Doxycycline vs. Bactrim – Complete Overview

With all the antibiotics available, it can be hard to tell the difference between them and which one might be best for you.

Two types of antibiotics are doxycycline and Bactrim. While they can both treat UTIs, the infections they treat are otherwise entirely different. Each antibiotic also works differently, which causes separate side effects and drug interactions.

For a complete overview of doxycycline and Bactrim, including their similarities and differences, continue reading.

Table of Contents

Are Bactrim and Doxycycline Hyclate the Same Thing?

While Bactrim and doxycycline Hyclate are both antibiotics, they are not the same. These two antibiotics belong to different classes, meaning their chemical structure and how they stop bacteria differ.

What is Bactrim?

Bactrim is the name brand of a combination antibiotic consisting of sulfamethoxazole and trimethoprim. It effectively treats many types of infections, but many people are allergic to it.

The two antibiotics included in Bactrim work together to stop a chemical that certain bacteria make to grow. By halting this chemical’s production, the bacteria can no longer grow and reproduce.

Bactrim is a combination of a sulfonamide, also known as a “sulfa” drug, and a folic acid inhibitor.

Some of the infections that Bactrim is used to treat include:

  • chronic bronchitis from bacteria flares
  • urinary tract infections
  • middle ear infections
  • traveler’s diarrhea
  • pertussis (whooping cough)

Bactrim is also used to prevent certain infections, such as pneumococcus in organ transplant recipients, Pneumocystis carinii pneumonia, and toxoplasma encephalitis in those with AIDS.

What Is Doxycycline?

Doxycycline is another type of antibiotic belonging to the class of tetracycline antibiotics. In addition to treating bacterial infections, it is also used to decrease inflammation from rosacea.

Doxycycline stops bacteria by binding to their ribosomal subunit, which prevents amino acids from being linked together and stops protein synthesis. Bacteria use these proteins to grow and reproduce, so when their creation is halted, they can no longer survive.

Some of the infections that doxycycline is used to treat include:

  • respiratory tract infections (from streptococcus pneumoniae, Haemophilus influenzae, or mycoplasma pneumoniae)
  • non-gonococcal urethritis
  • anthrax
  • typhus
  • chancroid
  • brucellosis
  • syphilis
  • cholera
  • rocky mountain spotted fever
  • acne
  • periodontal disease
  • rosacea
  • urinary tract infections
  • gonorrhea
  • actinomycosis
  • chlamydia
  • Lyme disease
  • Vincent’s infection

Doxycycline may also be used to prevent malaria.

Bactrim vs. Doxycycline

While Bactrim and doxycycline are both antibiotics, they are different types of medication and affect bacteria differently.

How Are Doxycycline and Bactrim Different?

The primary difference between doxycycline and Bactrim is the type of antibiotic that they are. Doxycycline is a tetracycline antibiotic, whereas Bactrim consists of a sulfa drug and a folic acid inhibitor.

These different classes mean that the two drugs attack bacteria differently, although the end goal of treating the infection is the same.

Doxycycline vs. Bactrim Side Effects

Doxycycline and Bactrim share common side effects, including stomach upset, vomiting, nausea, and loss of appetite.

Some other common side effects of doxycycline include:

  • weight loss
  • rash
  • hives
  • anemia
  • vaginal yeast infection

Other common side effects of Bactrim include:

  • painful or swollen tongue
  • spinning sensation
  • tiredness
  • ringing in the ears
  • insomnia

Some less common side effects of Bactrim include low blood sugar and severe diarrhea.

Many people who take Bactrim develop an allergic reaction. Contact your doctor immediately if you notice any signs of an allergic reaction, such as rash, hives, or swelling in the face while taking Bactrim.

Dosage of Bactrim vs. Doxycycline

A dosage of Bactrim typically consists of 800mg/160 mg sulfamethoxazole/trimethoprim and is taken orally every 12 hours. The course of antibiotics can last from 3 to 21 days, depending on what it treats or prevents.

Doxycycline comes in multiple forms, including tablets, delayed-release tablets, capsules, and liquid. It may be taken once or twice a day, usually for 7 to 14 days.

The average dose of doxycycline for adults is 200 mg on the first day of treatment (100 mg every 12 hours), then 100 to 200 mg each day following.

No matter which antibiotic you are prescribed, it is crucial to take it for the complete course as prescribed by your doctor—discontinuing your medication early or taking it for longer than prescribed can increase the risk of a subsequent infection or antibiotic resistance.

If you are experiencing severe side effects from Bactrim or doxycycline, it is important to discuss this with a doctor. Your doctor can help you safely discontinue the antibiotic and take another medication for your infection.

