Medications and the Microbiota
From antibiotics to acid blockers to metformin, chronic medications reshape your microbiome to differing degrees, and this chapter shows what you can safely do about the side effects without ever stopping prescribed treatment on your own.
Chapter 7 is a clinical-pragmatic overview. If you take chronic medication — or are considering one — you'll find here how it affects your microbiome and what can be done safely.
One rule above all: never discontinue a prescribed medication on your own initiative for microbiome reasons. Treatment of the underlying disease is the priority. What's here is the scientific background for adjuncts (with treating physician's approval) and side-effect management.
Most drugs affect the microbiome to some extent — Maier et al. 2018 Nature screened ~1000 human drugs in vitro, and 24% inhibited growth of at least one gut bacterial species. [229] Clinical relevance: antibiotics have the most dramatic effect; chronic PPIs cause meaningful dysbiosis; metformin acts partly via the microbiome; NSAIDs trigger gut barrier damage. The recovery mechanism and the time it requires depend on the drug's indication and the duration of use.
Antibiotics
Antibiotics are simultaneously the most effective and most destructive microbiome-level interventions in medicine: within a few days they can drive a 20–40% diversity drop unlike any other drug class. The clinical decision is therefore never "antibiotic versus microbiome" — it is one of necessity and spectrum narrowing. The subsections below cover how a course shifts species composition, how long the system takes to recover, and what you can do to reduce collateral damage.
Effect mechanism on the microbiota
By antibiotic spectrum:
- Narrow spectrum (e.g., penicillin V, clindamycin) — targeted, less collateral damage
- Broad spectrum (e.g., amoxicillin/clavulanate, cephalosporins, fluoroquinolones) — wider microbiome shift
- Anaerobe-specific (e.g., metronidazole, clindamycin) — destroys especially the obligate anaerobes of the colon, the main C. difficile overgrowth risk factor
The effect is immediate: measurable within 24–48 hours. After a 7-day amoxicillin course, microbial diversity drops 20–40%; full recovery time varies by individual.
Recovery timeline
| Phase | What happens | What to do |
|---|---|---|
| Acute (0–14 days) | Significant diversity loss, inflammatory species dominate | Don't take a probiotic together with the AB; increased hydration; plenty of fiber (if tolerated) |
| Early recovery (2–6 weeks) | 70–85% of microbiome returns | Continue fermented foods, prebiotics; reduce stress |
| Late recovery (3+ months) | Some species absent or returned at different ratio | Long-term diversity maintenance (chapter 4); second AB course only if justified |
| 1+ year | Some species never fully return, especially after childhood AB | Talk to your doctors about maintenance strategy |
The classic Dethlefsen & Relman 2011 PNAS study measured microbiomes 6 months after 2 ciprofloxacin courses in 3 adults: most species returned, but certain taxa permanently disappeared. [218] Clinical relevance: childhood AB exposure has longer-term consequences (allergy, atopy, asthma risk), especially 0–24 months. [599] This doesn't mean withhold AB when indicated — it means avoiding unnecessary AB is valuable.
Probiotic support during antibiotics
Chapters 3 and 11 detail: S. boulardii CNCM I-745 (500 mg/day) and L. rhamnosus GG (10⁹–10¹⁰ CFU/day) are evidence-based choices for AAD prevention. Timing: start with day 1 of AB, continue +3 days after. This is the current scientific consensus; that said, more and more questions are being raised about combining probiotics with antibiotics and about probiotics' possible tendency to predispose to long-term dysbiosis.
A probiotic taken alongside the AB does not reduce the AB's effectiveness against the target infection (the probiotic strain acts in the gut, not at the infection site) — a common misconception.
Proton pump inhibitors (PPIs)
PPIs are among the most over-prescribed drugs in medicine: prescription durations frequently stretch into the decade range long after the original indication has resolved. Microbiome-wise this matters because gastric acid is not only a digestive aid — it is also a barrier that selects against swallowed bacteria. Chronically suppressing that barrier causes meaningful upper-GI shifts, increased C. difficile susceptibility, and nutrient absorption problems. The following subsections unpack these mechanisms, the clinical consequences, and the logic of deprescribing.
