Do not take doxycycline at the same time as aluminum-, magnesium-, or calcium-based antacids such as Mylanta, Maalox, Tums, or Rolaids because, like food, these medications bind doxycycline in the intestine and prevent its absorption. Similarly, doxycycline should not be taken with minerals (such as calcium or iron) or with bismuth subsalicylate (Pepto Bismol).
- Doxycycline may enhance the activity of warfarin (Jantoven, Coumadin) and cause excessive "thinning" of the blood leading to exaggerated bleeding, necessitating a reduction in the dose of warfarin.
- Phenytoin (Dilantin), carbamazepine (Tegretol), and barbiturates (such as phenobarbital) may enhance the metabolism (destruction) of doxycycline, thus making it less effective.
- Doxycycline may interfere with the action of penicillins and should not be combined with penicillins.
- Doxycycline may also reduce the effectiveness of oral contraceptives.
- Combining tetracycline and methoxyflurane (Penthrane) may reduce kidney function.
- Keflex may reduce the effect of BCG and typhoid vaccines. Keflex should not be combined with BCG or typhoid vaccine unless there are no other options.
Are doxycycline and Keflex safe to use while pregnant or breastfeeding?
- Tetracycline antibiotics, such as doxycycline, can have toxic effects on development of bone in the fetus. Therefore, tetracyclines are not recommended during pregnancy unless there is no other appropriate antibiotic.
- Doxycycline is secreted into breast milk but the extent of absorption by the breastfed infant is not known. Since tetracyclines can cause toxic effects on bone, the use of tetracyclines in nursing mothers is of concern. The doctor must decide whether to recommend that a nursing mother discontinue nursing during treatment with tetracyclines or change to a different antibiotic.
- Keflex is excreted in breast milk. Keflex should be used with caution or stopped when breastfeeding.
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Related Disease Conditions
Upper Respiratory Infection (URTI)
An upper respiratory infection is a contagious infection of the structures of the upper respiratory tract, which includes the sinuses, nasal passages, pharynx, and larynx. Common causes of an upper respiratory infection include bacteria and viruses such as rhinoviruses, group A streptococci, influenza, respiratory syncytial, whooping cough, diphtheria, and Epstein-Barr. Examples of symptoms of upper respiratory infection include sneezing, sore throat, cough, fever, and nasal congestion. Treatment of upper respiratory infections are based upon the cause. Generally, viral infections are treated symptomatically with over-the-counter (OTC) medication and home remedies.
Inner Ear Infection (Symptoms, Signs, Treatments, Home Remedies)
An inner ear infection or otitis interna is caused by viruses or bacteria and can occur in both adults and children. An inner ear infection can cause symptoms and signs, for example, a severe ear, dizziness, vertigo, nausea and vomiting, and vertigo. An inner ear infection also may cause inflammation of the inner ear or labyrinthitis. Inner ear infections are not contagious; however, the bacteria and viruses that cause the infection can be transmitted to other people. Good hygiene practices will help decrease the chances of the infection spreading to others. Inner ear infection symptoms and signs like ear pain and nausea may be relieved with home remedies or over the counter (OTC) medication. Some inner ear infections will need to be treated and cured with antibiotics or prescription pain or antinausea medication.
Laryngitis is an inflammation of the voice box (vocal cords). The most common cause of acute laryngitis is infection, which inflames the vocal cords. Symptoms may vary from degree of laryngitis and age of the person (laryngitis in infants and children is more commonly caused by croup). Common symptoms include a "barky" cough, a hoarse cough, fever, cold, runny nose, dry cough, and loss of voice. Chronic laryngitis generally lasts more than three weeks. Causes other than infection include smoking, excess coughing, GERD, and more. Treatment depends on the cause of laryngitis.
Urinary Tract Infection (UTI)
A urinary tract infection (UTI) is an infection of the bladder, kidneys, ureters, or urethra. E. coli, a type of bacteria that lives in the bowel and near the anus, causes most UTIs. UTI symptoms include pain, abdominal pain, mild fever, urinary urgency, and frequency. Treatment involves a course of antibiotics.
Staph (Staphylococcus) Infection
Staphylococcus or staph is a group of bacteria that can cause a multitude of diseases. Staph infections can cause illness directly by infection or indirectly by the toxins they produce. Symptoms and signs of a staph infection include redness, swelling, pain, and drainage of pus. Minor skin infections are treated with an antibiotic ointment, while more serious infections are treated with intravenous antibiotics.
Middle Ear Infection (Otitis Media)
Middle ear infection (otitis media) is inflammation of the middle ear. There are two forms of this type of ear infection, acute and chronic. Acute otitis media is generally short in duration, and chronic otitis media generally lasts several weeks. Babies, toddlers, and children with a middle ear infection may be irritable, pull and tug at their ears, and experience numerous other symptoms and signs. Treatment depends upon the type of ear infection.
Is Strep Throat Contagious?
Strep throat is caused by group A streptococcus bacteria. Incubation period for strep throat is 1-5 days after exposure. If strep throat is treated with antibiotics, it is no longer contagious after 24 hours; if it is not treated with antibiotics, it is contagious for 2-3 weeks. Symptoms include fever, sore throat, tonsillitis, white spots or patches on the tonsils, and nausea and vomiting. Diagnosis of strep throat is performed through a rapid strep test.
Is Laryngitis Contagious?
Laryngitis is inflammation and swelling of the voice box (larynx). Causes of laryngitis are viral, bacterial, fungal, strenuous singing or talking, chemical irritants, and other underlying medical conditions. Symptoms of laryngitis are hoarseness, a weak or loss of voice, sore throat, dry throat, a tickling sensation in the back of the throat, or irritated or raw throat. Treatment of laryngitis depends upon the cause.
Bronchitis is inflammation of the airways in the lung. Acute bronchitis is short in duration (10-20 days) in comparison with chronic bronchitis, which lasts for months to years. Causes of acute bronchitis include viruses and bacteria, which means it can be contagious. Acute bronchitis caused by environmental factors such as pollution or cigarette smoke is not contagious. Common symptoms for acute bronchitis include nasal congestion, cough, headache, sore throat, muscle aches, and fatigue. Acute bronchitis in children also my include runny nose, fever, and chest pain. Treatment for acute bronchitis are OTC pain relievers, cough suppressants (although not recommended in children), and rest. Infrequently antibiotics may be prescribed to treat acute bronchitis.
Strep throat is a bacterial infection of the throat. Signs and symptoms of strep throat include headache, nausea, vomiting, sore throat, and fever. Strep throat symptoms in infants and children are different than in adults. Strep throat is contagious and is generally passed from person-to-person. Treatment for strep throat symptoms include home remedies and OTC medication; however, the only cure for strep throat are antibiotics.
Group A streptococcal infections are caused by group A Streptococcus, a bacteria that causes a variety of health problems, including strep throat, impetigo, cellulitis, erysipelas, and scarlet fever. There are more than 10 million group A strep infections each year.
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Urinary Tract Infections in Children
Urinary tract infections (UTIs) are very common in children. Symptoms and signs include fever and abdominal pain. Associated symptoms and signs include flank pain, vomiting, and blood in the urine. Treatment for a UTI involves antibiotic therapy.
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