The "treat empirically" route also has its difficulties, which have all come under wide debate and study. Recommendations are varied but seem to find some common ground around the notion that treatment should be individualized to the specific circumstances under which a patient has developed BLS since these circumstances affect the complex microbial make up of the affected bowel.

Tetracyclines have been the mainstay of treatment for BLS, but recent studies have concluded Rifaximin to be very effective in the treatment of BLS. One study by Di Stefano et al., however, concluded Metronidazole to be more effective than Rifaximin in the treatment of BLS.

The treatment of BLS follows two basic principles. When a patient presents with symptoms of BLS, the treating physician basically has two recognized options for management:

- Test-and-treat

- Treat empirically

Bile acid sequestrants are the main agents used to treat bile acid malabsorption. Cholestyramine and colestipol, both in powder form, have been used for many years. Unfortunately many patients find them difficult to tolerate; although the diarrhea may improve, other symptoms such as pain and bloating may worsen. Colesevelam is a tablet and some patients tolerate this more easily. A proof of concept study of the farnesoid X receptor agonist obeticholic acid has shown clinical and biochemical benefit.

As of March 15, 2016, Novartis Pharmaceuticals is conducting a phase II clinical study involving a farnesoid X receptor agonist named LJN452.

Little is known on the prognosis of achlorhydria, although there have been reports of an increased risk of gastric cancer.

A 2007 review article noted that non-"Helicobacter" bacterial species can be cultured from achlorhydric (pH > 4.0) stomachs, whereas normal stomach pH only permits the growth of "Helicobacter" species. Bacterial overgrowth may cause false positive H. Pylori test results due to the change in pH from urease activity.

Small bowel bacterial overgrowth is a chronic condition. Retreatment may be necessary once every 1–6 months. Prudent use of antibacterials now calls for an antibacterial stewardship policy to manage antibiotic resistance.

Prucalopride, pyridostigmine, metoclopramide, cisapride, and erythromycin may be used, but they have not been shown to have great efficacy. In such cases, treatment is aimed at managing the complications. Linaclotide is a new drug that received approval from Food and Drug Administration in August 2012 and looks promising in the treatment of chronic intestinal pseudo-obstruction, gastroparesis and inertia coli.

Intestinal stasis, which may lead to bacterial overgrowth and subsequently, diarrhea or malabsorption, is treated with antibiotics.

Nutritional deficiencies are treated by encouraging patients to avoid food high in fat and fibre, which are harder to digest and increase abdominal distention and discomfort, and have small, frequent meals (5–6 per day), focusing on liquids and soft food. Reducing intake of poorly absorbed sugar alcohols may be of benefit. Referral to an accredited dietitian is recommended. If dietary changes are unsuccessful in meeting nutritional requirements and stemming weight loss, enteral nutrition is used. Many patients eventually require parenteral nutrition.

Total parenteral nutrition (TPN) is a form of long-term nutritional treatment needed for patients that have severe pseudoobstruction. After a period of no improvement of intestinal function or motility the decision to start TPN will be made, and the surgical procedure to add a long-term, more permanent IV to administer TPN will occur. Types of IV catheters to be placed will be a PICC line or central line which include mediports, Broviac, or Hickman lines depending on how long the physicians believe the patient will require TPN. Patients that are deemed TPN dependent will require constant checkups to monitor the catheter is working properly, check liver enzyme levels and look for signs of blood infections, as catheter blockage, liver damage, and infections of catheters are the main complications associated with long term TPN use and can result in sepsis and/or additional surgeries if not properly monitored. TPN nutritional feeds are given over a period of several hours to all day infusions, and are a mixture of all the vitamins, minerals, and calories similar to what one would get eating orally daily as well as any other specific nutritional needs the patient has at the moment. TPN format is typically changed depending on loss/gain of weight and bloodwork results, and is specially formulated to meet each individual patient's needs.

Use of octreotide has been described.