Mechanism
PPIs (omeprazole, pantoprazole, esomeprazole, etc.) strongly suppress gastric acid production. But gastric acid is a natural barrier protecting the rest of the gut from swallowed bacteria. When this barrier weakens, two things happen:
- Upper GI microbial overgrowth — oral and gastric flora can appear in the small intestine
- Increased C. difficile and Salmonella susceptibility — swallowed pathogens get through
Clinical consequences
Imhann et al. 2016 Gut — large Dutch cohort: PPI users' microbiomes significantly differ from non-users, with Streptococcaceae and upper-GI species enrichment. [600] Multiple cohort studies (CDC, US; meta-analyses) consistently show 1.3–2× increase in C. difficile, pneumonia, and fracture risk with long-term use.
When necessary, when worth tapering?
Necessary indications (including long-term):
- Severe GERD (Los Angeles C/D grade)
- Barrett's esophagus
- Active gastric or duodenal ulcer
- H. pylori eradication (short-term)
- NSAID-related gastroprotection (in high-risk patients)
Often unnecessarily, or long-term-prescribed:
- Mild-moderate GERD symptoms instead of lifestyle modification
- "Prevention" in low-risk patients
- Courses started without indication and never stopped
How to taper (only under medical supervision):
- Gradual reduction (not abrupt stop — rebound acid production)
- H2-blocker transition (famotidine) often helps
- Lifestyle: weight loss, meal timing (last meal 3+ hours before bed), reduction of triggers (coffee, spicy, alcohol, chocolate)
- Sleep position: left side, raised head of bed
AGA Best Practice Advice 2022 (Targownik et al.) provides a concrete PPI deprescribing protocol: annual review for every chronic PPI user, discussion of indication and maintenance need. [601] M.D. note (Munar): PPI rebound (acid hypersecretion after stopping) can last 2–4 weeks — this doesn't mean "PPI is needed," it means the wean is structured.
NSAIDs
Non-steroidal anti-inflammatories (ibuprofen, naproxen, diclofenac, aspirin) cause gut barrier damage via multiple mechanisms: COX-1 inhibition → reduced prostaglandin production → small bowel mucosal inflammation (NSAID enteropathy), plus microbiome dysbiosis.
What does this mean in practice?
- Occasional NSAID (1–2 times/week) → minimal consequence
- Chronic daily NSAID (e.g., chronic pain, athletic injury management) → meaningful risk
- High-dose aspirin (cardiovascular protection 81 mg/day is not high, but occasionally 325 mg daily) → GI bleeding risk
What can be done?
- Consider alternatives: acetaminophen (paracetamol) for chronic pain has lower GI risk; topical NSAID (gel, cream) avoids systemic absorption
- PPI protection in high-risk patients (elderly, ulcer history, chronic NSAID + anticoagulant)
- Microbiome support during chronic NSAID use: increased fiber, probiotic consideration (clinical evidence building), and FMT in severe dysbiosis
Metformin
Metformin is first-line T2DM treatment — and interestingly, its effectiveness is partly mediated through the microbiome. Forslund et al. 2015 Nature showed: some of the microbiome differences observed in T2DM patients are actually metformin effects, not disease effects. [222]
What does metformin do to the microbiome?
- Increases Akkermansia muciniphila proportion (favorable)
- Shifts the SCFA-producing profile
- Decreases Bacteroides fragilis (affecting bile acid metabolism)
Microbiome explanation for classic side effects (diarrhea, bloating): the change is an initial adaptation phase. Gradual dose escalation (250 mg → 500 mg → 1000 mg) significantly reduces it. Extended-release (XR) formulation is also better tolerated.
B12 deficiency: chronic metformin causes it in 10–30%, partly microbiome-mediated. Annual B12 level check recommended.
GLP-1 receptor agonists (Ozempic, Wegovy, Mounjaro)
Semaglutide (Ozempic, Wegovy) and tirzepatide (Mounjaro) are the fastest-spreading drugs for type 2 diabetes and obesity. GLP-1 (glucagon-like peptide-1) is a gut hormone secreted by intestinal L-cells in response to eating: it slows gastric emptying, enhances the insulin response, and reduces appetite. These drugs mimic that hormone.
What's the microbiome link? ( open) In two directions. First, the gut bacteria's fiber-fermentation "by-product" (butyrate and other SCFAs) naturally stimulates your own GLP-1 production — so a fiber-rich diet is the "soft" counterpart of the drug on this axis. Second, early (largely animal) data suggest part of semaglutide's metabolic effect may also act through changes to the gut microbiome. [2717] Human evidence for the latter is still weak — treat it as a hypothesis.
Muscle protection. 25–40% of the weight lost on GLP-1 agonists can be muscle mass. That's why protein intake (1.2–1.6 g/kg/day) and resistance training are not optional but an integral part of treatment.
