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.

01:36 Other medications like tigecycline are -- have a broad spectrum of antibiotic activity.

01:44 And they're often used when tetracycline resistance has developed.

01:48 We used it sometimes in MRSA and VRE as well.

01:51 We also use it in patients who have beta-lactamase producing bacterial infections, anaerobic infections, mycobacterial infections and chlamydia infections.

02:02 Remember that this particular medication is an intravenous use only.

02:06 So it is not used orally at all.

02:08 In terms of the toxicity of tetracyclines, first of all the GI symptoms.

02:15 And I think all tetracyclines are suspect with this.

02:18 They have common but minor side effects.

02:21 There is very rare episodes of life threatening enterocolitis.

02:25 But it's certainly there.

02:27 It does eliminate normal gut flora.

02:30 So you can be prone to that bacterial overgrowth syndrome and candidiasis.

02:35 Now fetal exposure to this medication results in dental enamel dysplasia.

02:41 This is a common exam question.

02:43 I do want you to remember this.

02:45 So tetracyclines with fetal exposure, dental enamel dysplasia.

02:51 In terms of other side effects you can get hepatotoxicity like most antibiotics.

02:56 Interestingly enough, you get Fanconi syndrome.

02:59 Which is a type of renal tubular acidosis.

03:01 Now these are in the outdated tetracyclines.

03:04 But this question still shows up on exams.

03:07 So Fanconi syndrome is associated with the tetracyclines.

03:11 Other side effects can include dizziness, vertigo and that's mostly with doxycycline.