Doxycline is an antibiotic that is a member of the Tetracycline family of drugs. Like so many other bacteria, the tetracyclines come from a soil fungus and were discovered in the 1940’s. Or maybe it’s more accurate to say tetracyclines were rediscovered then because bone analysis of Nubian people who lived about 350AD show they ingested tetracycline likely in a locally brewed beer.
The tetracyclines work by binding to and deactivating the ribosomes inside the bacterial cell. Ribosomes are the bacteria’s protein factories, and without it they cannot produce the proteins they need to stay alive. Ribosomal deactivation happens in both gram positive and gram negative bacteria, though sometimes the antibiotic has a little more trouble getting into Gram positive cells with their thicker cell walls. Some bacteria have also developed resistance to the tetracyclines usually by developing a pump that spits the antibiotic out of the cell and thereby protecting the ribosomes on the inside.
As it treats a large number of bacteria, Doxycycline is considered a broad spectrum antibiotic. Doxycycline is the preferred agent in treating Chlamydia, Rickettsial infections spread by ticks (Typhus and Rocky Mountain Spotted Fever), and Cholera. It will also work against walking pneumonia (caused by Mycoplasma pneumonia, though technically Azithromycin is a better choice but there is no Fish-Azithro), most strains of Gonorrhea, and early Syphilis infections. Doxy will also work against Anthrax, Plague, Tularemia, and Legionnaires disease. While not FDA approved for this, it will also treat Lyme disease. It will also treat sinus infections, pneumonia, and ear infections, but it is generally a second or third line choice for these. Doxy is generally a poor choice for the streps and staph, as their thicker cell walls are harder to penetrate.
Unlike most antibiotics, Doxycycline is also active against certain parasites of the protozoal class. It can help prevent malaria and is often used as a prophylactic for people visiting malarial areas. However, it is poor in treating malaria once the disease is already established.
Doxycycline is best taken on an empty stomach, though it can be taken with foods as long as they don’t contain calcium (milk), iron (red meats), or aluminum or magnesium (antacids). Calcium, iron, aluminum, and magnesium bind to the antibiotic, decreasing its absorption. Doxycycline should not be taken by children under age 8 or by pregnant women, as it can cause staining of pre-emergent teeth. Unlike Tetracycline, expired Doxycycline does not cause kidney damage.
Trimethoprim-Sulfamethoxizole (a.k.a Bactrim, Septra, or co-trimoxazole and abreviated as TMP-SMX) is a combination of two different weaker antibiotics that when added together seem to be greater than the sum of their parts. Sulfamethoxizole is a sulfa-based antibiotic that works best against Gram-positive bacteria (like strep and staphs) as well as many anaerobic bacteria. Trimethoprim is a man-made antibiotic that works against aerobic bacteria. They are combined in a ratio of one part Trimethoprim to five parts sulfamethoxizole, so the dosing will often be listed as 80mg/400mg or 160mg/800mg. Both act by disrupting the bacteria’s ability to process folate, which stops DNA production and a host of other processes resulting in bacterial cell death.
TMP-SMX is considered a broad spectrum antibiotic. Trimethoprim-Sulfamethoxizole (TMP-SMX) is not a terribly effective antibiotic, and a lot of people have unpleasant reactions to its use. The worst case scenario is that TMP-SMX has a known risk of causing Stevens-Johnson Syndrome (SJS). SJS is a life-threatening reaction that causes your skin to peel off your body. Yeah, it’s as unpleasant as it sounds. Because of these problems, the use of TMP-SMX declined through the 80’s and in some countries it was even banned.
So why do we use it today? It’s four little letters– MRSA. As MRSA (Methycillin-Resistant Staph Aureus) began to spread across the world and began showing up in more and more infections, the medical community began looking for effective treatments. Doctors discovered there are two different types of MRSA. One is more common in hospital settings and is resistant to almost everything and can only be treated with IV antibiotics in the hospital. The other was termed community acquired Methycillin resistant Staph aureus (CA-MRSA) and only two oral antibiotics were found to kill it on a regular basis. These two antibiotics were TMP-SMX and Clindamycin. And so, TMP-SMX came roaring back into the medical mainstream.
While TMP-SMX is a broad spectrum antibiotic, cautious use is recommended due to the potential side effects and interactions with other medications. It is a first line agent for CA-MRSA. It is also considered first line for most all urinary tract infections, as it treats the top five causes of UTI’s (E.coli, proteus, klebsiella, enterobacter, and staph saprophyticus). It is also the first line agent for cat scratch disease. It will also treat most other streps and staphs, but other antibiotics will do the same with fewer side effects. It can be used for ear infections, pneumonia, chlamydia, ghonnorhea, toxoplasmosis, plague, cholera, travelers diarrhea, and many others. However, once again, there is usually a better choice. Interestingly, it does not do well against strep throat.
Because it can mess with your own folate metabolism, it should not be used in pregnancy.
Metronidazole (better known under its trade name, Flagyl) is a very interesting and unique antibiotic. Invented in France in the 1950’s, it is part of the Nitroimidazole family of antibiotics.
Metronidazole only works after being reduced (a chemistry term for “adding electrons”), and in the case of Metronidazole this reduction only occurs inside Anaerobic bacteria. Because of this, it is not toxic to human cells, which are aerobic. Once reduced, Metronidazole interferes with bacterial DNA replication, making the cell unable to reproduce or make needed proteins, resulting in cell death. Metronidazole is considered a broad-spectrum antibiotic.
