Tetracyclines – Bacterial Protein Synthesis Inhibitors (Antibiotics)

00:00 Let's move on to the tetracyclines.

00:03 Now tetracyclines are very commonly used.

00:05 They are broad spectrum bacteriostatic medications that are used mostly orally.

00:10 They work both through gram positive and gram negative bacteria.

00:15 And they may actually work with some protozoan as well.

00:19 There's widespread resistance with two big major mechanisms.

00:24 The first one is through a development of an efflux pump.

00:27 And that's often seen in the porteus and the pseudomonas species.

00:33 And in fact porteus and pseudomonas are quite interesting because they have multidrug pumps.

00:38 So they actually have these pumps that will eject the whole host of different medications.

00:42 And the second mechanism of resistance is through ribosomal protection proteins that actually prevent binding.

00:48 Almost like a little shield around the ribosome.

00:51 The prototypical drug in the tetracycline family is actually doxycycline or tetracycline.

00:59 Doxycycline is used long term in acne treatment.

01:03 It has a very long duration of activity.

01:07 And it's relatively non-toxic.

01:09 It's also used in bronchitis, bronchitis prevention and leptospirosis.

01:14 Minocycline is used almost exclusively in acne.

01:18 Demeclocycline is useful in most infectious diseases.

01:22 And also has a bit of a diuretic effect.

01:25 So if you go back to hormonal lectures and the adrenal lectures that we've spoken about, you will see that we have talked about demeclocycline and antidiuretic hormones secreting tumors.

01:37 In terms of the toxicity of tetracyclines.

01:40 First of all GI symptoms and I think all tetracyclines are suspect with this.

01:46 They have common but minor side effects, there is very rare episodes of life-threatening enterocolitis, but, it's certainly there.

01:54 It does eliminate normal gut flora, so, you can be prone to bacterial overgrowth syndrome and candidiasis.

02:03 Now, fetal exposure to this medication, results in dental enamel dysplasia.

02:08 This is a common exam question, i do want you to remember this.

02:12 So tetracyclines with fetal exposure, dental enamel dysplasia.

02:19 In terms of other side effects, you can get hepatotoxicity, like most antibiotics, dizziness, vertigo and that's mostly with doxycycline.