From the Guidelines
Doxycycline has excellent bioavailability, with approximately 90-100% of the oral dose being absorbed into the bloodstream. This high bioavailability means that oral doxycycline is nearly as effective as intravenous administration, making it a convenient antibiotic choice for many infections.
Key Points
- Food can slightly decrease the rate but not the extent of absorption, so doxycycline can be taken with or without food.
- However, dairy products, antacids, iron supplements, and products containing calcium, magnesium, or aluminum can significantly reduce absorption by forming chelation complexes with the drug, so these should be taken at least 2 hours before or after doxycycline.
- The standard adult dosage is typically 100mg twice daily or 200mg once daily, with treatment duration varying based on the infection being treated, as seen in the treatment of Lyme disease where the recommended dosage is 100 mg twice per day 1.
- Doxycycline's high lipophilicity allows it to penetrate well into tissues, including the prostate, brain, and lungs, contributing to its effectiveness against various infections.
Considerations
- It is essential to note that while the provided evidence does not directly discuss the bioavailability of doxycycline, the recommended dosages and treatment guidelines imply its effectiveness when administered orally 1.
- The lack of direct information on bioavailability in the provided study highlights the importance of consulting a broader range of medical literature for comprehensive understanding.
- In clinical practice, the bioavailability of doxycycline is a critical factor in its efficacy against infections, and its high bioavailability supports its use as a first-line treatment for various conditions.
From the FDA Drug Label
Doxycycline is virtually completely absorbed after oral administration. The bioavailability of doxycycline is virtually complete after oral administration, as stated in the drug label 2.
- Key points:
- Absorption: Doxycycline is virtually completely absorbed after oral administration.
- Bioavailability: The label does not provide a specific percentage for bioavailability, but it is implied to be very high.
From the Research
Bioavailability of Doxycycline
The bioavailability of doxycycline, an antibiotic, has been studied in various formulations and under different conditions.
- The bioavailability of doxycycline can be affected by factors such as gastric pH and the presence of food, as shown in studies 3, 4.
- A study comparing the bioavailability of doxycycline monohydrate and doxycycline carrageenate found that the carrageenate formulation was not affected by prior administration of omeprazole, whereas the monohydrate showed a significant decrease in bioavailability 3.
- Another study found that a pelletised doxycycline product was bioequivalent to a reference product when taken without food, but the rate of absorption was affected by the presence of food 4.
- Several studies have compared the bioavailability of different doxycycline formulations, including capsules and tablets, and found them to be bioequivalent 5, 6, 7.
- The bioavailability of doxycycline has also been evaluated in healthy adult volunteers, with one study finding that a new capsule formulation was bioequivalent to the reference product 7.
Factors Affecting Bioavailability
- Gastric pH: The bioavailability of doxycycline can be affected by gastric pH, with decreased absorption at high gastric pH 3.
- Food: The presence of food can affect the rate of absorption of doxycycline, but not the extent of absorption 4.
- Formulation: Different formulations of doxycycline, such as capsules and tablets, can have similar bioavailability profiles 5, 6, 7.