Sulfasalazine has been a major agent in the therapy of mild to moderate ulcerative colitis for over 50 years. In 1977, Mastan S. Kalsi "et al." determined that 5-aminosalicylic acid (5-ASA and mesalazine) was the therapeutically active component in sulfasalazine. Since then, many 5-ASA compounds have been developed with the aim of maintaining efficacy but reducing the common side effects associated with the sulfapyridine moiety in sulfasalazine.

Ulcerative colitis can be treated with a number of medications, including 5-ASA drugs such as sulfasalazine and mesalazine. Corticosteroids such as prednisone can also be used due to their immunosuppressive and short-term healing properties, but because their risks outweigh their benefits, they are not used long-term in treatment. Immunosuppressive medications such as azathioprine and biological agents such as infliximab and adalimumab are given only if people cannot achieve remission with 5-ASA and corticosteroids. Such treatments are used less commonly due to their possible risk factors, including but not limited to increased risk of cancers in teenagers and adults, tuberculosis, and new or worsening heart failure (these side effects are rare). A formulation of budesonide was approved by the FDA for treatment of active ulcerative colitis in January 2013. The evidence on methotrexate does not show a benefit in producing remission in people with ulcerative colitis. Off-label use of drugs such as ciclosporin and tacrolimus has shown some benefits. Fexofenadine, an antihistamine drug used in treatment of allergies, has shown promise in a combination therapy in some studies. Opportunely, low gastrointestinal absorption (or high absorbed drug gastrointestinal secretion) of fexofenadine results in higher concentration at the site of inflammation. Thus, the drug may locally decrease histamine secretion by involved gastrointestinal mast cells and alleviate the inflammation.

Medical treatment of IBD is individualised to each patient. The choice of which drugs to use and by which route to administer them (oral, rectal, injection, infusion) depends on factors including the type, distribution, and severity of the patient's disease, as well as other historical and biochemical prognostic factors, and patient preferences. For example, mesalazine is more useful in ulcerative colitis than in Crohn's disease. Generally, depending on the level of severity, IBD may require immunosuppression to control the symptoms, with drugs such as prednisone, TNF inhibitors, azathioprine (Imuran), methotrexate, or 6-mercaptopurine.

Steroids, such as the glucocorticoid prednisone, are frequently used to control disease flares and were once acceptable as a maintenance drug. Biological therapy for inflammatory bowel disease, especially the TNF inhibitors, are used in people with more severe or resistant Crohn's disease and sometimes in ulcerative colitis.

Treatment is usually started by administering drugs with high anti-inflammatory effects, such as prednisone. Once the inflammation is successfully controlled, another drug to keep the disease in remission, such as mesalazine in UC, is the main treatment. If further treatment is required, a combination of an immunosuppressive drug (such as azathioprine) with mesalazine (which may also have an anti-inflammatory effect) may be needed, depending on the patient. Controlled release Budesonide is used for mild ileal Crohn's disease.

Nutritional deficiencies play a prominent role in IBD. Malabsorption, diarrhea, and GI blood loss are common features of IBD. Deficiencies of B vitamins, fat-soluble vitamins, essential fatty acids, and key minerals such as magnesium, zinc, and selenium are extremely common and benefit from replacement therapy. Dietary interventions, including certain exclusion diets, low fiber diets, and low FODMAP diets have some benefits.

Anaemia is commonly present in both ulcerative colitis and Crohn's disease. Due to raised levels of inflammatory cytokines which lead to the increased expression of hepcidin, parenteral iron is the preferred treatment option as it bypasses the gastrointestinal system, has lower incidence of adverse events and enables quicker treatment. Hepcidin itself is also an anti-inflammatory agent. In the murine model very low levels of iron restrict hepcidin synthesis, worsening the inflammation that is present. Enteral nutrition has been found to be efficient to improve hemoglobin level in patients with inflammatory bowel disease, especially combined with erythropoietin.

Lymphocytic and collagenous colitis have both been shown in randomized, placebo-controlled trials to respond well to budesonide, a glucocorticoid. Budesonide formulated to be active in the distal colon and rectum is effective for both active disease and in the prevention of relapse. However, relapse occurs frequently after withdrawal of therapy.

Studies of a number of other agents including antidiarrheals, bismuth subsalicylate (Pepto-Bismol), mesalazine/mesalamine (alone or in combination with cholestyramine), systemic corticosteroids, cholestyramine, immunomodulators, and probiotics have shown to be less effective than budesonide for treating both forms of microscopic colitis.

