November 28, 2015
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(doxycycline hyclate) Delayed-release Capsules

To reduce the development of drug-resistant bacteria and maintain the effectiveness of DORYX® and other antibacterial drugs, DORYX should be used only to treat or prevent infections that are proven or strongly suspected to be caused by bacteria.


DORYX Capsules contain specially coated pellets of doxycycline hyclate, a broad -spectrum antibacterial synthetically derived from oxytetracycline, in a delayed-release formulation for oral administration.

The structural formula for doxycycline hyclate is:

DORYX® (doxycycline hyclate) Structural Formula Illustration

with a molecular formula of C22H24N2O8, HCl, ½ C2H6O, ½ H2O and a molecular weight of 512.9. The chemical designation for doxycycline hyclate is [4S(4aR,5S,5aR,6R,12aS)]-4-(dimethylamino)1,4,4a,5,5a,6,11,12a-octahydro-3,5,10,12,12a-pentahydroxy-6-methyl-1,11-deoxonapthtacene-2carboxamide monohydrochloride, compound with ethyl alcohol (2:1), monohydrate.

Doxycycline hyclate is a yellow crystalline powder soluble in water and in solutions of alkali hydroxides and carbonates. Doxycycline has a high degree of lipid solubility and a low affinity for calcium binding. It is highly stable in normal human serum. Doxycycline will not degrade into an epianhydro form.

Inactive ingredients in the capsule formulation are: lactose; microcrystalline cellulose; povidone, starch wheat, magnesium stearate; cellulosic polymer coating. The capsule shell and/or band contains FD and C blue No. 1; FD and C yellow No. 6; D and C yellow No. 10; gelatin, silicon dioxide; sodium lauryl sulfate; titanium dioxide.

What are the possible side effects of doxycycline?

Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have a serious side effect such as:

  • severe headache, dizziness, blurred vision;
  • fever, chills, body aches, flu symptoms, swollen glands, rash or itching, joint pain, or general ill feeling;
  • urinating less than usual or not at all;
  • diarrhea that is watery or bloody
  • pale or yellowed skin, dark colored urine, fever, confusion or weakness;
  • severe pain in...

Read All Potential Side Effects and See Pictures of Doryx »

What are the precautions when taking doxycycline hyclate (Doryx)?

See also Side Effects section.

Before taking doxycycline, tell your doctor or pharmacist if you are allergic to it; or to other tetracyclines (such as minocycline); or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of: trouble swallowing, esophagus problems (such as hiatal hernia or reflux/heartburn).

Before having surgery, tell your doctor or dentist that you are taking this medication.

This medication may make you more sensitive to the sun. Avoid prolonged sun exposure, tanning booths, and sunlamps. Use a sunscreen and wear protective...

Read All Potential Precautions of Doryx »

Last reviewed on RxList: 9/17/2015
This monograph has been modified to include the generic and brand name in many instances.

Doryx - User Reviews

Doryx User Reviews

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Report Problems to the Food and Drug Administration


You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.

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