Doxycycline is part of the tetracycline group of antibiotics and is approved for treatment of a variety of bacterial infections. Doxycycline is synthetically derived from oxytetracycline. It is available as doxycycline hydrochloride hemiethanolate hemihydrate.2 Tetracyclines inactivate several enzymes that play a role in inflammation. Doxycycline is primarily bacteriostatic (stops bacterial growth) and thought to exert its antimicrobial effect by the inhibition of protein synthesis. Doxycycline is active against a wide range of gram-positive and gram-negative organisms.

Doxycycline differ form tetracycline in that it has higher tissue penetration, higher intracellular penetration, larger volumes of distribution, and better antimicrobial properties. More of the drug is excreted in the intestine.5

Use of Doxycycline

It is used to treat Lyme disease, acne, cholera, and sexually transmitted diseases (STDs).1 It is also used in some areas for the treatment for chloroquine-resistant malaria.

Chlamydia is a sexually transmitted disease (STD) caused by the bacteria Chlamydia trachomatis. The bacteria live in the semen and vaginal fluid, and infected persons may or may not have symptoms of infection. When doxycyline is given for one week, it appears to be just as effective as a single-dose of azithromycin (an antibiotic) for chlamydia infection. A study of the activity of antibiotics on chlamydia, noted that the use of doxycycline for several years might be responsible for the high level of resistance to this drug in some regions of the world. When compared with other drugs, doxycycline showed the least activity on the Chlamydia trachomatis bacterium.1

Potential Side Effects

Tetracyclines have long been used to treat a wide variety of medical conditions, especially in the field of dermatology. Unfortunately, safety concerns, especially gastrointestinal (GI), have always been present. Other safety concerns have included tooth development in children, candidiasis, vestibular concerns, photosensitivity/phototoxicity, and more unusual adverse effects such as uncontrolled hypertension.4

Skin reactions related to sun exposure (photosensitivity reaction), rash, hives, permanent discoloration of teeth ( when administered during tooth development), anorexias, diarrhea, difficulty swallowing, various blood abnormalities, anemia, decreased kidney function, stomach upset.1

Usage in Pregnancy

Doxycycline should not be used in pregnant women unless, in the judgment of the physician, it is essential for the welfare of the patient. Results of animal studies indicate that tetracyclines cross the placenta, are found in fetal tissues and can have toxic effects on the developing fetus (often related to retardation of skeletal development).3

Pediatric Use

The use of doxycycline in pediatric patients under 8 years is not recommended because safe conditions for its use have not been established.3

Drug Interaction

Digoxin, warfarin, antacids containing aluminum, calcium, or magnesium, iron, bismuth subsalicylate, barbiturates, zinc salts, phenytoin, sucralfate, didanosine, quinapril, mirtazapine, nateglinide, nefazodone, quinidine, sildenafil, tadalafil, vardenafil, tacrolimus, venlafaxine, midazolam, triazolam, ergot alkaloids, lovastatin, simvastatin, mesoridazine, didanosine, quinapril, penthrane, oral anticoagulants and carbamazepine.

Food Interactions

Blood levels may be decreased if taken with food or milk. Administration with iron or calcium may decrease absorption. May decrease absorption or iron, calcium, magnesium, zinc, and amino acids. Avoid chronic alcohol ingestion.

Special Information

Although food may decrease the absorption of doxycycline, it may be necessary to take with food to prevent stomach upset. Do not chew.1

Doxycycline Hyclate

Doxycycline hyclate is a tetracycline derivative having reduced antimicrobial activity; it is used for periodontal diseases. Alternative names: Vibramycin, doxycycline hydrochloride, Doxy, Periostat.

Usage of Doxycycline in Animals

Doxycycline is commonly used in small animals (tablets and oral suspension). Doxycycline is the first drug of choise in the treatment of tick-borne infections caused by Ehrlichia canis and Rickettsiae, leptospirosis as well as Mycoplasma hemofelis. It has been proved effective for the treatment of bartonellosis. An important use of doxycycline is in birds. Doxycycline has become a treatment of choice for psittacosis.5


  1. Prescription Drugs: Alternative Uses, Alternative Cures. Kevin Loughlin, Joyce Generali
  2. Doxycycline. PubChem Substance
  3. Doxycycline. DailyMed
  4. The use and safety of doxycycline hyclate and other second-generation tetracyclines. Expert Opin Drug Saf 2008,Sep,01;7(5):571-7; (PMID: 18759709). Sloan, Barry ; Scheinfeld, Noah
  5. Veterinary Pharmacology and Therapeutics. Jim E. Riviere, Mark G. Papich