WHO Guidelines on the Treatment of Chlamydia trachomatis Infection
Guidelines on treatment of Chlamydia trachomatis infection by the World Health Organization (WHO) are summarized below. 
Uncomplicated Genital Chlamydia
WHO recommendations for the treatment of uncomplicated genital chlamydia are as follows:
Azithromycin 1 g orally as a single dose or
Doxycycline 100 mg orally twice a day for 7 days or one of these alternatives: tetracycline 500 mg orally 4 times a day for 7 days, erythromycin 500 mg orally twice a day for 7 days, or ofloxacin 200-400 mg orally twice a day for 7 days
Anorectal Chlamydial Infection
In anorectal chlamydial infection, the WHO recommends doxycycline 100 mg orally twice a day for 7 days over azithromycin 1 g orally as a single dose.
Chlamydial Infection in Pregnant Women
WHO recommendations for the treatment of chlamydial infection in pregnancy are as follows:
Azithromycin recommended over erythromycin
Azithromycin recommended over amoxicillin
Amoxicillin recommended over erythromycin
Azithromycin 1 g orally as a single dose or
Amoxicillin 500 mg orally 3 times a day for 7 days or
Erythromycin 500 mg orally twice a day for 7 days
WHO recommendations for the treatment of lymphogranuloma venereum (LGV) are as follows:
In adults and adolescents with LGV, the guidelines suggest doxycycline 100 mg orally twice daily for 21 days over azithromycin 1 g orally weekly for 3 weeks.
Good practice dictates treatment of LGV, particularly for men who have sex with men and for people with HIV infection.
When doxycycline is contraindicated, azithromycin should be provided.
When neither treatment is available, erythromycin 500 mg orally 4 times a day for 21 days is an alternative.
Doxycycline should not be used in pregnant women.
The goals of pharmacotherapy are to reduce morbidity and to prevent complications. Agents used in the management of chlamydial genitourinary infections are treated primarily by administering antibiotics. Treatment of genitourinary chlamydial infection clearly is indicated when the infection is diagnosed or suspected; for sexual partners of the index case; and for patients being treated for gonorrhea.
The Centers for Disease Control and Prevention (CDC) recommends azithromycin and doxycycline as first-line drugs for the treatment of chlamydial infection. Second-line drugs (eg, erythromycin, penicillins, and sulfamethoxazole) are less effective and have more adverse effects.
Azithromycin (Zithromax, Zmax)
Azithromycin is a relatively new member macrolide antibiotic that possesses activity against various different bacterial organisms. It binds to the 50S ribosomal subunit of the bacteria, thereby inhibiting bacterial protein synthesis. Related to erythromycin, azithromycin is considered by many to be the treatment of choice for Chlamydia trachomatis genitourinary infection because it may be administered in a single dose, which improves adherence to treatment.
Doxycycline (Adoxa, Doryx, Monodox, Avidoxy, Vibramycin)
Doxycycline, a well-absorbed tetracycline derivative, is the second drug of choice for genital chlamydia infections. It has a limited spectrum of bacterial activity but is effective in treating chlamydial infections. Doxycycline binds to the 30S and, possibly, 50S ribosomal subunits of the bacteria, thereby inhibiting bacterial protein synthesis.
One week of doxycycline appears to be as effective as a single dose of azithromycin for treating genitourinary chlamydial infections. Although the course is longer than that of azithromycin, the cost is less, and doxycycline has been used in clinical practice for a much longer time. Because of the need for extended therapy, compliance is often poor.
For pseudomonal infections and infections due to multidrug-resistant gram-negative organisms.
Penetrates prostate well and is effective against N gonorrhea and C trachomatis.
A pyridine carboxylic acid derivative with broad-spectrum bactericidal effect.
Erythromycin (E.E.S., Ery-Tab, Erythrocin, EryPed, PCE)
Erythromycin is a macrolide antibiotic with a large spectrum of activity. It binds to the 50S ribosomal subunit of the bacteria, thereby inhibiting bacterial protein synthesis. Generally, erythromycin is considered a recommended treatment for chlamydial genitourinary infection only in pregnant women. Some recommend it in infants as well.
Second-generation cephalosporin with activity against some gram-positive cocci, gram-negative rod infections, and anaerobic bacteria. Inhibits bacterial cell wall synthesis by binding to one or more of the penicillin-binding proteins; inhibits final transpeptidation step of peptidoglycan synthesis, resulting in cell wall death.
Infections caused by cephalosporin- or penicillin-resistant gram-negative bacteria may respond to cefoxitin.
Like erythromycin, ampicillin is considered a recommended treatment for genitourinary chlamydial infection only in pregnant women. Ampicillin binds to penicillin-binding proteins, which inhibit bacterial cell wall synthesis by inhibiting the final transpeptidation step of peptoglycan synthesis in bacterial cell wall. This in turn causes the bacteria to lyse due to ongoing activity of cell wall autolytic enzymes.
Because of its lower efficacy, amoxicillin is indicated only when the patient is both pregnant and erythromycin-allergic. Amoxicillin is a penicillin antibiotic with activity against gram-positive and some gram-negative bacteria. It binds to penicillin-binding proteins, thereby inhibiting bacterial cell wall growth.
Second-generation cephalosporin used as single-drug therapy to provide broad gram-negative coverage and anaerobic coverage. Also provides some coverage of gram-positive bacteria. Half-life is 3.5 h. Inhibits bacterial cell wall synthesis by binding to one or more of the penicillin-binding proteins; inhibits final transpeptidation step of peptidoglycan synthesis, resulting in cell wall death.
Dosage and route of administration depends on condition of patient, severity of infection, and susceptibility of causative organism.
Clindamycin (Cleocin, CLIN Single Use)
Lincosamide for treatment of serious skin and soft tissue staphylococcal infections. Effective against aerobic and anaerobic streptococci (except enterococci). Inhibits bacterial growth, possibly by blocking dissociation of peptidyl t-RNA from ribosomes, causing RNA-dependent protein synthesis to arrest.
Gentamicin is an aminoglycoside antibiotic for gram-negative coverage. It is used in combination with an agent against gram-positive organisms and one that covers anaerobes.
This combination of a beta-lactamase inhibitor and ampicillin interferes with bacterial cell wall synthesis during active replication, causing bactericidal activity against susceptible organisms.
Metronidazole (Flagyl, Flagyl ER, Metro)
Metronidazole is active against various anaerobic bacteria and protozoa. It appears to be absorbed into the cells; the intermediate metabolized compounds that are formed bind DNA and inhibit protein synthesis, causing cell death.