Anti-TNF inhibitors. split ileostomy, diverting ileostomy, and subtotal colectomy are options for management of steroid-dependent or refractory microscopic colitis. Currently, the need to resort to surgery is limited considering the improvement of drug therapy options. However, surgery is still considered for patients with severe, unresponsive microscopic colitis.

Acute treatment uses medications to treat any infection (normally antibiotics) and to reduce inflammation (normally aminosalicylate anti-inflammatory drugs and corticosteroids). When symptoms are in remission, treatment enters maintenance, with a goal of avoiding the recurrence of symptoms. Prolonged use of corticosteroids has significant side-effects; as a result, they are, in general, not used for long-term treatment. Alternatives include aminosalicylates alone, though only a minority are able to maintain the treatment, and many require immunosuppressive drugs. It has been also suggested that antibiotics change the enteric flora, and their continuous use may pose the risk of overgrowth with pathogens such as "Clostridium difficile".

Medications used to treat the symptoms of Crohn's disease include 5-aminosalicylic acid (5-ASA) formulations, prednisone, immunomodulators such as azathioprine (given as the prodrug for 6-mercaptopurine), methotrexate, infliximab, adalimumab, certolizumab and natalizumab. Hydrocortisone should be used in severe attacks of Crohn's disease. Biological therapies (biopharmaceuticals) are medications used to avoid long-term steroid use, decrease inflammation, and treat people who have fistulas with abscesses. The monoclonal antibody ustekinumab appears to be a safe treatment option, and may help people with moderate to severe active Crohn's disease. The long term safety and effectiveness of monoclonal antibody treatment is not known. The monoclonal antibody briakinumab is not effective for people with active Crohn's disease.

The gradual loss of blood from the gastrointestinal tract, as well as chronic inflammation, often leads to anemia, and professional guidelines suggest routinely monitoring for this. Adequate disease control usually improves anemia of chronic disease, but iron deficiency may require treatment with iron supplements. Guidelines vary as to how iron should be administered. Besides other, problems include a limitation in possible daily resorption and an increased growth of intestinal bacteria. Some advise parenteral iron as first line as it works faster, has fewer gastrointestinal side effects, and is unaffected by inflammation reducing enteral absorption.

Other guidelines advise oral iron as first line with parenteral iron reserved for those that fail to adequately respond as oral iron is considerably cheaper. All agree that severe anemia (hemoglobin under 10g/dL) should be treated with parenteral iron. Blood transfusion should be reserved for those who are cardiovascularly unstable, due to its relatively poor safety profile, lack of long term efficacy, and cost.

Some people may be admitted into the hospital following the colonoscopy depending on results. It is sometimes necessary to get the patient started on a steroid to speed up the healing of the colon. It may also be necessary to get the patient hydrated from the fluid loss and iron replaced from the loss of blood. After a hospital stay, the patient may be put on a daily medication to manage their chronic colitis. The medication can be an anti-inflammatory or an immunosuppressant. There are many different types of medication used and the doctor will prescribe the one they see fit. If the patient doesn't respond, new medications will be tried until there is a good fit.

Moreover, several studies recently have found significant relationship between colitis and dairy allergy (including: cow milk, cow milk UHT and casein), suggesting some patients may benefit from an elimination diet.

Certain lifestyle changes can reduce symptoms, including dietary adjustments, elemental diet, proper hydration, and smoking cessation. Diets that include higher levels of fiber and fruit are associated with reduced risk, while diets rich in total fats, polyunsaturated fatty acids, meat, and omega-6 fatty acids may increase the risk of Crohn's. Smoking may increase Crohn's disease; stopping is recommended. Eating small meals frequently instead of big meals may also help with a low appetite. To manage symptoms have a balanced diet with proper portion control. Fatigue can be helped with regular exercise, a healthy diet, and enough sleep. A food diary may help with identifying foods that trigger symptoms. Some people should follow a low fiber diet to control acute symptoms especially if fibrous foods cause symptoms. Some find relief in eliminating casein (protein found in cow's milk) and gluten (protein found in wheat, rye and barley) from their diets. They may have specific dietary intolerances (not allergies).

Budesonide, in colonic release preparations, has been shown in randomized controlled trials to be effective in treating this disorder. It helps control the diarrheal symptoms and treatment is usually given for several weeks. Sometimes it is used to prevent frequent relapses.

Over-the-counter antidiarrheal drugs may be effective for some people with lymphocytic colitis. Anti-inflammatory drugs, such as salicylates, mesalazine, and systemic corticosteroids may be prescribed for people who do not respond to other drug treatment. The long-term prognosis for this disease is good with a proportion of people suffering relapses which respond to treatment.

There is no clinically approved treatment for pouchitis.

