Doxycycline Hyclate (Vibramycin)

  • Generic names: Doxycycline Hyclate; Doxycycline Monohydrate; Doxycycline Calcium
  • Brand names: Doryx, Doxy 100, Vibramycin, Adoxa, Monodox, Oracea, Periostat
  • Therapeutic class: Tetracycline antibiotic

What is Doxycycline used for?

  • Respiratory tract infections
  • Urinary tract infections
  • Acne, rosacea, cellulitis
  • Sexually transmitted diseases (syphilis, chlamydia, gonorrhea).
  • Lyme disease, tick bites, traveler's diarrhea, and malaria
  • Doxycycline is the most effective antibiotic for Rickettsial infections (Rocky Mountain spotted fever, typhus, Q fever) and brucellosis.
  • Recommended by AAP and CDC as drug of choice for presumed or confirmed Rickettsial infection or ehrlichiosis in children of any age4.

Doxycycline is available in several different salts: monohydrate, hyclate (hydrochloride anhydrous), carrageenate, calcium, and phosphate (fosfatex). The therapeutic properties of the different salts do not significantly differ.

Difference between Doxycycline Hyclate vs Monohydrate

Doctors often write prescriptions for doxycycline without specification of which formulation to dispense. Both doxycyclines are equally effective. But sometimes medical practitioners prefer the monohydrate salt because it dissolves slower in the stomach and potentially has less gastrointestinal side effects than standard doxycycline hyclate capsules or tablets 1.

However, an increased stomach pH decreases the bioavailability of doxycycline monohydrate whereas the absorption of hyclate is independent of pH. Plus monohydrate version is more expensive.

Difference between Doryx and Doxycycline

Doryx is a delayed-release formulation of doxycycline hyclate marketed by Warner Chilcott. The essential difference is Doryx contains specially enteric-coated pellets of doxycycline that pass through the stomach and dissolve only after reaching the small intestine. This helps to reduce gastrointestinal irritation. Doryx can be taken once a day anytime, with or without food or milk.

And, of course, the cost of doxycycline is significantly lower in comparison with Doryx.

Is Oracea different from Doxycycline?

Oracea is a 40 mg capsule of doxycycline monohydrate, containing 30 mg immediate-release and 10 mg delayed-release doxycycline beads. It is licenced for the treatment of rosacea only. The dosage of Oracea differs from that of doxycycline used to treat infections.

Long-term risks of Doxycycline

Prolonged use of doxycycline is usually safe 2. According to the UK Advisory Committee for Malaria Prevention (ACMP), there is no evidence of harm in long-term use of doxycycline and it may be taken safely for periods of at least up to two years3.

Foreign names

  • Doxycyclin (Austria, Germany, Switzerland)
  • Doxiciclina (Spain, Portugal)

Drug interactions

  • Antacids (aluminum-, calcium-, or magnesium-containing): decreased doxycycline absorption. Take antacids 1-2 hours before or after doxycycline.
  • Bismuth subsalicylate: decreased absorption of doxycycline, concomitant use not recommended.
  • Iron-containing preparations (oral only): decrease the absorption of doxycycline. Take doxycycline 2 hours before or 3 hours after iron supplements.
  • Retinoids: concomitant use increases the risk of pseudotumor cerebri. Isotretinoin (Accutane) is of particular concern. Exceptions: Adapalene; Alitretinoin; Tretinoin (Topical).


  • 1. Tan KR, Magill AJ, Parise ME, Arguin PM. Doxycycline for malaria chemoprophylaxis and treatment: report from the CDC expert meeting on malaria chemoprophylaxis. Am J Trop Med Hyg. 2011 Apr;84(4):517-31 PubMed
  • 2. Meropol SB, Chan KA, Chen Z, et al. Adverse events associated with prolonged antibiotic use. Pharmacoepidemiol Drug Saf. 2008 May;17(5):523-32. PubMed
  • 3. Hughes C, Tucker R, Bannister B, Bradley DJ. Malaria prophylaxis for long-term travellers. Commun Dis Public Health. 2003 Sep;6(3):200-8.
  • 4. Committee on Infectious Diseases, American Academy of Pediatrics. Red book: 2003 report of the Committee on Infectious Diseases. 26th ed. Elk Grove Village, IL: American Academy of Pediatrics; 2003.

Last updated: February, 2015

Advanced Consumer Info

Doxycycline 100mg
  • Pregnancy Category: D
  • Breastfeeding: Not recommended, though it is NOT contraindicated. Short courses of 7-10 days are considered safe.
  • Elimination half-life:18-22 hours
  • Mechanism of action: Doxycycline is a broad-spectrum bacteriostatic antibiotic that inhibit protein synthesis. Doxycycline has antibacterial, anti-inflammatory, and disease-modifying properties.
  • Advantages:
    Doxycycline is fecally eliminated and can be used in patients with kidney failure.