Cannabis has long been known to limit or prevent nausea and vomiting from a variety of causes. This has led to extensive investigations that have revealed an important role for cannabinoids and their receptors in the regulation of nausea and emesis. With the discovery of the endocannabinoid system, novel ways to regulate both nausea and vomiting have been discovered that involve the production of endogenous cannabinoids acting centrally. The plant cannabis has been used in clinics for centuries, and has been known to be beneficial in a variety of gastrointestinal diseases, such as emesis, diarrhea, inflammatory bowel disease and intestinal pain. Moreover, modulation of the endogenous cannabinoid system in the gastrointestinal tract may provide a useful therapeutic target for gastrointestinal disorders. While some GI disorders may be controlled by diet and pharmaceutical medications, others are poorly moderated by conventional treatments. Symptoms of GI disorders often include cramping, abdominal pain, inflammation of the lining of the large and/or small intestine, chronic diarrhea, rectal bleeding and weight loss. Patients with these disorders frequently report using cannabis therapeutically.

In a 2012 animal study, cannabichromene was shown to normalize gastrointestinal hypermotility without reducing the transit time. The study notes that this result is of potential clinical interest, as the only drugs available for intestinal dysmotility are often associated with constipation.

Secondary chronic intestinal pseudo-obstruction is managed by treating the underlying condition.

There is no cure for primary chronic intestinal pseudo-obstruction. It is important that nutrition and hydration is maintained, and pain relief is given. Drugs that increase the propulsive force of the intestines have been tried, as have different types of surgery.

Treatment focuses on addressing the underlying cause of symptoms.

Treatment of gastritis that leads to pernicious anemia consists of parenteral vitamin B-12 injection. Associated immune-mediated conditions (e.g., insulin dependent diabetes mellitus, autoimmune thyroiditis) should also be treated. However, treatment of these disorders has no known effect in the treatment of achlorhydria.

Achlorhydria associated with "Helicobacter pylori" infection may respond to H pylori eradication therapy, although resumption of gastric acid secretion may only be partial and it may not always reverse the condition completely.

Antimicrobial agents, including metronidazole, amoxicillin/clavulanate potassium, ciprofloxacin, and rifaximin, can be used to treat bacterial overgrowth.

Achlorhydria resulting from long-term proton-pump inhibitor (PPI) use may be treated by dose reduction or withdrawal of the PPI.

Prevention focuses on improving sanitation of water and food sources.

Treatment focuses on addressing the central components of intestinal inflammation, bacterial overgrowth and nutritional supplementation.

Some studies reported up to 80% of patients with irritable bowel syndrome (IBS) have SIBO (using the hydrogen breath test). Subsequent studies demonstrated statistically significant reduction in IBS symptoms following therapy for SIBO.

There is a lack of consensus however, regarding the suggested link between IBS and SIBO. Other authors concluded that the abnormal breath results so common in IBS patients do not suggest SIBO, and state that "abnormal fermentation timing and dynamics of the breath test findings support a role for abnormal intestinal bacterial distribution in IBS." There is general consensus that breath tests are abnormal in IBS; however, the disagreement lies in whether this is representative of SIBO. More research is needed to clarifiy this possible link.

Bacterial overgrowth is usually treated with a course of antibiotics although whether antibiotics should be a first line treatment is a matter of debate. Some experts recommend probiotics as first line therapy with antibiotics being reserved as a second line treatment for more severe cases of SIBO. Prokinetic drugs are other options but research in humans is limited. A variety of antibiotics, including tetracycline, amoxicillin-clavulanate, fluoroquinolones, metronidazole, neomycin, cephalexin, trimethoprim-sulfamethoxazole, and nitazoxanide have been used; however, the best evidence is for the use of rifaximin.

A course of one week of antibiotics is usually sufficient to treat the condition. However, if the condition recurs, antibiotics can be given in a cyclical fashion in order to prevent tolerance. For example, antibiotics may be given for a week, followed by three weeks off antibiotics, followed by another week of treatment. Alternatively, the choice of antibiotic used can be cycled.

The condition that predisposed the patient to bacterial overgrowth should also be treated. For example, if the bacterial overgrowth is caused by chronic pancreatitis, the patient should be treated with coated pancreatic enzyme supplements.

Probiotics are bacterial preparations that alter the bacterial flora in the bowel to cause a beneficial effect. Animal research has demonstrated that probiotics have barrier enhancing, antibacterial, immune modulating and anti-inflammatory effects which may have a positive effect in the management of SIBO in humans. "Lactobacillus casei" has been found to be effective in improving breath hydrogen scores after 6 weeks of treatment presumably by suppressing levels of a small intestinal bacterial overgrowth of fermenting bacteria. The multi-strain preparation VSL#3 was found to be effective in suppressing SIBO. "Lactobacillus plantarum", "Lactobacillus acidophilus", and "Lactobacillus casei" have all demonstrated effectiveness in the treatment and management of SIBO. Conversely, "Lactobacillus fermentum" and "Saccharomyces boulardii" have been found to be ineffective. A combination of "Lactobacillus plantarum" and "Lactobacillus rhamnosus" has been found to be effective in suppressing bacterial overgrowth of abnormal gas producing organisms in the small intestine.

