Generic name: Doxycycline hyclate.

Other brand names: Doxy-Caps, Doxychel Hyclate, Vibramycin, Vibra-Tabs.

Doryx is a tetracycline antibiotic. It interferes with the production of certain biochemicals necessary for bacteria to sustain life. 

Quick Facts About Doryx


Used to treat a range of bacterial infections, including: Rocky Mountain spotted fever and other fevers caused by ticks, fleas, and lice; amoebic dysentery; some gonococcal infections in adults; severe acne; trachoma; and urinary tract infections. Also used to prevent malaria on trips of 4 months or less.

Doryx Dosage

Take with a full glass of water or other liquid to avoid throat or stomach irritation. May be taken with or without food. Tablets should be swallowed whole. If taking oral suspension, shake well before using; do not use expired medication.

  • Usual adult dose: 200 milligrams on the first day of treatment, followed by a maintenance dose of 100 milligrams per day. Maintenance dose may be as a single dose or 50 milligrams every 12 hours. For chronic urinary tract infections — 100 milligrams every 12 hours. For uncomplicated gonorrhea (except anorectal infections in men) — 100 milligrams orally, 2 times per day for 7 days, or 300 milligrams in a single dose followed by 300 milligrams I hour later. For primary and secondary syphilis — 200 milligrams a day, divided into equal doses for 14 days. For prevention of malaria — 100 milligrams a day, starting 1 to 2 days before travel to destination where malaria is found, then daily during travel, and 4 weeks after leaving.
  • Usual child dose (for children over 8 years): if weighing 100 pounds or less — 2 milligrams per pound of body weight, divided into 2 doses on day one, then 1 milligram per pound of body weight as a single dose or 2 doses on the following days. For severe infections — up to 2 milligrams per pound of body weight. For prevention of malaria — 2 milligrams per 2.2 pounds of body weight up to 100 milligrams.
  • Missed dose: take as soon as possible. If taking 1 dose per day — take next dose 10 to 12 hours after missed dose, then return to regular schedule. If taking 2 doses per day — take next dose 5 to 6 hours after missed dose, then return to regular schedule. If taking 3 doses per day — take next dose 2 to 4 hours after missed dose, then return to regular schedule.

Doryx Side Effects

Overdose symptoms:

no specific information available on overdose. If you suspect an overdose, immediately seek medical attention.

More common side effects: angioedema (chest pain; swelling of face, lips, tongue, throat, arms and legs; difficulty swallowing), bulging foreheads in infants, diarrhea, difficulty swallowing, discolored teeth in infants and children, inflammation of the tongue, loss of appetite, nausea, rash, rectal or genital itching, severe allergic reaction (hives, itching, swelling), skin sensitivity to light, vomiting.

Less common or rare Doryx side effects: aggravation of lupus erythematosus, skin inflammation and peeling, throat inflammation and ulcerations.


Inform your doctor before combining Doryx with:

antacids containing aluminum, calcium, magnesium, or iron-containing preparations such as Maalox and Mylanta; barbiturates such as phenobarbital; muth subsalicylate (Pepto-Bismol); blood thinners such as Coumadin; carbamazepine (Tegretol); oral contraceptives; penicillin (V-Cillin K or Pen*Vee K); phenytoin (Dilantin); sodium bicarbonate. May decrease effectiveness of oral contraceptives containing estrogen.

No known food/other substance interactions.

Special Cautions

Should not use if pregnant; can damage developing teeth during the last half of pregnancy. If pregnant or planning to become pregnant, inform your doctor immediately. Tetracyclines appear in breast milk; can affect a nursing infant.

No special precautions apply to seniors.

Follow doctor’s instructions carefully for children.

  • May permanently discolor developing teeth; should not mir be taken by pregnant women or children under 8 years.
  • Should not take if sensitive to or allergic to this or similar medications. If you have asthma, use very cautiously.
  • Monitor for secondary infection.
  • May cause sensitivity to sunlight; immediately notify your doctor if you develop a skin rash.

Note: provides accurate and independent information prescription pills, over-the-counter medicines and natural products. This material is provided for educational purposes only and is not intended for medical advice, diagnosis or treatment. If you have questions about  dosage, or Doryx side effects, please contact your healthcare provider.