First line treatment is usually with antibiotics, specifically with ciprofloxacin and metronidazole. Ampicillin or Piperacillin can also be considered as alternatives to empiric Ciprofloxacin and metronidazole). Administration of metronidazole at a high daily dose of 20 mg/kg can cause symptomatic peripheral neuropathology in up to 85% of patients. This can be a limiting factor in the use of maintenance metronidazole to suppress chronic pouchitis.

Other therapies which have been shown to be effective in randomised clinical trials include probiotic therapy, the application of which usually begins as soon as any antibiotic course is completed so as to re-populate the pouch with beneficial bacteria. Biologics, such as anti-TNF antibodies, may also be useful but the evidence for their use is largely anecdotal. In addition, discussion by patients using related internet forums appears to give evidence of benefits (again, after cessation of antibiotics) from certain diets, such as the Specific Carbohydrate Diet, Paleolithic Diet, and Low FODMAP Diet. In particular, attention has been drawn to the exclusion of complex carbohydrates, as well as other foods with high starch content (such as grains, rice, and potatoes) and certain dairy products including milk and soft cheese.

Antisense inhibitors which target the inflammatory process have been used to treat pouchitis in clinical trials. Antisense inhibitors function by binding to messenger RNA (mRNA) produced by a gene and deactivating it, effectively turning that gene "off". Specifically applied to pouchitis, antisense inhibitors would be used to switch off the inflammatory process.

Treatment of collagenous colitis is often challenging. Typically, one or more of the following therapeutic agents are used:

- Bismuth agents, including Pepto-Bismol

- 5-aminosalicylic acid

- Budesonide

- Immunosuppressants, including azathioprine

- Corticosteroids

Pilot-scale studies have shown some evidence of possible benefit for both "Boswellia serrata" extract and specific strains of probiotics in the treatment of collagenous colitis, although larger sample sizes are needed to confirm the results.

The prognosis for lymphocytic colitis and collagenous colitis is good, and both conditions are considered to be benign. The majority of people afflicted with the conditions recover from their diarrhea, and their histological abnormalities resolve, although relapses commonly occur if maintenance treatment is not continued.

Mild cases usually do not require treatment and will go away after a few days in healthy people. In cases where symptoms persist or when it is more severe, specific treatments based on the initial cause may be required.

In cases where diarrhoea is present, replenishing fluids lost is recommended, and in cases with prolonged or severe diarrhoea which persists, intravenous rehydration therapy or antibiotics may be required. A simple oral rehydration therapy (ORS) can be made by dissolving one teaspoon of salt, eight teaspoons of sugar and the juice of an orange into one litre of clean water. Studies have shown the efficacy of antibiotics in reducing the duration of the symptoms of infectious enteritis of bacterial origin, however antibiotic treatments are usually not required due to the self-limiting duration of infectious enteritis.

The usual treatment is antivirals, specifically ganciclovir or valganciclovir. Severe CMV colitis may lead a colectomy.

The objective of treatment is to decompress the bowel and to prevent swallowed air from further distending the bowel. If decompression is not achieved or the patient does not improve within 24 hours, a colectomy (surgical removal of all or part of the colon) is indicated. When surgery is required the recommended procedure is a subtotal colectomy with end ileostomy. Fluid and electrolyte replacement help to prevent dehydration and shock. Use of corticosteroids may be indicated to suppress the inflammatory reaction in the colon if megacolon has resulted from active inflammatory bowel disease. Antibiotics may be given to prevent sepsis.

Cuffitis is treated with mesalamine suppositories or topical application of lidocaine or corticosteroid medications. Systemic medications are rarely used.

No pharmacologic treatment has been approved by the U.S. Food and Drug Administration for PSC. Some experts recommend a trial of ursodeoxycholic acid (UDCA), a bile acid occurring naturally in small quantities in humans, as it has been shown to lower elevated liver enzyme numbers in patients with PSC and has proven effective in other cholestatic liver diseases. However, UDCA has yet to be shown to clearly lead to improved liver histology and survival. Guidelines from the American Association for the Study of Liver Diseases and the American College of Gastroenterology do not support the use of UDCA but guidelines from the European Association for the Study of the Liver do endorse the use of moderate doses (13-15 milligrams per kilogram) of UDCA for PSC.

Supportive treatment for PSC symptoms is the cornerstone of management. These therapies are aimed at relieving symptoms such as itching with antipruritics (e.g. bile acid sequestrants such as (cholestyramine)); antibiotics to treat episodes of acute cholangitis; and vitamin supplements, as people with PSC are often deficient in fat-soluble vitamins (vitamin A, vitamin D, vitamin E, and vitamin K).

