Why prescribe sub-antimicrobial doses of oral antibiotics for anti-inflammation?

Question

Why do antibiotics like doxicillin work against acne? : askscience

Check the dose he's using. Dermatologists are starting to use subantimicrobial doses.

Some antibiotics have anti-inflammatory effects at lower doses. So for instance, you would take doxicillin at 200 mg for is anti biotic effect, but at 20 mg for iis anti inflammatory effect.

See

http://dermatologytimes.modernmedicine.com/dermatology-times/content/tags/acne-treatment/derms-slow-embrace-subantimicrobial-dose-concept

Why don't dermatologists prescribe anti-inflammatories, if they're not intending the antimicrobial purpose of oral antibiotics?

Subantimicrobial (low) Dose Doxycycline - antibiotics successful for moderate acne and rosacea without the resistant bacteria and changes to flora : scacjdiscussion

Curious if anyone else has tried a subantimicrobial dose (UNDER 50mg/day is considered subantimicrobial) of oral Doxycycline, prescribed to them of course. It seems the research shows that 40mg (2 x 20mg tablets) of doxycycline hyclate was just as effective as 100mg after 16 and 18 week trials, but with NO changes to the bacterial flora of the face and fewer side effects. So its method of action is different than high dose, but it’s still effective.

Answer 1

Tetracyclines such as doxycycline primarily work as antimicrobials by inhibiting protein synthesis in bacteria. However, these drugs can also act on eukaryotic cells like human immune cells, resulting in an anti-inflammatory effect that may require a lower dose. This may be part of the reason a sub-antimicrobial dosage is effective. A good summary here.

To the second point, there are alternatives to antimicrobials that target inflammation and other processes that contribute to acne; some are already in use and some are still being explored. Current guidelines in fact do recommend limiting oral antibiotic use when possible to avoid the emergence of resistant bacteria; however, there are cases when a regimen that includes an oral antibiotic is still currently the best treatment option.