Some of you may be aware that the the antibiotic doxycycline hyclate has been found to possess anti-matrix metalloproteinase (MMP) activities. MMPs are the enzymes that break down connective tissue such as collagen, and their relative increase is thought to contribute to the development of wrinkles in aged skin.

This is because, while the ability to degrade the matrix is extremely important in growth and wound healing, if the processes of synthesis and degradation fall out of balance in favour of degradation, the overall amount of collagen will decrease.

In youth, these processes are in balance, but as we age, the degradative enzyme activity begins to overpower that of synthesis, leading to a loss of skin quality. Other factors that increase MMPs are photodamage and smoking.

In the past, I’ve boosted my skin’s balance in favour of collagen synthesis with isotretinoin, which worked beautifully but has drawbacks that in my opinion make it unacceptable for chronic use (cracking lips, sun sensitivity, etc.). I’ve also heard that the skin’s response to collagen-synthesis stimulating retinoids decreases with age.

So, in theory, one could boost its overall levels by instead interfering with the breakdown of collagen by inhibiting MMPs.

At present, the only MMP inhibitor that’s available readily and cheaply is doxycycline hyclate, an antibiotic often used to combat acne. Apparently, by taking a subantimicrobial dose (i.e., too little to kill bacteria) one can benefit from its anti-MMP activity while minimizing its side effects. Doxycycline is also used in this way in dentistry, where it is used to facilitate healing of the connective tissue in the gums.

There was also a study where doxycycline’s effect on wound healing was investigated because it was suspected it may *interfere* with normal wound healing as a side-effect, but it was instead found that the wounds actually healed either at the same rate or faster.

So, lately I’ve been noticing the accumulation with age and decades of intense sunlight a slight loss of skin elasticity (yes, wrinkles), so I decided to start taking 25mg/day doxycycline for a couple of months and see if this has any effect on the quality of my skin. I’ve taken some ‘before’ photos that highlight the problem, and I intend to compare these with pictures taken in 1 and 2 months to see if I can identify any change.

The literature is at first glance almost entirely free of this kind of experiment, with most papers focussing on doxycycline’s antibacterial and anti-inflammatory effects for the treatment of acne and rosacea. I’m sure there’s a good reason for this that I in my limited capacity don’t have time to dig up, so I’m pressing ahead regardless.

I’ll post the results, including before/after shots and analysis in about a month

Here’s some reading in the meantime:

• Inhibition of matrix metalloproteinases: a new skin care frontier
• Matrix metalloproteinases
• Doxycycline