Probiotics are superior to antibiotics in the treatment of SIBO. A combination of probiotic strains has been found to produce better results than therapy with the antibiotic drug metronidazole and probiotics have been found to be effective in treating and preventing secondary lactase deficiency and small intestinal bacteria overgrowth in individuals suffering from post-infectious irritable bowel syndrome. Probiotics taken in uncomplicated cases of SIBO can usually result in the individual becoming symptom free. Probiotic therapy may need to be taken continuously to prevent the return of overgrowth of gas producing bacteria. A study by the probiotic yogurt producer Nestlé found that probiotic yogurt may also be effective in treating SIBO with evidence of reduced inflammation after 4 weeks of treatment.

An elemental diet taken for two weeks is an alternative to antibiotics for eliminating SIBO. An elemental diet works via providing nutrition for the individual while depriving the bacteria of a food source. Additional treatment options include the use of prokinetic drugs such as 5-HT4 receptor agonists or motilin agonists to extend the SIBO free period after treatment with an elemental diet or antibiotics. A diet void of certain foods that feed the bacteria can help alleviate the symptoms. For example, if the symptoms are caused by bacterial overgrowth feeding on indigestible carbohydrate rich foods, following a FODMAP restriction diet may help.

There are multiple large-field, multi-country research initiatives focusing on strategies to prevent and treat EE.

- The MAL-ED project

- The Alive and Thrive nutrition project

- The Sanitation, Hygiene and Infant Nutrition Efficacy (SHINE) Trial (ClinicalTrials.gov identifier: NCT01824940)

- The WASH Benefits Study

The most reliable test for EPI in dogs and cats is serum trypsin-like immunoreactivity (TLI). A low value indicates EPI. Fecal elastase levels may also be used for diagnosis in dogs.

In dogs, the best treatment is to supplement its food with dried pancreatic extracts. There are commercial preparations available, but chopped bovine pancreas from the butcher can also be used (pork pancreas should not be used because of the rare transmission of pseudorabies). Symptoms usually improve within a few days, but lifelong treatment is required to manage the condition. A rare side-effect of use of dried pancreatic extracts is oral ulceration and bleeding.

Because of malabsorption, serum levels of cyanocobalamin (vitamin B12) and tocopherol (vitamin E) may be low. These may be supplemented, although since cyanocobalamin contains the toxic chemical cyanide, dogs that have serious cobalamin issues should instead be treated with hydroxocobalamin or methylcobalamin. Cyanocobalamin deficiency is very common in cats with EPI because about 99 percent of intrinsic factor (which is required for cyanocobalamin absorption from the intestine) is secreted by the pancreas. In dogs, this figure is about 90 percent, and only about 50 percent of dogs have this deficiency. Cats may suffer from Vitamin K deficiencies. If there is bacterial overgrowth in the intestine, antibiotics should be used, especially if treatment is not working. In dogs failing to gain weight or continuing to show symptoms, modifying the diet to make it low-fiber and highly digestible may help. Despite previous belief that low-fat diets are beneficial in dogs with EPI, more recent studies have shown that a high-fat diet may increase absorption of nutrients and better manage the disease. However, it has been shown that different dogs respond to different dietary modifications, so the best diet must be determined on a case-by-case basis.

One possible sequela, volvulus (mesenteric torsion) is a rare consequence of EPI in dogs.

Some evidence suggests soluble fiber supplementation (e.g., psyllium/ispagula husk) is effective. It acts as a bulking agent, and for many IBS-D patients, allows for a more consistent stool. For IBS-C patients, it seems to allow for a softer, moister, more easily passable stool.

However, insoluble fiber (e.g., bran) has not been found to be effective for IBS. In some people, insoluble fiber supplementation may aggravate symptoms.

Fiber might be beneficial in those who have a predominance of constipation. In people who have IBS-C, soluble fiber can reduce overall symptoms, but will not reduce pain. The research supporting dietary fiber contains conflicting small studies complicated by the heterogeneity of types of fiber and doses used.

