Doxycycline

Doxycycline hyclate

Approved uses

• Treatment: Doxycycline is indicated for the treatment of the following infections: Rocky Mountain spotted fever, typhus fever and the typhus group, Q fever, rickettsialpox, and tick fevers caused by Rickettsiae.
• To reduce the development of drug-resistant bacteria and maintain effectiveness of doxycycline hyclate and other antibacterial drugs, doxycycline hyclate should be used only to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria.
• When culture and susceptibility information are available, they should be considered in selecting or modifying antibacterial therapy.
• In the absence of such data, local epidemiology and susceptibility patterns may contribute to the empiric selection of therapy.

Forms and strengths

• Doxycycline hyclate capsules and tablets are available as follows: b.

How it is taken

• The usual dosage and frequency of administration of doxycycline differs from that of the other tetracyclines.
• Exceeding the recommended dosage may result in an increased incidence of side effects.
• Adults: The usual dose of oral doxycycline is 200 mg on the first day of treatment (administered 100 mg every 12 hours) followed by a maintenance dose of 100 mg/day.
• In the management of more severe infections (particularly chronic infections of the urinary tract), 100 mg every 12 hours is recommended.

Must not be used when

• This drug is contraindicated in persons who have shown hypersensitivity to any of the tetracyclines.

Interactions

• Because tetracyclines have been shown to depress plasma prothrombin activity, patients who are on anticoagulant therapy may require downward adjustment of their anticoagulant dosage.
• Since bacteriostatic drugs may interfere with the bactericidal action of penicillin, it is advisable to avoid giving tetracyclines in conjunction with penicillin.
• Absorption of tetracyclines is impaired by antacids containing aluminum, calcium, or magnesium, and iron-containing preparations.
• Absorption of tetracyclines is impaired by bismuth subsalicylate.

Warnings and precautions

• The use of drugs of the tetracycline class during tooth development (last half of pregnancy, infancy and childhood to the age of 8 years) may cause permanent discoloration of the teeth (yellow-gray-brown).
• This adverse reaction is more common during long-term use of the drugs, but it has been observed following repeated short-term courses.
• Enamel hypoplasia has also been reported.
• Use doxycycline in pediatric patients 8 years of age or less only when the potential benefits are expected to outweigh the risks in severe or life-threatening conditions (e.g., anthrax, Rocky Mountain spotted fever), particularly when there are no alternative therapies.

Common side effects

• Due to oral doxycycline's virtually complete absorption, side effects of the lower bowel, particularly diarrhea, have been infrequent. The following adverse reactions have been observed in patients receiving tetracyclines: Gastrointestinal: anorexia, nausea, vomiting, diarrhea, glossitis, dysphagia, enterocolitis, inflammatory lesions (with monilial overgrowth) in the anogenital region, and...

Pregnancy

Teratogenic Effects. There are no adequate and well-controlled studies on the use of doxycycline in pregnant women. The vast majority of reported experience with doxycycline during human pregnancy is short-term, first trimester exposure.

How it acts

Doxycycline inhibits bacterial protein synthesis by binding to the 30S ribosomal subunit. Doxycycline has bacteriostatic activity against a broad range of Gram-positive and Gram-negative bacteria. Resistance Cross resistance with other tetracyclines is common.

Label holder:

PD-Rx Pharmaceuticals, Inc.

Label version:

20 July 2026

This section reports the approved product information. The wording is condensed from the regulator's own summary, and the full document is linked under Sources.