Doryx (Doxycycline): Uses, Side Effects, Dosage

By Terez Malka, MD
Medically reviewed checkmarkMedically reviewed
December 29, 2021

Doryx is a brand name for doxycycline, a common antibiotic used to treat several different kinds of bacterial infections, acne, and more. 

In this article, I’ll tell you more about Doryx, why it’s used, its common side effects, dosage, and common risks associated with the medication.

I’ll also list some foods, medications, and behaviors to avoid when taking Doryx.

What is Doryx?

Doryx is a tetracycline antibiotic. It’s a brand name of doxycycline, a type of drug used to treat a variety of infections caused by bacteria.

Doryx may also be used for anti-inflammatory purposes, such as in the treatment of some autoimmune diseases.

Doryx works by keeping bacteria from multiplying, which allows your immune system to fight off the infection.

Doryx can be prescribed for skin infections, bacterial respiratory infections, urinary tract infections, periodontal infections (gum disease), respiratory bacterial illness, eye infections, acne, and rosacea.

It can also be used for the prevention and treatment of malaria and sexually transmitted infections.

Doryx is only available with a prescription.

It may be prescribed in time release tablets, which should not be crushed or split.

If you cannot swallow pills, let your medical provider know.

It’s important to follow the instructions on how often to take Doryx.

Be sure to complete the full course of your prescribed antibiotics.

If you don’t, your bacterial infection may not resolve fully and may develop resistance to antibiotics, leading to more severe infections in the future that are more difficult to treat.

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Doryx Uses

Doryx is used to treat many conditions.

Your doctor or healthcare provider may prescribe it for one of many FDA-approved reasons, or may use it off-label if they believe that it is the right treatment for your health needs.

If you have questions about why your doctor prescribed Doryx, be sure to speak with your healthcare provider or pharmacist.


The skin has its own microbiome—a layer of bacteria.

While there are many types of bacteria that live there normally and don’t cause problems, or are even helpful, sometimes certain bacteria can contribute to skin problems like acne or rosacea.

Doryx or other tetracyclines are commonly used in the treatment of acne and other skin conditions caused or made worse by bacteria.

Antibiotics for severe acne won’t work overnight.

A dermatologist or other provider may prescribe Doryx for a few weeks or a few months, depending on your condition.

Doryx won’t work immediately, but most may start to see results within two weeks.

It may be used for up to three months when addressing skin infections.

Urinary tract infections

Doryx may be used for some urinary tract infections (UTIs) that do not respond to other antibiotics, or if you have allergies to other antibiotics.

Your healthcare provider will run a urine culture test to determine if it is an effective antibiotic for your infection. 

Intestinal infections

Almost all food poisoning and stomach flu in the US is caused by viruses, not bacteria, and antibiotics are not helpful. 

But if your provider determines your symptoms are caused by bacteria, Doryx and other tetracycline antibiotics may be used to treat some infections of the gastrointestinal tract.

Respiratory infections

Viral illnesses like colds or the flu won’t respond to antibiotics, and taking them may even make symptoms worse.

But some types of respiratory illness can be caused or complicated by bacteria.

Bacterial sinusitis, bacterial pneumonia, and some forms of bacterial bronchitis can be effectively treated with Doryx.

Eye infections

Most eye infections are viral, but you should speak with a healthcare provider to make sure. 

If bacterial infections are left untreated, permanent damage—and even blindness—can occur. 

Most eye infections can be treated with antibiotic eye drops or ointment, but some more severe infections may require an oral antibiotic.

Doryx may be able to treat bacteria that have infected the eye while also working to prevent scarring thanks to its anti-inflammatory properties.

It may also treat sexually transmitted infections, like chlamydial conjunctivitis, that can infect the eyes.

Sexually transmitted infections (STIs)

Doryx is FDA-approved for treating certain bacterial sexually transmitted infections, including:

Doryx may also be prescribed preventively if there is a risk for STIs.

Periodontitis (gum disease)

Gum disease is common, and can impact your overall health.

There are many healthy and beneficial bacteria that live in the mouth but an overgrowth of the wrong kind of bacteria can wreak havoc on the delicate tissue of the gums.

Doryx may be prescribed to treat periodontitis, which can result in swollen or bleeding gums, constant bad breath, and pain when chewing.

Doxycycline (Doryx) works to decrease the unhealthy bacteria in your mouth.


Malaria is a serious, sometimes fatal disease that is spread by mosquitoes.