One meta-analysis found only soluble fiber improved global symptoms of irritable bowel, but neither type of fiber reduced pain.

An updated meta-analysis by the same authors also found soluble fiber reduced symptoms, while insoluble fiber worsened symptoms in some cases. Positive studies have used 10–30 grams per day of ispaghula (psyllium). One study specifically examined the effect of dose, and found 20 g of ispaghula (psyllium) were better than 10 g and equivalent to 30 g per day.

Individuals with IBS have been found to have decreased diversity and numbers of bacteroidetes microbiota. Preliminary research into the effectiveness of fecal microbiota transplant in the treatment of IBS has been very favourable with a 'cure' rate of between 36 percent and 60 percent with remission of core IBS symptoms persisting at 9 and 19 months follow up. Treatment with probiotic strains of bacteria has shown to be effective, though not all strains of microorganisms confer the same benefit and adverse side effects have been documented in a minority of cases.

There is increasing evidence for the effectiveness of mesalazine (5-aminosalicylic acid) in the treatment of IBS. Mesalazine is a drug with anti-inflammatory properties that has been reported to significantly reduce immune mediated inflammation in the gut of IBS affected individuals with mesalazine therapy resulting in improved IBS symptoms as well as feelings of general wellness in IBS affected people. It has also been observed that mesalazine therapy helps to normalise the gut flora which is often abnormal in people who have IBS. The therapeutic benefits of mesalazine may be the result of improvements to the epithelial barrier function.

An IgG-mediated food intolerance diet led to a 24% greater deterioration in symptoms compared to those on the elimination diet and food elimination based on IgG antibodies may be effective in reducing IBS symptoms and is worthy of further biomedical research. The main problem with this study was that the differences in symptoms were only observed in exclusion diets is limited, treatment based on "abnormally" high IgG antibodies cannot be recommended.

Differences in visceral sensitivity and intestinal physiology have been noted in IBS. Mucosal barrier reinforcement in response to oral 5-HTP was absent in IBS compared to controls. IBS/IBD individuals are less often HLA DQ2/8 positive than in upper functional gastrointestinal disease and healthy populations.

A questionnaire in 2006 designed to identify patients' perceptions about IBS, their preferences on the type of information they need, and educational media and expectations from health care providers revealed misperceptions about IBS developing into other conditions, including colitis, malnutrition, and cancer. The survey found IBS patients were most interested in learning about foods to avoid (60%), causes of IBS (55%), medications (58%), coping strategies (56%), and psychological factors related to IBS (55%). The respondents indicated they wanted their physicians to be available by phone or e-mail following a visit (80%), have the ability to listen (80%), and provide hope (73%) and support (63%).

Bile acid malabsorption, known also as bile acid diarrhea, is a cause of several gut-related problems, the main one being chronic diarrhea. It has also been called bile acid-induced diarrhea, cholerheic or choleretic enteropathy and bile salt malabsorption. It can result from malabsorption secondary to gastrointestinal disease, or be a primary disorder, associated with excessive bile acid production. Treatment with bile acid sequestrants is often effective.

Antibiotic-associated diarrhea (AAD) results from an imbalance in the colonic microbiota caused by antibiotic therapy. Microbiota alteration changes carbohydrate metabolism with decreased short-chain fatty acid absorption and an osmotic diarrhea as a result. Another consequence of antibiotic therapy leading to diarrhea is overgrowth of potentially pathogenic organisms such as "Clostridium difficile". It is defined as frequent loose and watery stools with no other complications.

Meta-analyses have concluded that probiotics may protect against antibiotic-associated diarrhea in both children and adults. Evidence is insufficient, however, regarding an effect on rates of "Clostridium difficile" colitis.

However, citing conflicting data in the studies, other sources claim that the use of probiotics has failed thus far to meet the standard of medical care required for evidence-based medicine. Demonstration of the efficacy of probiotics is needed by randomized, double blind, placebo-controlled trials.

Efficacy of probiotic AAD prevention is dependent on the probiotic strain(s) used and on the dosage. Up to a 50% reduction of AAD occurrence has been found. No side-effects have been reported in any of these studies. Caution should, however, be exercised when administering probiotic supplements to immunocompromised individuals or patients who have a compromised intestinal barrier because of the risk of an infection caused by the probiotic supplements.

