Doxycycline 100 mg (Vibramycin)

  • Generic name: Doxycycline Calcium, Hyclate, Monohydrate
  • Trade names: Doryx, Doxy, Vibramycin (Pfizer), Vibra-Tabs, Periostat
  • Dosages: 100 mg capsules
  • Pharmacologic category: Tetracycline antibiotic
  • FDA approved: 1967
  • Pregnancy risk factor: D
What is Doxycycline?

Doxycycline is a broad-spectrum tetracycline antibiotic that is commonly prescribed to treat infections. Doxycycline is derived from and related to oxytetracycline. It differs from other tetracyclines in that it is more completely absorbed, more lipid-soluble, and has a longer plasma half-life.

Doxycycline indicated uses:

  • Urinary tract infections
  • Respiratory tract infections
  • Gingivitis (Periostat)
  • Acne
  • Sexually transmitted diseases (STDs) such as gonorrhea and chlamydia
  • Inhalational anthrax due to Bacillus anthracis, including postexposure prophylaxis
  • Plague (due to Yersinia pestis), including naturally occurring or endemic bubonic, septicemic, or pneumonic plague
  • Malaria (due to Plasmodium falciparum)
  • Tickborne Rickettsial diseases
  • Lyme disease [6], bartonellosis
  • Trachoma (chronic infections of the eye)
  • Anti-infective prophylaxis in sexual assault victims
Doxycycline for Acne Vulgaris

Doxycycline is effective in the treatment of patients with moderate to severe inflammatory acne vulgaris14. Doxycycline presumably works by decreasing the population of the skin bacterium, Propionibacterium acnes. In addition, Doxycycline exerts various anti-inflammatory and immunomodulatory properties. It reduces lipase production in P. acnes, resulting in a reduction of fatty acids in sebum on the skin surface.

Effectiveness: Doxycycline treatment reduces about 84-90% of acne papules and pustules7.

Doxycycline dosage for Acne: Initial doxycycline dose for treating acne is 100 mg twice daily for 3 to 6 weeks.
Maintenance dose is 50 mg once a day.

Sub-antimicrobial dose of doxycycline (20 mg twice daily) is effective in reducing both inflammatory and non-inflammatory acne lesions and does not change skin flora 7.

How long does it take for doxycycline to work for acne? You may expect to notice visible improvement in acne within 6 weeks. The peak benefit is usually seen after 3-6 months [12].

Doxycycline is useful in rosacea, but rosacea responds much more quickly.

Pharmacological characteristics
  • Metabolism: not hepatic; partially inactivated in GI tract by chelate formation.
  • Elimination half-life: 12-15 hours (usually increases to 22-24 hours with multiple doses);
  • Excretion: Feces (30%); urine (23%)
  • one of the most potent antibiotics
  • anti-inflammatory effects [2, 4]
  • blood and tissue levels are equivalent whether the drug is administered orally or intravenously [3]
  • first line antibiotic for the treatment of chlamydial infections [5]
  • strong antimalarial properties
  • active against the most common bacterial cause of community-acquired pneumonia: Streptococcus pneumoniae, Mycoplasma pneumoniae, and Chlamydia pneumoniae [11]
  • although tetracyclines are usually avoided in the young child, up to 2 weeks of doxycycline therapy can be given safely without risking dental staining
  • contraindicated during pregnancy (pregnancy category D)
  • photosensitivity - doxycycline is a more potent photosensitizer than other tetracyclines
  • expired doxycycline is dangerous and may cause kidney damage
  • risk of esophageal ulceration if the capsules for some reason does not reach the stomach but remains in the oesophagus
  • prolonged IV use may result in thrombophlebitis
Unlabeled uses
  • Enterococcus infections resistant to vancomycin
  • Human ehrlichiosis [8]
  • Rosacea [1]
  • Sarcoidosis [9]
Mode of action

Doxycycline blocks protein synthesis by preventing the binding of aminoacyl-tRNA to the ribosome. Its action is bacteriostatic (preventing the growth of bacteria) rather than killing (bactericidal).