Side effects. Most common are GI complaints (nausea, bloating, constipation) — often transient and eased by gradual dose escalation. The slowed gut motility can also shift microbiome composition.
Starting, dosing, and stopping the drug is always the physician's call — this chapter provides background, not a prescription.
GLP-1 drugs owe their existence to a venomous lizard. In the 1980s a researcher was curious how the Gila monster (Heloderma suspectum) can eat only a few times a year. In 1992, John Eng isolated a peptide from its venom (exendin-4) that resembles human GLP-1 but — as a fortunate "accident" — resists rapid breakdown, so it acts for hours. [2715] This became the first GLP-1 agonist (exenatide, 2005), and later today's semaglutide and tirzepatide. [2716]
Antipsychotics
Second-generation antipsychotics (olanzapine, quetiapine, clozapine, risperidone) have metabolic syndrome and weight gain as prominent side effects. The mechanism is partly microbiome-mediated — animal studies and small human studies show Firmicutes shifts and LPS elevation.
What can be done (while maintaining treatment)?
- Dietary awareness (especially carbohydrate intake)
- Movement (challenging for many patients, but meaningful)
- Annual metabolic panel review (HbA1c, lipids, BMI, waist circumference)
- Probiotic or prebiotic experimentally — discuss with the psychiatrist
Drug discontinuation is never an option on patient self-initiative — disease recurrence is far worse than the side effect.
Hormonal agents
The relationship between sex hormones and the microbiome runs in both directions: estrogen and progesterone levels influence species composition (especially Lactobacillus dominance in the vaginal microbiome and the activity of β-glucuronidase-producing colonic bacteria), while the microbiome itself participates in estrogen recycling — the so-called estrobolome. Hormonal therapies tilt this balance — generally less dramatically than antibiotics, but with clinically measurable effects under long-term use. The subsections below cover oral contraceptives, hormone replacement therapy, and drugs affecting the androgen axis.
Oral contraceptives and HRT
The estrogen-microbiome link ("estrobolome") is an interesting area of recent years. Intestinal estrogen reabsorption is regulated by microbial β-glucuronidase activity — meaning your microbiome influences your estrogen level and vice versa. [605]
Clinical relevance:
- Oral contraceptive use can cause meaningful microbiome shifts, but usually not at clinically significant magnitude
- HRT (post-menopause hormone replacement) longer-term microbiome effects under investigation
- In IBD patients, contraceptive use carries modestly elevated activity risk — discuss with treating physicians
Hormone replacement elsewhere
Thyroid hormone (levothyroxine) absorption can be affected by gut microbiome signature; this explains why some patients appear "dose-resistant."
Chemotherapy
Chemotherapy has enormous effects on both the gut mucosa (mucositis) and the microbiome. Two directions:
Side-effect reduction: probiotic support (LGG, S. boulardii) for chemotherapy-associated mucositis and diarrhea — limited but existing evidence. AGA 2020 recommendation is cautious: only in immunocompetent patients, decided by the treating oncologist. FMT support is in the experimental phase.
Oncology response predictor: see chapter 3 — checkpoint inhibitor therapy effectiveness is affected by microbiome signature. Clinical implication in oncology care: avoid unnecessary AB during chemo.
Pre- and post-chemo microbiome signature measurement is currently research-level; the Vetizou et al. 2015 Science foundational work has built the evidence base. [28] In clinical practice: prolonged antibiotic use during chemo worsens outcomes — discuss with the treating oncologist.
Other important drug groups (brief overview)
- Antidepressants (SSRIs): serotonin mediation is partly microbiome-related; chronic use mildly affects serotonin-producing microbial species
- Statins: small microbiome shifts, low clinical relevance
- Antihypertensives (ACEi, ARBs, calcium channel blockers): variable and small microbiome effects
- Bisphosphonates (osteoporosis): GI side effects are gut-microbiome relevant
Relevant supplements and vitamins from a microbiome perspective
The vitamin and supplement market is huge, and most products' microbiome effect is overstated. The brief overview below focuses on where there is meaningful evidence.
Vitamin D. Well-known modulator of gut mucosal immune function and gut barrier integrity. Most European adults are at subclinically insufficient levels by late winter. Clinical deep-dive: 2000 IU/day supplementation October–March is usually enough; higher dose or year-round use is guided by serum level measurement but, except in a few specific cases, is not recommended. From microbiome perspective, Faecalibacterium prausnitzii and other butyrate producers show abundance-positive correlation with adequate vitamin D level. [560]
Vitamin B12 (cobalamin). Some gut bacteria produce B12, but this is not absorbed in the small intestine (not accessible from the colon). Vegan/vegetarian diet and chronic PPI, metformin users are prone to B12 deficiency. Indication for supplementation: blood level measurement + lifestyle/pharmacological risk. Form: cyanocobalamin or methylcobalamin.
