Doxycycline vs. Tetracycline

Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

In this lesson, you're going to learn about some of the similarities and differences between two drugs. They are quite similar antibiotics called doxycycline and tetracycline.

Doxycycline vs. Tetracycline

They are part of the same drug class. They end in the same suffix. They are even used to treat many of the same things. They are two very similar drugs, but they do have their differences. They are antibiotics called doxycycline and tetracycline. Let's go over some of their similarities and differences in this lesson.

Names, Pharmacology, & Administration


Doxycycline is a drug that's found in numerous brand name medications, including Vibramycin and Adoxa. Similarly, tetracycline is a generic drug that can be found in the following brand name medications: Brodspec and Tetracap.


Both of these drugs target bacteria in a similar fashion. They inhibit bacterial protein synthesis by binding to two different ribosomal subunits: 30S and (possibly) 50S.

When taken orally, doxycycline is almost completely absorbed from the intestinal tract. Tetracycline is not far behind, upwards of 88% of this medication is absorbed from the intestinal tract.

It takes as little as 1.5 hours for peak concentrations to be reached in a person's serum after they've taken doxycycline (unless it's a delayed release tablet). Not far behind, tetracycline's peak serum levels are reached in as little as 2 hours after oral ingestion.

Both the drugs are distributed widely around the body, including into tissues and fluids, such as synovial (joint) fluid. However, both are poor at penetrating into the CSF, cerebrospinal fluid.


Tetracycline is usually taken on an empty stomach, about 1 hour prior to a meal or 2 hours after meals. It should also be taken 1-2 hours before or 4 hours after an antacid for maximum effectiveness.

Doxycycline can be similarly taken on an empty stomach, but if gastrointestinal irritation occurs, then it should be taken with food. You should note, however, that this may decrease the absorption of doxycycline by upwards of 20%.

Contraindications & Interactions


Neither drug should be taken if there is a known hypersensitivity to the drug, another ingredient in its dosage form, or any other antibiotic of the tetracycline class.

It's not recommended that these drugs be given to children under the age of 8, women who are breastfeeding, nor to pregnant women, especially those in the second or third trimester of pregnancy. That's because they can lead to defects in the formation of the child's teeth and skeleton.

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