Prevention is important, and Doryx may be used to protect against malaria during travel in high-risk regions.

It can also be used to treat malaria when paired with other drugs, like quinine.

Doryx Side Effects

Like other antibiotics, Doryx has some common and typically mild side effects:

Talk to your doctor if you have concerns about the side effects that you are experiencing.

In rare cases, Doryx may cause more severe side effects:

Doryx should not be used in children under 8 years of age, because it can have permanent staining effects on teeth and may also impact growth and development.

It should not be used during pregnancy or lactation.

Anyone allergic to tetracycline antibiotics should not take Doryx.

If adverse reactions occur, speak with your doctor right away.

How to Take Doryx

Dosage and administration

Doryx may be prescribed in different doses.

Common Doryx doses include 50 mg tablets and 200 mg capsules.

Make sure to follow the instructions on your prescription.

Talk to your healthcare provider or pharmacist about any other medications and supplements you are taking before starting Doryx.

Drink plenty of water or fluids when you take Doryx and throughout the day.

What happens if I miss a dose?

If you miss a dose of Doryx, first determine how long ago you should have taken it.

If you are close to your next dose, take it as regularly scheduled.

Do not double up on doses of Doryx.

If you have questions about the timing of your doses, ask your healthcare provider or pharmacist.

What happens if I take too much?

It’s important not to take too much Doryx.

If you do, seek immediate medical help. Call Poison Control at 1-800-222-1222 for guidance.

If you are having severe symptoms after taking too much medication, visit an ER.

If you are with someone who has taken too much Doryx and they are having trouble breathing, are unconscious, or are having seizures, call 9-1-1.

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What to Avoid While Taking Doryx

Doryx may interact with many other drugs.

Some common drug interactions include the following medicines:

  • Anticoagulants (blood thinners)
  • Penicillin
  • Antacids
  • Iron
  • Magnesium
  • Oral contraceptives
  • Anti-epileptics

Your doctor and pharmacist will make sure that your medications work together and do not interact.

Tell them about all supplements and OTC drugs that you take, like antacids or pain relievers.

It’s essential to stay hydrated while you take Doryx.

Take each dose with a full glass of water. Drink more throughout the day so your hydration needs are met.

Don’t take Doryx with milk, yogurt, or other dairy products.

They may prevent proper absorption or affect how the dosage works.

You can consume them a few hours before or after you take your dose.

Most medical advice will recommend avoiding alcohol while on antibiotics.

Alcohol may make Doryx less effective at treating your infection.

Doryx can increase your risk of sunburn.

Don’t spend too much time in the sun or use tanning beds. If you do need to be in the sun, wear sunscreen and proper protective clothing.

How K Health Can Help

Have questions about your health or why you were prescribed Doryx? You can connect with a primary care provider in the K Health app.

Download K Health to check your symptoms, explore conditions and treatments, and if needed text with a provider in minutes. K Health’s AI-powered app is based on 20 years of clinical data.

Frequently Asked Questions

What are Doryx capsules used for?
Doryx can be used to treat many conditions: acne, STIs, eye infections, bacterial respiratory illness, urinary tract infections, and more. It is sometimes used in patients who are being treated for anthrax exposure. It may also be used for tick-borne illnesses like Lyme disease and Rocky Mountain Spotted Fever. It may also be used to prevent or treat malaria.
Are Doryx and doxycycline the same?
Yes. Doryx is a brand name of doxycycline. Some forms of doxycycline may differ in inactive ingredients or dosage, but both brand-name or generic doxycycline should be equally effective at treating infections.
Is doxycycline a powerful antibiotic?
Yes. Doryx is an antibiotic that can be effective at treating resistant infections. Its potency is determined by dosage and course of treatment, and if it is appropriate for your specific infection. Your doctor can help you figure out if doxycycline or Doryx is an appropriate choice for your condition.
How long does Doryx take to work?
The time that Doryx takes to work depends on the reason you are taking it and the dosage you are on. For acne, it may take up to two weeks before you notice improvements. For most bacterial illnesses, you should notice improvements within a few days. If at any time you feel worse, speak to your doctor.
K Health articles are all written and reviewed by MDs, PhDs, NPs, or PharmDs and are for informational purposes only. This information does not constitute and should not be relied on for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment.

K Health has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical associations. We avoid using tertiary references.

Terez Malka, MD

Dr. Terez Malka is a board-certified pediatrician and emergency medicine physician.

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