Doxycycline vs. Bactrim: What's the difference?

What is Doxycycline? What is Bactrim?

Doxycycline is an antibiotic in the tetracycline class used to treat many infections, including respiratory tract infections due to Hemophilus influenzae, Streptococcus pneumoniae, or Mycoplasma pneumoniae. It is also used to treat non-gonococcal urethritis (due to Ureaplasma), typhus, anthrax, brucellosis, chancroid, cholera, Rocky Mountain spotted fever, syphilis, acne, and, periodontal disease.

Bactrim (sulfamethoxazole and trimethoprim) is an antibiotic that contains an anti-bacterial sulfonamide (a "sulfa" drug) and an inhibitor of the production of tetrahydrofolic acid. Bactrim is used to treat urinary tract infections, flares of chromic bronchitis due to bacteria, middle ear infections, to prevent infections due to pneumococcus in organ transplant recipients, to treat or prevent Pneumocystis carinii pneumonia, chancroid, and to prevent toxoplasma encephalitis in patients with AIDS.

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What are the side effects of doxycycline and Bactrim?

Doxycycline

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

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.

Bactrim

Common side effects of sulfamethoxazole/trimethoprim are:

Other side effects include:

What is the dosage of doxycycline vs. Bactrim?

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.

Bactrim

  • The recommended adult dose for urinary tract infections is one double strength tablet (Bactrim DS, Septra DS) or two single strength tablets every 12 hours for 10 to 14 days.
  • Flares of chronic bronchitis are treated with a similar regimen for 14 days.
  • Sulfamethoxazole/trimethoprim should be taken with 6 to 8 ounces of liquid to prevent crystals from forming in the urine. Persons with advanced kidney disease may require lower doses.

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What drugs interact with doxycycline and Bactrim?

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.

Bactrim

Sulfamethoxazole/trimethoprim can enhance the blood-thinning effects of warfarin (Coumadin), possibly leading to bleeding. Sulfonamides such as sulfamethoxazole can increase the metabolism (break-down and elimination) of cyclosporine (causing loss of effectiveness of cyclosporine), and can add to the kidney damage caused by cyclosporine.

All sulfonamides can crystallize in urine when the urine is acidic. Since methenamine (Hiprex, Urex, Mandelamine) causes acidic urine, it should not be used with sulfonamides.

Blood levels of phenytoin (Dilantin) may be increased by treatment with sulfamethoxazole/trimethoprim. This may lead to side effects associated with phenytoin (Dilantin, Dilantin-125) such as dizziness, and reduced attention.

Sulfamethoxazole/trimethoprim also may increase blood levels of digoxin (Lanoxin) and possibly lead to serious toxic effects. Anemia, due to a reduction in folic acid, can occur in persons receiving sulfamethoxazole/trimethoprim in combination with:

Increased blood levels of potassium may occur when sulfamethoxazole/trimethoprim is combined with ACE inhibitors.

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Are doxycycline and Bactrim safe to use while pregnant or breastfeeding?

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.

Bactrim

Use of sulfonamides may cause bilirubin to be displaced from proteins in the infant's blood. Displacement of bilirubin can lead to jaundice and a dangerous condition called kernicterus in the infant. For this reason, sulfamethoxazole/trimethoprim should not be used near term (late in pregnancy) among women.

Sulfamethoxazole/trimethoprim should not be used by nursing mothers because sulfamethoxazole is excreted in milk and can cause kernicterus.

Summary

Doxycycline and Bactrim (sulfamethoxazole and trimethoprim) are antibiotics used to treat many different types of bacterial infections. Doxycycline and Bactrim are different types of antibiotics. Doxycycline is a tetracycline antibiotic and Bactrim contains an anti-bacterial sulfonamide (a "sulfa" drug) and an inhibitor of the production of tetrahydrofolic acid.

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Medically Reviewed on 5/13/2019
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