“Dox” most commonly refers to doxycycline, a widely prescribed antibiotic in the tetracycline family. It treats a broad range of bacterial infections, from acne and Lyme disease to sexually transmitted infections like chlamydia and syphilis. However, “dox” can also be shorthand for a few other medications, so it’s worth knowing which one applies to you.
Other Medications Called “Dox”
While doxycycline is by far the most common “dox” medication, three others share the abbreviation. Doxazosin is a blood pressure and prostate medication that relaxes the muscles of the bladder, prostate, and blood vessels, making it easier to urinate and lowering blood pressure. Doxepin is used to treat depression at higher doses and insomnia at lower doses. Doxorubicin is a chemotherapy drug used for cancers of the breast, ovary, bladder, and thyroid, as well as leukemia and lymphoma.
If you’re unsure which “dox” medication you’ve been prescribed, check the full name on your pharmacy label. The rest of this article focuses on doxycycline, since that’s what most people mean when they say “dox.”
What Doxycycline Treats
Doxycycline is one of the most versatile antibiotics available. It works by stopping bacteria from building the proteins they need to grow and multiply, which halts an infection without necessarily killing the bacteria outright. This makes it effective against a surprisingly wide variety of conditions.
Its most common uses include:
- Acne: The American Academy of Dermatology recommends doxycycline as the first-choice oral antibiotic for acne when topical treatments aren’t enough.
- Lyme disease: Doxycycline is the preferred treatment for the early-stage rash of Lyme disease, typically prescribed at 100 mg twice daily for 10 to 14 days.
- Sexually transmitted infections: It treats chlamydia, syphilis, gonorrhea, and pelvic inflammatory disease.
- Skin infections and rosacea
- Respiratory infections caused by certain bacteria
- Malaria prevention: Travelers to malaria-prone areas sometimes take doxycycline as a preventive measure.
It also has FDA approval for rarer infections like Rocky Mountain spotted fever, cholera, plague, and anthrax exposure. Because so many bacterial strains respond to it, doctors often reach for doxycycline when they need a reliable, well-studied antibiotic.
How to Take It
Doxycycline is one of those medications where how you take it matters almost as much as whether you take it. The most important rule: don’t take it and immediately lie down. Doxycycline can irritate or even ulcerate your esophagus if the pill gets stuck on the way down. Take it with a full glass of water and stay sitting or standing for at least 30 minutes afterward. Taking it with a meal is the simplest way to avoid both esophageal irritation and the nausea that some people experience.
Unlike some older tetracycline antibiotics, doxycycline’s absorption isn’t dramatically reduced by food. If it bothers your stomach on an empty stomach, eating something alongside it is a reasonable trade-off. That said, calcium-rich foods like milk and yogurt, as well as antacids and iron supplements, can still interfere with absorption to some degree. Spacing these out from your dose by a couple of hours is a good habit.
Sun Sensitivity and Other Side Effects
The side effect that catches most people off guard is photosensitivity, an increased tendency to sunburn. In a large study of over 850 patients treated for Lyme disease, about 2% developed photosensitivity reactions ranging from itching and burning to noticeable redness on sun-exposed skin. The risk was higher in summer months (peaking at 4% in July) and roughly three times more common in women than men. Some earlier studies have reported rates as high as 15%, possibly depending on sun exposure habits and treatment duration.
If you’re taking doxycycline during warm months, wearing sunscreen and limiting direct sun exposure will reduce your risk significantly. Other common side effects include nausea, diarrhea, and upset stomach, which are typical of most antibiotics and usually manageable by taking the medication with food.
Who Should Avoid Doxycycline
Doxycycline belongs to the tetracycline class, and tetracyclines have a well-documented effect on developing teeth and bones. In children under 8, exposure can cause permanent yellowish-brown staining of both baby teeth and adult teeth. The discoloration depends on dose and duration, and after age 8, the tooth crowns are calcified enough that staining no longer occurs.
During pregnancy, tetracyclines are classified as potentially harmful. They’ve been associated with higher rates of certain birth defects, particularly during the second trimester, and can affect fetal bone development. Doxycycline specifically carries these warnings largely because of the broader tetracycline class data, and some researchers have argued the restrictions could be loosened for short courses (under 14 days) in the first half of pregnancy. But for now, it remains generally avoided during pregnancy, and doctors will typically choose an alternative antibiotic.
For children who need treatment for serious tick-borne infections like Rocky Mountain spotted fever, doxycycline is still used because the benefit outweighs the tooth-staining risk, especially for short courses. The CDC recommends it as first-line treatment for these conditions regardless of age.
How Long Treatment Typically Lasts
Treatment duration varies depending on what’s being treated. For early Lyme disease, the standard course is 10 to 14 days, with shorter courses preferred to reduce side effects and antibiotic resistance. For acne, courses tend to be longer, sometimes several weeks to a few months, though dermatologists generally aim to transition patients to topical treatments as soon as possible. For STI treatment, courses are often shorter, sometimes just 7 days. Malaria prevention requires taking doxycycline daily, starting before travel and continuing for 4 weeks after leaving a malaria-risk area.
Regardless of the condition, finishing the full prescribed course matters. Stopping early because you feel better can allow surviving bacteria to rebound, potentially making the infection harder to treat the second time around.