ERCP and specialized techniques may also be needed to help distinguish between a benign PSC stricture and a bile duct cancer (cholangiocarcinoma).

Liver transplantation is the only proven long-term treatment of PSC, although only a fraction of individuals with PSC will need it. Indications for transplantation include recurrent bacterial cholangitis, decompensated cirrhosis, hepatocellular carcinoma, hilar cholangiocarcinoma, and complications of portal hypertension. Not all patients are candidates for liver transplantation, and some will experience disease recurrence afterward.

If the condition does not improve, the risk of death is significant. In case of poor response to conservative therapy, a colectomy is usually required.

Possible treatments include:

- In stable cases, use of laxatives and bulking agents, as well as modifications in diet and stool habits are effective.

- Corticosteroids and other anti-inflammatory medication is used in toxic megacolon.

- Antibiotics are used for bacterial infections such as oral vancomycin for "Clostridium difficile"

- Disimpaction of feces and decompression using anorectal and nasogastric tubes.

- When megacolon worsens and the conservative measures fail to restore transit, surgery may be necessary.

- Bethanechol can also be used to treat megacolon by means of its direct cholinergic action and its stimulation of muscarinic receptors which bring about a parasympathetic like effect.

There are several surgical approaches to treat megacolon, such as a colectomy (removal of the entire colon) with ileorectal anastomosis (ligation of the remaining ileum and rectum segments), or a total proctocolectomy (removal of colon, sigmoid and rectum) followed by ileostomy or followed by ileoanal anastomosis.

Treatment for proctitis varies depending on severity and the cause. For example, the physician may prescribe antibiotics for proctitis caused by bacterial infection. If the proctitis is caused by Crohn's disease or ulcerative colitis, the physician may prescribe the drug 5-aminosalicyclic acid (5ASA) or corticosteroids applied directly to the area in enema or suppository form, or taken orally in pill form. Enema and suppository applications are usually more effective, but some patients may require a combination of oral and rectal applications.

Another treatment available is that of fiber supplements such as Metamucil. Taken daily these may restore regularity and reduce pain associated with proctitis.

Except in the most severe cases, ischemic colitis is treated with supportive care. IV fluids are given to treat dehydration, and the patient is placed on bowel rest (meaning nothing to eat or drink) until the symptoms resolve. If possible, cardiac function and oxygenation should be optimized to improve oxygen delivery to the ischemic bowel. A nasogastric tube may be inserted if an ileus is present.

Antibiotics are sometimes given in moderate to severe cases; the data supporting this practice date to the 1950s, although there is more recent animal data suggesting that antibiotics may increase survival and prevent bacteria from crossing the damaged lining of the colon into the bloodstream. The use of prophylactic antibiotics in ischemic colitis has not been prospectively evaluated in humans, but many authorities recommend their use based on the animal data.

Patients being treated supportively are carefully monitored. If they develop worsening symptoms and signs such as high white blood cell count, fever, worsened abdominal pain, or increased bleeding, then they may require surgical intervention; this usually consists of laparotomy and bowel resection.

Symptoms such as diarrhea and painful defecation need to be systematically investigated and the underlying causes each carefully treated. Complications such as obstruction and fistulae may require surgery. Several other methods have been studied in attempts to lessen the effects of radiation proctitis. These include sucralfate, hyperbaric oxygen therapy, corticosteroids, metronidazole, argon plasma coagulation, radiofrequency ablation and formalin irrigation.

A subtype of infectious colitis is "Clostridium difficile" colitis, which is informally abbreviated as "c diff colitis". It classically forms and is often referred to as pseudomembranous colitis, which is its (nonspecific) histomorphologic description.

Enterohemorrhagic colitis may be caused by Shiga toxin in "Shigella dysenteriae" or "Shigatoxigenic group" of "Escherichia coli" (STEC), which includes serotype and other enterohemorrhagic "E. coli".

Parasitic infections, like those caused by "Entamoeba histolytica", can also cause colitis.

Chemical colitis is a type of colitis, an inflammation of the large intestine or colon, caused by the introduction of harsh chemicals to the colon by an enema or other procedure. Chemical colitis can resemble ulcerative colitis, infectious colitis and pseudomembranous colitis endoscopically.

Prior to 1950, hydrogen peroxide enemas were commonly used for certain conditions. This practice will often result in chemical colitis.

Soap enemas may also cause chemical colitis.

Harsh chemicals, such as compounds used to clean colonoscopes, are sometimes accidentally introduced into the colon during colonoscopy or other procedures. This can also lead to chemical colitis.

Chemical colitis may trigger a flare of ulcerative colitis or Crohn's colitis. Symptoms of colitis are assessed using the Simple Clinical Colitis Activity Index.