Omega-3 fatty acids (EPA + DHA). Anti-inflammatory effect, indirect microbiome benefit via gut barrier integrity and SCFA production support. Clinical deep-dive: 1–2 g EPA+DHA/day documented to reduce IBD activity and depressive symptoms; microbiome shift measurable within 8 weeks (more Bifidobacterium, Roseburia). Marine (fish oil) or algae-based form. [122]
Magnesium. Magnesium deficiency is common and can lead to gut motility problems, muscle cramps, sleep disturbance. Magnesium bisglycinate form is well tolerated, magnesium oxide tends to cause diarrhea (can be useful as side effect for constipation). Microbiome effect indirect — via gut motility improvement.
Vitamin K2 (menaquinone, MK-7). Colonic bacteria produce part of vitamin K; K2 deficiency may be suspected after long antibiotic courses. Due to bone and vascular effects, natural dietary sources (natto, hard cheeses) or MK-7 supplement are good forms.
Inulin, FOS, GOS (prebiotic fibers as supplements). See chapter 4 — obtainable from diet, as supplement 5–10 g/day is the starting dose. PHGG (partially hydrolyzed guar gum) is often better tolerated by IBS patients than inulin.
What not to take with a "microbiome-boosting" label:
- "Detox" packages, colon cleansing teas — no evidence, can cause harm
- High-dose vitamin mega-complex (without deficiency measurement) — money waste or hyperdose toxicity
- Generic "gut-friendly" multi-strain probiotic without strain designation (see chapter 11 detailed table)
- "Cell-renewing" or "epigenetic" premium packages — marketing price
Surgical context — medications in the perioperative period
Before and after surgery, several medication changes often happen, and the microbiome effect doesn't always reach the planning table. Some common considerations:
Prophylactic antibiotic. As part of surgical protocol, 1 dose (or 24-hour) AB prophylaxis is recommended before almost every surgical procedure. This is warranted, but the microbiome effect (transient diversity decrease, C. difficile risk) is realistically accountable. S. boulardii co-administration to reduce diarrhea risk is considerable — coordinated with surgeon.
PPI in the perioperative period. Stress ulcer prevention is justified during ICU stay. Continuation beyond 4–8 weeks post-op is to be re-evaluated — patients often stay on PPI longer than necessary. GP follow-up review is warranted.
Opioids and gut motility. Postoperative opioid use (even for 24–72 hours) causes gut paralysis; this through microbiome shift can leave prolonged diarrhea, constipation, SIBO risk. Goal: switch to non-opioid analgesia as early as possible.
Bariatric surgery special considerations. After gastric bypass and sleeve gastrectomy, the microbiome transforms long-term (up to 1–2 years). Vitamin and mineral supplementation is mandatory (B12, D, iron, calcium), and the bariatric surgical dietitian's protocol is the leading guide.
Colorectal surgery. Colon segment resection changes microbiome function. Postoperative nutritional rehabilitation and probiotic supplementation are decided by the surgical team. After IBD surgery, VSL#3 / De Simone formula is evidence-based for pouchitis prevention (chapter 11).
Perioperative microbiome management is not yet standard clinical practice, but three principles protect the patient:
- Indication-driven AB prophylaxis: only per protocol, only as long as needed
- PPI tapering within 4–8 weeks if no active indication remains
- Early mobilization and normal nutrition protocol as soon as surgical status allows — long fasting rapidly worsens microbiome diversity [634]
What you can do tomorrow
- Antibiotic course: ask your doctor whether it's truly needed (don't decide yourself). If yes, S. boulardii CNCM I-745 or LGG from day 1.
- Chronic PPI: talk to your doctor — is it still needed? Annual review is appropriate.
- Chronic NSAID: consider alternatives (acetaminophen, topical, physiotherapy) — with your treating physician.
- New medication start: ask the prescriber or pharmacist about microbiome/GI side effects and the option of gradual introduction.
- Multiple chronic meds: annual pharmacist deprescribing review — especially in the elderly.
- Diarrhea persisting 2 weeks after AB → C. difficile test (stool GDH/toxin)
- Never discontinue PPI on your own — medical supervision
- NSAID side effect (gastric pain, melena, black stool) → urgent
- New drug + unusual GI symptom → prescriber
- Severe diarrhea / mucositis during chemo → oncology center + FMT
Detailed red flags: VII.5 When to See a Doctor chapter.