Warnings of Bactrim and Doxycycline

Both Bactrim and doxycycline can make your skin more sensitive to the sun. To protect yourself, be sure to use sunscreen, sunglasses, and protective clothing while taking these antibiotics.

Kidney stones may form in those who take Bactrim, and this risk increases if you do not drink enough water. To prevent kidney stones, drink a full glass of water whenever taking your antibiotic, and avoid beverages that increase the risk of dehydration, including alcohol and coffee.

Bactrim and doxycycline are also not safe for pregnant women to take, as it is known to harm unborn babies and potentially cause birth defects. Doxycycline can affect the development of bone in the fetus, while Bactrim may cause bilirubin to be displaced from proteins in the child’s blood, which can cause jaundice or kernicterus.

Those who become pregnant while taking Bactrim or doxycycline should discontinue the antibiotic immediately and talk to their healthcare provider. Additionally, these effects may still be passed to the child when breastfeeding, so they should also be avoided in mothers who choose to breastfeed.

Doxycycline and Bactrim Drug Interactions

Both Bactrim and doxycycline can interact with certain medications.

Bactrim may interact with:

  • cyclosporine
  • blood thinners
  • methotrexate
  • seizure medications
  • oral diabetes medications

Doxycycline may interact with:

  • penicillin
  • anticoagulants
  • bismuth subsalicylate
  • antacids (containing calcium, aluminum, or magnesium)
  • oral contraceptives
  • iron-containing preparations
  • methoxyflurane
  • carbamazepine
  • phenytoin

If you take any medications, but especially those listed above, it is important to disclose this information to your doctor.

Which Is Better, Bactrim or Doxycycline?

These two medications typically treat different infections, which means that the best medication will be the one that works on the infection you have.

It is also important to consider other health conditions that you have when determining which antibiotic would be best.

For example, those with the following health conditions should not take Bactrim:

  • kidney disease that is not monitored or treated
  • severe liver disease
  • a history of low platelets after taking any sulfa drug
  • anemia due to folic acid deficiency

Both doxycycline and Bactrim can also interact with other medications and supplements, so choosing the best one will consider what you are already taking.

Regarding the number of infections each medication can treat, the list for doxycycline is more extensive; however, the priority is still the infection you have. 

When to See a Doctor?

It is recommended to see a doctor whenever you suspect you have an infection. Some infections can become more severe infections if left untreated, so the sooner you start an antibiotic, the better for your health. 

Additionally, never take either of these antibiotics unless they have been prescribed to you. Taking someone else’s medication may result in severe side effects or an infection that has not been treated because the correct antibiotic was not taken.

When it comes to prescribing antibiotics, it is best to leave it to doctors who will weigh all factors to choose the best one.

Get Help from An Online Doctor

If you have an infection, an online doctor is a convenient way to discuss your symptoms and receive an antibiotic prescription.

For those who are curious about whether doxycycline or Bactrim would be better for their specific infection, your doctor can discuss the two antibiotics with consideration to the infection type, other medications you are taking, and preexisting health conditions.

Key Takeaways

Doxycycline and Bactrim are two antibiotics used to treat bacterial infections, although the way in which they accomplish this differs. Both antibiotics do not directly kill bacteria but instead, interfere with their methods of living and growing. Bactrim stops bacteria from producing a specific chemical, while doxycycline inhibits the synthesis of proteins; both of these actions make it so that bacteria can no longer function.

There are side effects associated with Bactrim and doxycycline, with some that they share including stomach upset, nausea, vomiting, and diarrhea. People are also very often allergic to Bactrim, which may cause the signs of an allergic reaction.

Both of these medications can interact with other medicines or may be unsafe to take in those with certain health conditions. Because of this, it is essential to disclose all this information to your healthcare provider to ensure that you are prescribed an antibiotic that is safe for you to take.


Content on the DrHouse website is written by our medical content team and reviewed by qualified MDs, PhDs, NPs, and PharmDs. We follow strict content creation guidelines to ensure accurate medical information. However, this content is for informational purposes only and not a substitute for professional medical advice, diagnosis, or treatment. For more information read our medical disclaimer.

Always consult with your physician or other qualified health providers about medical concerns. Never disregard professional medical advice or delay seeking it based on what you read on this website.

If you are experiencing high fever (>103F/39.4C), shortness of breath, difficulty breathing, chest pain, heart palpitations, abnormal bruising, abnormal bleeding, extreme fatigue, dizziness, new weakness or paralysis, difficulty with speech, confusion, extreme pain in any body part, or inability to remain hydrated or keep down fluids or feel you may have any other life-threatening condition, please go to the emergency department or call 911 immediately.



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