Can tetracycline and doxycycline be taken at the same time?

Question

The reason I would be taking both is rather complicated. Back in 2006 I fell, fracturing my back from T1 to T10.  They put two rods and eight pins in my back. That was Dec 06. In January 07 It became infected requiring a second emergency surgery. The infectious disease Dr's put me on doxycycline 100mg  x 2 daily and told me I would probably be taking it for life. Thus I am always on doxycycline. In the meantime, I also have severe emphysema and COPD, Which means I have to take a lot of antibiotics. On this lst go around, I have been on Biaxin, and omnicef. Neither has worked, I have taken tetracycline in the past, so I though maybe it was worth a try. However if there's no advantage to taking both then I guess it's a mute point. I do however appreciate your response.

Answer 1

I am not sure what the reason could be to take both.

Tetracycline and doxycycline are chemically related and have similar activity against most types of infections, so either one of the two would do the job just fine -- or neither one nor the combination of both would.

There are a few special cases where one is much more effective than the other (e.g. doxycycline is effective for malaria prophylaxis and tetracycline isn't). But then you still need just one of the two.

Answer 2

For most infections tetracycline and doxycycline have similar activity and specificity. There are rare exception when one works and the other doesn't, so it is conceivable that a mocroorganism resistant to doxycycline might response to tetracycline. However, this is unlikely and it appear wiser to try a select second antibiotic from another class. At a minimum you should discuss this with your doctor.