As you likely figured out, Metronidazole is best against anaerobic bacteria. Most of your gut bacteria and STD’s are anaerobes, and so Metronidazole is a good choice for those infections. Metronidazole is also able to kill one of the most resistant bacteria in your gut– Clostridium difficile. Clostridium difficile (or C. diff, as it is often abbreviated) is thought to be present in the intestines of about 5% of the population. C. diff usually only causes a problem when all the other gut bacterial have been wiped out by another antibiotic, allowing C.diff to overgrow and cause problems. Metronidazole is one of only two antibiotics in common usage that will kill it.
Metronidazole is also interesting because it is one of the few antibacterial that also acts as an anti-protist and anti-helminthic. This means it can kill some parasites. In America, it is often used to treat Giardia lamblia (sometimes called Beaver Fever, due to its common presence in water that has been contaminated by beaver feces. Giardia is an anaerobic waterborne protozoa that causes abdominal pain, bloating, and fever with a watery diarrhea that can last for six weeks or longer). It is also used to treat Trichomonas vaginalis (a protozoa that is transmitted through sex and while rarely affecting men can cause a frothy greenish fishy smelling vaginal discharge in women), and Entamoeba histolytica (an anaerobic protozoa of the Amoeba family that causes amoebic dysentery and amoebic liver abscesses).
Metronidazole is generally considered the first line drug for the protozoal infections noted above, C. diff colitis, and infections suspected to be caused by anaerobes (dental abscesses, pelvic inflammatory disease, bacterial vaginosis, aspiration pneumonia, intra-abdominal infections, lung abscesses, stomach ulcers caused by the bacteria Heliobacter pylori, and tetanus. It is a poor choice for treatment of streps and staphs, as they are both aerobic bacteria. Metronidazole penetrates the blood-brain barrier better than any other antibiotic and so is a good choice for meningitis caused by anaerobic bacteria. (Unfortunately, most meningitis cases are caused by aerobes.)
Side effects are common, and many complain of belly aches or a metallic taste in their mouth while taking this drug. You should also not drink alcohol while on this drug, as it interferes with your body’s ability to metabolize alcohol and will give you an unpleasant though harmless reaction.
Clindamycin  is a member of the lincosamide family of antibiotics, which were isolated from a member of the Streptomyces bacteria family.
Clindamycin works by binding to the ribosome (protein factory) of the bacteria making the bacteria unable to produce the proteins it needs to stay alive.
Clindamycin is a very broad-spectrum antibiotic able to kill a wide variety of both aerobic gram positive (streps and staphs) and anaerobic gram negative bacteria, but gram negative aerobes (like C. diff) are resistant. While resistance to Clinda is rare, it is increasing. Most strains of CA-MRSA are killed by Clinda, but resistance becomes more common the farther west you travel in the USA.
Clindamycin is the antibiotic most often associated with the development of C. diff colitis. Clinda does not kill C. diff but does kill all its competition, allowing it to overgrow, which leads to illness. C. diff colitis presents as abdominal pain, initial watery stools that eventually can become bloody, fevers that can reach 105 degrees, and stools that smell like horse manure. There will almost always be a history of the person having recently taken a broad spectrum antibiotic. Imodium will significantly worsen the symptoms. Treatment is with Metronidazole or a fecal transplant. (Google that, if you dare.)
Clinda is considered a first line agent for skin and soft tissue infections (streps and staphs), pelvic infections, intra-abdominal infections (like peritonitis and diverticulitis), lung infections caused by Strep pneumo (lung abscesses, pneumonia, and empyema), bacterial vaginosis, and CA-MRSA.
A Word On Medication Allergies
Medication allergies are something we constantly worry about in the medical community. Lots of people claim to be allergic to this antibiotic or that antibiotic. The antibiotics people are most often allergic to are the penicillins and the sulfa family of antibiotics. Now I understand some people have very significant and real allergies; if you have had hives or other signs of anaphylaxis, you are likely allergic to the antibiotic you had taken just prior to the reaction.
However, many people think they have an allergy because they had a more minor reaction while taking the antibiotic. I can’t tell you how many patients I have seen who think they are allergic because they had a rash when they were three years old or the antibiotic upset their stomach one time. This was probably just a non-allergic side effect of the antibiotic or the illness and not a true allergy. An interesting study was recently performed at the Mayo Clinic in Florida. Three hundred eighty-four people with self-reported penicillin allergy had penicillin allergy testing performed. Guess what? Of those, 94% were negative.
In the modern medical world, allergies to an antibiotic are not that big a deal. There are lots of alternative antibiotics we can use if you are allergic. “Allergic to penicillin? Fine. We’ll use a cephalosporin. Allergic to that, too?! Fine. We will use something else.” However, in a post-apocalyptic scenario, the only antibiotic you may be able to get may be the one you have always thought you were allergic to. Will you take it? It probably depends on how ill you are and how bad the reaction you had to the antibiotic was.
Might I suggest that those of you who think you have an allergy to an antibiotic go see your doctor and have an allergy test BEFORE the SHTF. Then you will know what you are really allergic to and what you aren’t.