What's next
Chapter 8 addresses life stages — your microbiome isn't the same in infancy, adulthood, and old age. Knowing age-specific patterns helps with your own and family members' microbiome questions.
References
[28] Vétizou M, Pitt JM, Daillère R et al. Anticancer immunotherapy by CTLA-4 blockade relies on the gut microbiota. Science. 2015. Link
The antitumour effect of CTLA-4 blockade depends on specific Bacteroides species. In mice and patients, T-cell responses against B. thetaiotaomicron or B. fragilis correlated with treatment efficacy. Antibiotic-treated or germ-free mice did not respond to anti-CTLA-4, and the defect was rescued by B. fragilis gavage, polysaccharide immunisation, or transfer of B. fragilis-specific T cells. Faecal microbiota transplantation from humans to mice confirmed that CTLA-4 therapy in melanoma patients favours outgrowth of B. fragilis with anticancer activity.
[122] Costantini L, Molinari R, Farinon B, Merendino N. Impact of Omega-3 Fatty Acids on the Gut Microbiota. Int J Mol Sci. 2017. Link
Long-term dietary habits shape host-specific gut microbiota, but dietary fat effects are less well characterised than those of carbohydrates. The few adult human omega-3 PUFA supplementation studies show consistent changes: decreased Faecalibacterium, increased Bacteroidetes and butyrate-producing Lachnospiraceae. Because dysbiosis of these taxa occurs in inflammatory bowel disease, omega-3 PUFAs may exert a beneficial effect by restoring microbial composition and increasing anti-inflammatory short-chain fatty acid production.
[218] Dethlefsen L, Relman DA. Incomplete recovery and individualized responses of the human distal gut microbiota to repeated antibiotic perturbation. Proc Natl Acad Sci USA. 2011. Link
This longitudinal study examined the distal gut microbiota of three individuals over 10 months spanning two courses of ciprofloxacin, analyzing 1.7 million 16S rRNA sequences from 52-56 samples per subject. Interindividual variation dominated; baseline within-subject communities were stable over months. Ciprofloxacin profoundly reduced diversity and shifted composition within 3-4 days of initiation, with incomplete and individual-specific recovery. The findings characterize gut microbiota resilience and the durable disruption caused by repeated fluoroquinolone exposure.
[222] Forslund K, Hildebrand F, Nielsen T et al. Disentangling type 2 diabetes and metformin treatment signatures in the human gut microbiota. Nature. 2015. Link
Using 784 human gut metagenomes, this study disentangled type 2 diabetes (T2D) microbiome signatures from antidiabetic drug effects and showed antidiabetic medication, particularly metformin, confounds prior T2D dysbiosis associations. The authors provide evidence for microbial mediation of metformin's therapeutic effects through short-chain fatty acid production, and for microbiota-mediated mechanisms behind known GI side effects, including a relative increase in Escherichia species. The findings highlight that treatment status must be controlled when characterizing disease-associated microbiomes.
[229] Maier L, Pruteanu M, Kuhn M et al. Extensive impact of non-antibiotic drugs on human gut bacteria. Nature. 2018. Link
This in vitro screening tested >1000 marketed drugs against 40 representative gut bacterial strains and found that 24% of human-targeted drugs across all therapeutic classes inhibited at least one strain. Antipsychotics were overrepresented in this group. Drug effects on gut bacteria correlated with antibiotic-like side effects in humans and matched existing cohort data. Susceptibility to antibiotics and human-targeted drugs correlated across species, indicating shared resistance mechanisms verified for several drugs. The findings raise concern that non-antibiotics may promote antibiotic resistance.
[560] Thomas RL, Jiang L, Adams JS et al. Vitamin D Metabolites and the Gut Microbiome in Older Men. Nat Commun. 2020. Link
Cross-sectional analysis of 567 older men: higher active 1,25(OH)2D levels were associated with greater abundance of butyrate-producing bacteria (including Faecalibacterium) and higher microbial diversity. Causal direction is undetermined, but the positive association is supported in human data.
[599] Bokulich NA, Chung J, Battaglia T et al. Antibiotics, birth mode, and diet shape microbiome maturation during early life. Sci Transl Med. 2016. Link
Microbial development was profiled in 43 US infants over the first two years of life. Early-life exposures — antibiotic use, cesarean section and formula feeding — were associated with disrupted establishment of maternal bacteria, delayed microbiome development and altered α-diversity. These findings illustrate the complexity of early-life microbiome maturation and its sensitivity to common perturbations during the critical neonatal window — relevant to long-term immune and metabolic risk.
