Examples

How It Works

Tetracyclines make it difficult for bacteria to reproduce.

Why It Is Used

Doctors use tetracyclines to treat lower respiratory tract infections in otherwise healthy people younger than 65. These medicines are an alternative antibiotic when you cannot take one of the macrolide antibiotics.

Doxycycline is not effective against some types of Streptococcus pneumoniae, the bacteria that cause most identified cases of pneumonia. This is because the bacteria are resistant to it.

How Well It Works

In general, all antibiotics used have a high cure rate for pneumonia. For people in the hospital, cure rates are 73% to 96%. Outside of the hospital, cure rates are generally above 80%.¹

Tetracyclines are effective against some types of Mycoplasma pneumoniae, Streptococcus pneumoniae, Chlamydial pneumoniae, and Haemophilus influenzae. But bacteria that are resistant to tetracycline are common.

You most likely will see some improvement in symptoms within 2 to 3 days after beginning treatment. Unless you get worse during that time, your treatment will not change for at least 3 days. The number of days you continue to take antibiotics depends on your illness and the type of antibiotic.

Side Effects

The most common side effects of tetracyclines include:

• Increased sensitivity to sun (sunburn easily).
• Stomach upset, nausea, vomiting.
• Dizziness.
• Sore mouth.

Doctors do not use tetracyclines for children younger than age 8 because the medicine can discolor a child's teeth.

See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)

What To Think About

Tetracyclines are less expensive than some other antibiotics, but certain strains of bacteria may be resistant to them.

You should not take tetracyclines with dairy products (such as milk or cheese) because this can affect the way your body absorbs the medicines.

Complete the new medication information form (PDF)(What is a PDF document?) to help you understand this medication.

Citations

1. Loeb M (2006). Community acquired pneumonia, search date April 2005. Online version of Clinical Evidence (15): 1–10.