Tetracycline

Tetracycline is a broad-spectrum antibiotic whose value in Ray Peat's framework extends far beyond its germicidal action, centering on its profound anti-inflammatory and respiratory-enhancing properties. Peat situated tetracycline within a family of quinone structures that spans from vitamin K to the anthraquinones found in cascara, all of which share the ability to stimulate mitochondrial respiration, reduce inflammation, and oppose fibrosis. 2 He noted that tetracycline directly blocks the enzyme responsible for nitric oxide production, a mechanism it shares with niacinamide, thereby interrupting a universal stress and injury signal. 5 This structural and functional kinship with endogenous quinones explains why Peat considered it not merely an antibiotic but a fundamental metabolic support, lamenting that its clinical neglect stems largely from the fact that it is too cheap to be profitably promoted. 2

The clinical application of tetracycline in Peat's work is highly context-dependent, with dosing varying from brief, high-intensity courses to longer, lower-dose regimens. For eliminating small intestine bacteria causing symptoms, Peat reported starting with 100 mg twice daily and seeing immediate results, while reserving double that dose for intense acute symptoms. 2 Danny Roddy has clarified that Peat's references to taking "one or two big doses" were often descriptions of his personal use, whereas for a legitimate infection, Peat consistently advised a course of two to three weeks and considered it paramount to finish the course. 10 Roddy also relayed Peat's caution that doses around 200 mg twice daily were for serious infections, suggesting that 250 mg capsules could be split to approximate a lower, safer dose. 4 A caller reported feeling "pretty bad" on tetracycline, which Roddy speculated might relate to a drop in blood sugar, a known effect he had experienced more severely with minocycline. 3

Peat drew a sharp distinction between tetracycline and its newer derivatives, doxycycline and minocycline, arguing that the older drug is safer. 1 Roddy has elaborated that the principal difference between these drugs is their absorption, with minocycline being absorbed far better than doxycycline, and doxycycline better than tetracycline, which accounts for the discrepancy in their effective doses. 8 However, this increased potency comes at a cost; Roddy noted that minocycline "seems the strongest" and appears to have the most side effects, an observation corroborated by Peat's acknowledgment that minocycline could cause some type of issue, possibly related to blood sugar dysregulation. 2 This reinforces the preference for the less absorbable, milder-acting tetracycline for modulating the intestinal environment.

Regarding the intestinal ecosystem, Peat rejected a simplistic division of bacteria into beneficial and harmful, arguing that the interactions are too complex. He pointed out that even supposedly beneficial lactobacillus species can make a germ-free animal susceptible to injury, and that the healthier a person is, the more sterile their small intestine is. 9 This aligns with the therapeutic goal of using tetracycline to reduce the overall bacterial burden in the small intestine, particularly the gram-negative bacteria that produce endotoxin. At the molecular level, Peat confirmed that the tetracyclines and macrolides like azithromycin are anti-inflammatory, and that even subantimicrobial doses are sufficient to lower prostaglandin synthesis and phospholipase A2, effects comparable to aspirin. 11 For topical applications, such as acne, Peat pragmatically suggested an over-the-counter neomycin lotion as the easiest alternative rather than a specific tetracycline formulation. 7