[600] Imhann F, Bonder MJ, Vich Vila A et al. Proton pump inhibitors affect the gut microbiome. Gut. 2016. Link
PPI use and gut microbiota composition were assessed by 16S sequencing in 1815 individuals across three cohorts. PPI users vs non-users were compared per cohort and meta-analyzed. PPIs are among the top 10 most-used drugs worldwide and have been associated with enteric infection risk, particularly Clostridium difficile. The study confirms that PPI use alters gut microbiome composition in directions that may impair colonization resistance — providing mechanistic underpinning for the epidemiological association between PPIs and enteric infection.
[601] Targownik LE, Fisher DA, Saini SD. AGA Clinical Practice Update on De-Prescribing of Proton Pump Inhibitors: Expert Review. Gastroenterology. 2022. Link
A clinical update provides Best Practice Advice statements for PPI de-prescribing in ambulatory patients. PPIs are among the most-prescribed medications and are increasingly used for indications with uncertain benefit, contributing to polypharmacy and economic burden. PPI use has been increasingly associated with PPI-associated adverse events (PAAEs). The guidance promotes structured de-prescribing strategies to reduce pill burden, real costs and theoretical risks while ensuring patients with appropriate indications continue therapy.
[605] Plottel CS, Blaser MJ. Microbiome and malignancy. Cell Host Microbe. 2011. Link
Why only some carcinogen-exposed or genetically predisposed individuals develop cancer is unexplained. Beyond classical factors, the human microbiome — bacteria, archaea, eukaryotes and viruses colonizing humans from birth — has emerged as a modulator. The review presents principles and paradigms of microbiome-related malignancy through three case studies: microbiota effects on local and adjacent neoplasia, the 'estrobolome' model of distant hormonal effects on hormone-dependent cancers, and complex interactions between the microbiome and a latent virus leading to malignancy.
[634] Schmitt FCF, Brenner T, Uhle F et al. Gut microbiome patterns correlate with higher postoperative complication rates after pancreatic surgery. BMC Microbiol. 2019. Link
Prospective clinical pilot study in 32 patients undergoing pancreatic surgery: 116 stool samples were analyzed by 16S rRNA next-generation sequencing. One preoperative baseline sample (without surgical stress/antibiotics) and at least two postoperative samples within 10 days were obtained per patient, with additional samples taken upon postoperative complications. The study aimed to characterize gut-microbiome changes after pancreatic surgery and correlate them with the postoperative course, exploring the microbiome's role in postoperative complications — including barrier dysfunction and bacterial translocation.
[2715] Eng J, Kleinman WA, Singh L, Singh G, Raufman JP. Isolation and characterization of exendin-4, an exendin-3 analogue, from Heloderma suspectum venom. Journal of Biological Chemistry. 1992. Link
Eng and colleagues isolated the peptide exendin-4 from the venom of the Gila monster (Heloderma suspectum). It is structurally similar to the human incretin hormone GLP-1 but resists rapid degradation by DPP-4, giving it a much longer duration of action. This serendipitous discovery became the foundation of the GLP-1 receptor agonist drug class: a synthetic version of exendin-4 (exenatide) became the first approved GLP-1 agonist in 2005, paving the way for today's semaglutide and tirzepatide.
[2716] Wilding JPH, Batterham RL, Calanna S, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1). New England Journal of Medicine. 2021. Link
The STEP 1 phase-3, randomized, placebo-controlled trial (n=1961 adults with overweight/obesity, without diabetes) compared once-weekly subcutaneous semaglutide 2.4 mg with placebo plus lifestyle counselling over 68 weeks. The semaglutide group achieved a mean weight reduction of ~14.9% versus ~2.4% with placebo. The most common adverse events were gastrointestinal (nausea, diarrhea), mostly transient.
[2717] (experimental study, high-fat diet-induced obese mice). Effects of semaglutide on metabolism and gut microbiota in high-fat diet-induced obese mice. Frontiers in Pharmacology. 2025. Link
Animal (high-fat diet-induced obese mouse) study indicating that semaglutide favorably modifies serum metabolism and gut microbiota composition, with part of the metabolic improvement transferable via fecal transplantation. IMPORTANT: this is preclinical, animal-model evidence; human relevance is not yet established, so the claim should be treated as a hypothesis ().