"Clostridium difficile", also known more commonly as "C. diff", is known to account for 10 to 20 percent of antibiotic-associated diarrhea cases. The reasoning for this, is that the antibiotics administered for the treatment of certain diseases processes such as inflammatory colitis also inadvertently kills a large portion of the gut flora, the normal flora that is usually present within the bowel. With this lower amount of "healthy" bacteria present, the overgrowth of "C. diff" is then responsible "for elaborating the enterotoxin".

Prevention of radiation injury to the small bowel is a key aim of techniques such as brachytherapy, field size, multiple field arrangements, conformal radiotherapy techniques and intensity-modulated radiotherapy. Medications including ACE inhibitors, statins and probiotics have also been studied and reviewed.

In people presenting with symptoms compatible with radiation enteropathy, the initial step is to identify what is responsible for causing the symptoms. Management is best with a multidisciplinary team including gastroenterologists, nurses, dietitians, surgeons and others.

Medical treatments include the use of hyperbaric oxygen which has beneficial effects in radiation proctitis or anal damage. Nutritional therapies include treatments directed at specific malabsorptive disorders such as low fat diets and vitamin B12 or vitamin D supplements, together with bile acid sequestrants for bile acid diarrhea and possibly antibiotics for small intestinal bacterial overgrowth. Probiotics have all been suggested as another therapeutic avenue.

Endoscopic therapies including argon plasma coagulation have been used for bleeding telangiectasia in radiation proctitis and at other intestinal sites, although there is a rick of perforation. Sucralfate enemas look promising in proctitis.

Surgical treatment may be needed for intestinal obstruction, fistulae, or perforation, which can happen in more severe cases. These can be fatal if patients present as an emergency, but with improved radiotherapy techniques are now less common.

Optimal treatment usually produces significant improvements in quality of life.

Chronic pancreatitis is the most common cause of EPI in cats. In dogs, where the condition has been deemed common, the usual cause is by "pancreatic acinar atrophy", arising as a result of genetic conditions, a blocked pancreatic duct, or prior infection.

In dogs, EPI is most common in young German Shepherd Dogs, and Rough Collies in Finland, in which it is inherited. In the German Shepherd Dog, the method of inheritance is through an autosomal recessive gene. In these two breeds, at least, the cause appears to be immune-mediated as a sequela to lymphocytic pancreatitis. The German Shepherd Dog makes up about two-thirds of cases seen with EPI. Other breeds reported to be predisposed to EPI include terrier breeds, Cavalier King Charles Spaniels, Chow Chows and Picardy Shepherd.

Treatment includes dietary changes (low fiber diets) and, in some cases, restrictions on fat and/or solids. Eating smaller meals, spaced two to three hours apart has proved helpful. Avoiding foods that cause the individual problems, such as pain in the abdomen, or constipation, such as rice or beef, will help avoid symptoms.

Metoclopramide, a dopamine D receptor antagonist, increases contractility and resting tone within the GI tract to improve gastric emptying. In addition, dopamine antagonist action in the central nervous system prevents nausea and vomiting. Similarly, the dopamine receptor antagonist domperidone is also used to treat gastroparesis. Erythromycin is known to improve emptying of the stomach but its effects are temporary due to tachyphylaxis and wane after a few weeks of consistent use.

Sildenafil citrate, which increases blood flow to the genital area in men, is being used by some practitioners to stimulate the gastrointestinal tract in cases of diabetic gastroparesis.

The antidepressant mirtazapine has proven effective in the treatment of gastroparesis unresponsive to conventional treatment. This is due to its antiemetic and appetite stimulant properties. Mirtazapine acts on the same serotonin receptor (5-HT3) as does the popular anti-emetic ondansetron.

In specific cases where treatment of chronic nausea and vomiting proves resistant to drugs, implantable gastric stimulation may be utilized. A medical device is implanted that applies neurostimulation to the muscles of the lower stomach to reduce the symptoms. This is only done in refractory cases that have failed all medical management (usually at least 2 years of treatment). Medically refractory gastroparesis may also be treated with a pyloromyotomy, which widens the gastric outlet by cutting the circular pylorus muscle. This can be done laparoscopically or endoscopically.

Transient gastroparesis may arise in acute illness of any kind, as a consequence of certain cancer treatments or other drugs which affect digestive action, or due to abnormal eating patterns.