Doxycycline inhibits the nitric oxide synthesis. This activity is a possible pathway by which tetracyclines may function as anti-inflammatory compounds.

  • 1. Quarterman MJ, Johnson DW, Abele DC, Lesher JL Jr, Hull DS, Davis LS. Ocular rosacea. Signs, symptoms, and tear studies before and after treatment with doxycycline. Arch Dermatol. 1997 Jan;133(1):49-54. PubMed
  • 2. Borderie D, Hernvann A, Hilliquin P, Lemarchal H, Kahan A, Ekindjian OG. Tetracyclines inhibit nitrosothiol production by cytokine-stimulated osteoarthritic synovial cells. Inflamm Res. 2001 Aug;50(8):409-14.
  • 3. Bocker R, Estler CJ, Maywald M, Weber D. Comparison of distribution of doxycycline in mice after oral and intravenous application measured by a high-performance liquid chromatographic method. Arzneimittelforschung. 1981;31(12):2116-7.
  • 4. Krakauer T, Buckley M. Doxycycline is anti-inflammatory and inhibits staphylococcal exotoxin-induced cytokines and chemokines. Antimicrob Agents Chemother.. 2003 Nov;47(11):3630-3.
  • 5. Zele-Starcevic' L, Plecko Vanda, Budimir A, Kalenic' S. Choice of antimicrobial drug for infections caused by Chlamydia trachomatis and Chlamydophila pneumoniae. Acta Med Croatica. 2004;58(4):329-33.
  • 6. Borg R, Dotevall L, Hagberg L, Maraspin Vera, Lotric-Furlan S, Cimperman J, Strle F. Intravenous ceftriaxone compared with oral doxycycline for the treatment of Lyme neuroborreliosis. Scand J Infect Dis. 2005;37(6-7):449-54. PubMed
  • 7. Toossi P, Farshchian M, Malekzad F, Mohtasham N, Kimyai-Asadi A. Subantimicrobial doxycycline in the treatment of moderate facial acne. J Drugs Dermatol. 2008 Dec;7(12):1149-52. PubMed
  • 8. Aguero-Rosenfeld ME, Horowitz HW, Wormser GP, McKenna DF, Nowakowski J, Mun~oz J, Dumler JS. Human granulocytic ehrlichiosis: a case series from a medical center in New York State. Ann Intern Med. 1996 Dec 1;125(11):904-8.
  • 9. El Sayed F, Dhaybi R, Ammoury A. Subcutaneous nodular sarcoidosis and systemic involvement successfully treated with doxycycline. J Med Liban. 2006 Jan-Mar;54(1):42-4.
  • 10. Mosam A, Morar N. Recalcitrant cutaneous sarcoidosis: an evidence-based sequential approach. J Dermatolog Treat. 2004 Dec;15(6):353-9.
  • 11. Ragnar Norrby S. Atypical pneumonia in the Nordic countries: aetiology and clinical results of a trial comparing fleroxacin and doxycycline. J Antimicrob Chemother. 1997 Apr;39(4):499-508. PubMed
  • 12. Comprehensive Dermatologic Drug Therapy. p.80
  • 14. Leyden JJ, Bruce S, Lee CS, Ling M, Sheth PB, Stewart DM, Werschler WP, Gilbert RD, Kircik L. A randomized, phase 2, dose-ranging study in the treatment of moderate to severe inflammatory facial acne vulgaris with doxycycline calcium. J Drugs Dermatol. 2013 Jun 1 PubMed

Written for, October 2009.
Last modified: February 10, 2015

Interesting facts


  • Doxycycline was clinically developed in the early 1960s by Pfizer Inc. and marketed under the brand Vibramycin. It is a synthetic broad-spectrum antibiotic derived from tetracycline.
  • Clinically, Doxycycline is shown to be much more active than tetracycline and its therapeutical value continues to be recognized to this day.
  • This antibiotic is not used for children younger than age 9 because it may stain their teeth.

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