possible causes of SIBO
Medications
Content
1. Medications
1.1 Antibiotics
1.2 Opioids
1.3 Sexual Hormones
1.4 Antispasmodic Drugs
1. Medications
Certain medications may contribute to the development of Small Intestinal Bacterial Overgrowth (SIBO) and even fungal overgrowth such as Candida. Common culprits include antibiotics, opioids/narcotics, hormones (e.g., those used in hormonal contraception), proton pump inhibitors, and antispasmodic drugs. These substances can negatively affect the gut microbiome and overall gut health, leading to a cascade of gastrointestinal disturbances.
1.1 Antibiotics
Antibiotics are widely known to disrupt the gut microbiome. When taken orally, they first interact with gut bacteria in the intestines before reaching their targeted site. This early contact alters microbial diversity and may result in a significant overgrowth of certain bacterial strains. The lack of microbial competition creates ideal conditions for both SIBO and fungal overgrowth, as seen in Candida-dominated gi conditions. Over time, the gut becomes increasingly colonized by resistant or opportunistic microbes, compromising gut health.
1.2 Opioids
One of the most common side effects of opioid-based pain medications is constipation, often due to their ability to slow nerve activity in the gut. This results in dysmotility (1), a known risk factor for both bacterial and fungal overgrowth. Opioids can also alter the gastrointestinal environment by suppressing natural movement and altering microbial composition. Reduced motility allows for prolonged fermentation and microbial stagnation, creating an ideal setting for SIBO or Candida overgrowth (see doi for related research). GI symptoms like bloating, gas, and discomfort may intensify over time.
1.3 Sexual Hormones
Sex hormones such as estrogens and progestins also influence the balance of the gut microbiome (2). These hormones, especially when delivered via oral contraceptives over extended periods, may contribute to both bacterial and fungal imbalances. Clinical observations suggest a link between hormone therapy and symptoms such as bloating, diarrhea, or even skin flare-ups linked to Candida or SIBO. Transdermal or vaginal hormone therapies seem to be less disruptive, as they do not interact directly with intestinal microbes.
1.4 Antispasmodic Drugs
Antispasmodic drugs work by relaxing smooth muscles in the digestive tract. While helpful for managing cramping or discomfort, this effect can reduce gut motility, leading to stagnation and promoting overgrowth—bacterial or fungal. If you are taking antispasmodics regularly and notice worsening gi symptoms, you may benefit from a medication review with your healthcare provider.
References
- Zhang L, Roy S. Opioid Modulation of the Gut-Brain Axis in Opioid-Associated Comorbidities. Cold Spring Harb Perspect Med. 2021 Sep 1;11(9):a040485. doi: 10.1101/cshperspect.a040485. PMID: 32816876; PMCID: PMC8415294.
- Shin, J.H.; Park, Y.H.; Sim, M.; Kim, S.A.; Joung, H.; Shin, D.M. Serum level of sex steroid hormone is associated with diversity and profiles of human gut microbiome. Res. Microbiol. 2019, 170, 192–201
