Doxycycline vs. Tetracycline

• Doxycycline and tetracycline are antibiotics used for many different types of infections, including respiratory tract infections due to Hemophilus influenzae, Streptococcus pneumoniae, or Mycoplasma pneumoniae.
• Brand names for doxycycline include Vibramycin, Oracea, Adoxa, Atridox, Acticlate, Acticlate Cap, Doryx, Doxteric, and Doxy. Tetracycline is only available in generic form. Sumycin is a discontinued brand of tetracycline.
• Side effects of doxycycline and tetracycline that are similar include diarrhea or loose stools, nausea, abdominal pain, vomiting, discoloration of teeth if used in patients below 8 years of age, and exaggerated sunburn (photosensitivity).
• Side effects of tetracycline that are different from doxycycline include rash, headache, and dizziness.

Doxycycline is a synthetic (man-made) antibiotic derived from tetracycline. Doxycycline is used for many different types of infections, including respiratory tract infections due to Hemophilus influenzae, Streptococcus pneumoniae, or Mycoplasma pneumoniae. It also is used for the treatment of non-gonococcal urethritis (due to Ureaplasma), Rocky Mountain spotted fever, typhus, chancroid, cholera, brucellosis, anthrax, syphilis, acne, and periodontal disease.

Tetracycline is a broad-spectrum antibiotic, that is, it is active against many different types of bacteria. Tetracycline prevents growth of bacteria by preventing the bacteria from manufacturing proteins that they need to survive. It is effective against Hemophilus influenzae, Streptococcus pneumoniae, Mycoplasma pneumoniae, Chlamydia psittaci, Chlamydia trachomatis, Neisseria gonorrhoeae, and many others. Tetracycline is used for infections of the respiratory tract, urinary tract, and skin; urethritis, typhus, Rocky Mountain spotted fever, certain sexually transmitted diseases (STDs), acne, anthrax, cholera, and H. pylori.

Doxycycline

Doxycycline is generally well-tolerated. The most common side effects are

• diarrhea or loose stools,
• nausea,
• abdominal pain, and
• vomiting.

Tetracyclines, such as doxycycline, may cause tooth discoloration if used in persons below 8 years of age. Exaggerated sunburn can occur with tetracyclines; therefore, sunlight should be minimized during treatment.

Tetracycline

Tetracycline is generally well-tolerated. The most common side effects are:

• diarrhea or loose stools,
• nausea,
• abdominal pain,
• rash,
• vomiting.
• headache and
• dizziness

Tetracycline may cause discoloration of teeth if used in patients below 8 years of age. Exaggerated sunburn can occur with tetracycline (photosensitivity). Therefore, sunlight or sunlamp exposure should be minimized during treatment.

Doxycycline

• 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.

Tetracycline

• Food or dairy products reduce the absorption of tetracycline. Therefore, tetracycline should be taken at least two hours before or after meals.
• For most infections, tetracycline is taken two to four times daily for 7 to 14 days.
• The usual adult dose is 1-2 g/day in 2 or 4 divided doses.

Doxycycline

• It is recommended that doxycycline not be taken 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. It may also reduce the effect of oral contraceptives. Combining tetracycline and methoxyflurane (Penthrane) may reduce kidney function.

Tetracycline

• Since bacteriostatic drugs like tetracycline may interfere with the bactericidal action of penicillin, it is advisable to avoid giving tetracycline in conjunction with penicillin.
• Because the tetracyclines have been shown to depress plasma prothrombin activity, patients who are on anticoagulant therapy may require downward adjustment of their anticoagulant dosage.
• Absorption of tetracycline is impaired by antacids containing aluminum, calcium, or magnesium, and iron containing preparations.
• Concurrent use of tetracycline may render oral contraceptives less effective.
• The concurrent use of tetracycline and methoxyflurane has been reported to result in fatal renal toxicity.

Doxycycline

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 physician must decide whether to recommend that a nursing mother discontinue nursing during treatment with tetracyclines or change to a different antibiotic.

Tetracycline

Tetracycline is secreted into breast milk. Since tetracycline can impair the development of bone in infants, nursing mothers should not use tetracycline.