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Antibiotics for Chlamydia Infection

What is a Chlamydia infection?

Chlamydia is a common sexually transmitted disease (STD) caused by the bacteria Chlamydia trachomatis.

C. trachomatis is the most common sexually transmitted bacteria in the United States. The Centers for Disease Control and Prevention (CDC) estimates 2.8 million people are infected each year. Up to 70% of infections associated with few or no symptoms.

Women are more likely to be asymptomatic than men (80% vs 50%). However, women are more likely to develop long-term complications.


Chlamydia can be transmitted during vaginal, anal, and, although less likely, oral sex. Chlamydia can also be passed from an infected mother to her baby during vaginal childbirth. The bacteria also can infect your throat if you have oral sexual contact with an infected partner.

Chlamydia can be transmitted even if the penis or tongue does not enter the vagina, mouth, or rectum. Using latex condoms consistently and correctly - from the very beginning of sexual contact until there is no longer skin contact - reduces the risk of transmission of chlamydia.


Chlamydia is known as an asymptomatic or "silent" disease because about 75% of infected women and about 50% of infected men have no symptoms until the the infection has become advanced. If symptoms do occur, they usually appear within 1 to 3 weeks after exposure.

In women, the bacteria initially infect the cervix and the urethra (urine canal). Women who have symptoms might have an abnormal vaginal discharge or a burning sensation when urinating. When the infection spreads from the cervix to the fallopian tubes (tubes that carry fertilized eggs from the ovaries to the uterus), some women still have no signs or symptoms; others have lower abdominal pain, low back pain, nausea, fever, pain during intercourse, or bleeding between menstrual periods. Chlamydial infection of the cervix can spread to the rectum.

Men with signs or symptoms might have a discharge from their penis or a burning sensation when urinating. Men might also have burning and itching around the opening of the penis. Pain and swelling in the testicles are uncommon.

Men or women who have receptive anal intercourse may acquire chlamydial infection in the rectum, which can cause rectal pain, discharge, or bleeding. Chlamydia can also be found in the throats of women and men having oral sex with an infected partner.


Even though symptoms of chlamydia are usually mild or absent, serious complications can occur. If untreated, chlamydial infections can progress to serious reproductive and other health problems with both short-term and long-term consequences.

In women, untreated infection can spread into the uterus or fallopian tubes and cause pelvic inflammatory disease (PID). This happens in up to 40% of women with untreated chlamydia. PID can cause permanent damage to the fallopian tubes, uterus, and surrounding tissues. The damage can lead to chronic pelvic pain, infertility, and potentially fatal ectopic pregnancy (pregnancy outside the uterus).

Untreated chlamydia in men typically causes infection of the urethra, the tube that carries urine from the body. Infection sometimes spreads to the tube that carries sperm from the testis, causing epididymitis (inflammation of the reproductive area near the testicles). This may cause pain, fever, and even infertility.

Rarely, genital chlamydial infection can cause arthritis that can be accompanied by skin lesions and inflammation of the eye and urethra (Reiter's syndrome).

In pregnant women, chlamydia infections may lead to premature delivery. Babies born to infected mothers can get infections in their eyes, called conjunctivitis or pinkeye, as well as pneumonia. Both of these health problems can be treated with antibiotics.

Antibiotics for Chlamydia infection

Chlamydia can be easily treated and cured with antibiotics. However, not all antibiotics are effective. The antibiotics usually used are azithromycin and doxycycline.

Persons with chlamydia should abstain from sexual intercourse until they and their sex partners have completed treatment, otherwise re-infection is possible.

First-choice antibiotics

What is the best antibiotic to cure chlamydia?

The Centers for Disease Control and Prevention recommends doxycycline or azithromycin as first-choice antibiotic for the treatment of chlamydia infection. These medications are very effective for both acute and persistent infections.

A recent analysis of 12 randomized clinical trials of azithromycin versus doxycycline for the treatment of genital chlamydial infection demonstrated that the treatments were equally efficacious, with microbial cure rates of 97% and 98%, respectively2.


Doxycycline is an old proven and reliable treatment with cure rates exceeding 90%. Most new treatments are compared against this antibiotic. However, doxycycline is contraindicated during pregnancy and breastfeeding.

Doxycycline is less expensive than azithromycin, and it has been used extensively for a longer period. However, its dosage regimen is less convenient.

Doxycycline dosage: 100 mg orally twice a day for 7 days for urogenital chlamydial infection (chlamydial urethritis and cervicitis).

Azithromycin (Zithromax)

Azithromycin has in many ways revolutionized the treatment of chlamydial infections. It is one of the most widely studied antibiotics for chlamydia and provides a cure rate of 96%6.