It is frequently caused by autonomic neuropathy. This may occur in people with type 1 or type 2 diabetes. In fact, diabetes mellitus has been named as the most common cause of gastroparesis, as high levels of blood glucose may effect chemical changes in the nerves. The vagus nerve becomes damaged by years of high blood glucose or insufficient transport of glucose into cells resulting in gastroparesis. Gastroparesis has also been associated with connective tissue diseases such as scleroderma and Ehlers–Danlos syndrome, and neurological conditions such as Parkinson's disease. It may also occur as part of a mitochondrial disease. Opioids and anticholinergic medications can cause medication-induced gastroparesis.

Chronic gastroparesis can be caused by other types of damage to the vagus nerve, such as abdominal surgery. Heavy cigarette smoking is also a plausible cause since smoking causes damage to the stomach lining.

Idiopathic gastroparesis (gastroparesis with no known cause) accounts for a third of all chronic cases; it is thought that many of these cases are due to an autoimmune response triggered by an acute viral infection. Gastroenteritis, mononucleosis, and other ailments have been anecdotally linked to the onset of the condition, but no systematic study has proven a link.

Gastroparesis sufferers are disproportionately female. One possible explanation for this finding is that women have an inherently slower stomach emptying time than men. A hormonal link has been suggested, as gastroparesis symptoms tend to worsen the week before menstruation when progesterone levels are highest. Neither theory has been proven definitively.

Gastroparesis can also be connected to hypochlorhydria and be caused by chloride, sodium and/or zinc deficiency, as these minerals are needed for the stomach to produce adequate levels of gastric acid (HCl) in order to properly empty itself of a meal.

Preventive measures for visitors to tropical areas where the condition exists include steps to reduce the likelihood of gastroenteritis. These may comprise using only bottled water for drinking, brushing teeth, and washing food, and avoiding fruits washed with tap water (or consuming only peeled fruits, such as bananas and oranges). Basic sanitation is necessary to reduce fecal-oral contamination and the impact of environmental enteropathy in the developing world.

Once diagnosed, tropical sprue can be treated by a course of the antibiotic tetracycline or sulphamethoxazole/trimethoprim (co-trimoxazole) for 3 to 6 months.

Supplementation of vitamins B and folic acid improves appetite and leads to a gain in weight.

The oral cholera vaccine, while effective for prevention of cholera, is of questionable use for prevention of TD. A 2008 review found tentative evidence of benefit. A 2015 review stated it may be reasonable for those at high risk of complications from TD. Several vaccine candidates targeting ETEC or "Shigella" are in various stages of development.

Other preventive options include over-the-counter antidiarrhea products and antibiotics.

Bismuth subsalicylate four times daily reduces rates of traveler's diarrhea. Though many travelers find a four-times-per-day regimen inconvenient, lower doses have not been shown to be effective. Potential side effects include black tongue, black stools, nausea, constipation, and ringing in the ears. Bismuth subsalicylate should not be taken by those with aspirin allergy, kidney disease, or gout, nor concurrently with certain antibiotics such as the quinolones, and should not be taken continuously for more than three weeks. Some countries do not recommend it due to the risk of rare but serious side effects.

A hyperimmune bovine colostrum to be taken by mouth is marketed in Australia for prevention of ETEC-induced TD. As yet, no studies show efficacy under actual travel conditions.

Though effective, antibiotics are not recommended for prevention of TD in most situations because of the risk of allergy or adverse reactions to the antibiotics, and because intake of preventive antibiotics may decrease effectiveness of such drugs should a serious infection develop subsequently. Antibiotics can also cause vaginal yeast infections, or overgrowth of the bacterium "Clostridium difficile", leading to pseudomembranous colitis and its associated severe, unrelenting diarrhea.

Antibiotic prophylaxis may be warranted in special situations where benefits outweigh the above risks, such as immunocompromised travelers, chronic intestinal disorders, prior history of repeated disabling bouts of TD, or scenarios in which the onset of diarrhea might prove particularly troublesome. Options for prophylactic treatment include the quinolone antibiotics (such as ciprofloxacin), azithromycin, and trimethoprim/sulfamethoxazole, though the latter has proved less effective in recent years. Rifaximin may also be useful. Quinolone antibiotics may bind to metallic cations such as bismuth, and should not be taken concurrently with bismuth subsalicylate. Trimethoprim/sulfamethoxazole should not be taken by anyone with a history of sulfa allergy.