Azithromycin is particularly effective for chronic persistent genital chlamydia.

The advantage of azithromycin is that it works after taking a single dose. But you'll need to wait seven days after having treatment before having sex again.

Chlamydia during pregnancy
Azithromycin is also recommended as a first-line treatment for genital chlamydial infection during pregnancy. There is evidence supporting azithromycin as safe and effective in pregnant women4.

Chlamydia associated with infertility
New research from the Safdarjung Hospital7 suggests that azithromycin with its broader immunomodulatory effects may be preferable to doxycycline for the treatment of recurrent C. trachomatis infection associated with infertility.

Azithromycin dosage: 1 g orally in a single dose.

Alternative dosage regimen: 500 mg in a single dose on day 1 followed by 250 mg once daily for 2 days5.

Alternative regimens


Another antibiotic that's likely to work for chlamydia is erythromycin. Doctors sometimes prescribe it. Erythromycin treatment does not work as well as the other recommended antibiotics. It is cheap and can be used in pregnancy. Erythromycin's disadvantages are its lengthy dosing (four times daily), gastrointestinal disturbance which leads to discontinuation, and a less than 95% efficacy.

Erythromycin dosage: 500 mg orally 4 times a day 7 days.
Erythromycin ethylsuccinate dosage: 800 mg orally 4 times a day 7 days.

Ofloxacin and levofloxacin are effective treatment alternatives but are more expensive and offer no advantage in the dosage regimen. Other quinolones either are not reliably effective against chlamydial infection or have not been evaluated adequately.


Ofloxacin is similar in efficacy to doxycycline and azithromycin (more than 95%), has good side-effect profile. But it is more expensive to use and offers no advantage with regard to the dosage regimen. Ofloxacin cannot be taken in pregnancy.

Ofloxacin dosage: 300 mg orally twice a day for 7 days.

Levofloxacin (Levaquin)

Levofloxacin (Levaquin) has been successfully evaluated for treatment of chlamydia infection in clinical trials8. Because its pharmacology and in vitro microbiologic activity are similar to that of ofloxacin, levofloxacin may be substituted in doses of 500 mg once a day for 7 days.

Levofloxacin dosage: 500 mg orally for 7 days.

Other fluoroquinolones, in particular Ciprofloxacin (Cipro), are NOT sufficiently effective against Chlamydia species.

Antibiotics recommended in pregnant women

There's some good evidence that azithromycin, erythromycin and amoxicillin are likely to work for pregnant women who have chlamydia.


Amoxicillin is a recommended treatment of Chlamydia infection during pregnancy by Centers for Disease Control and Prevention. However, it is not the best antibiotic for eradication of Chlamydia in other categories of people.

Amoxicillin dosage: 500 mg orally 3 times a day for 7 days.

  • 1. Sexually Transmitted Diseases Treatment Guidelines 2010 Centers for Disease Control and Prevention
  • 2. Lau C-Y, Qureshi AK. Azithromycin versus doxycycline for genital chlamydial infections: a meta-analysis of randomized clinical trials. Sex Transmit Dis 2002;29:497502.
  • 3. Chlamydial Infections: Urethritis and Cervicitis STD Treatment Guidelines 2010 Centers for Disease Control and Prevention
  • 4. Rahangdale L, Guerry S, Bauer HM, et al. An observational cohort study of Chlamydia trachomatis treatment in pregnancy. Sex Transm Dis. 2006;33(2):106-110.
  • 5. Whatley JD, Thin RN, Mumtaz G, Ridgway GL. Azithromycin vs doxycycline in the treatment of non-gonococcal urethritis. 1991 Jul-Aug;2(4):248-51.
  • 6. Miller JM. Efficacy and Tolerance of Single-dose Azithromycin for Treatment of Chlamydial Cervicitis During Pregnancy. Infect Dis Obstet Gynecol. 1995;3(5):189-92
  • 7. Srivastava P, Bhengraj AR, Jha HC, Vardhan H, Jha R, Singh LC, Salhan S, Mittal A. Differing effects of azithromycin and doxycycline on cytokines in cells from Chlamydia trachomatis-infected women. DNA Cell Biol. 2012 Mar.
  • 8. Mikamo H, Yamagishi Y, Takahashi K, et al. Clinical study of levofloxacin 500 mg qd in the treatment of cervicitis and intrauterine infections caused by Chlamydia trachomatis. Jpn J Antibiot. 2011 Aug;64(4):217-29.

Published: January 20, 2009
Last updated: January 05, 2014