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What the label lists and what reports show

Olsalazine side effects

Olsalazine's FDA label: “The most common adverse reactions leading to discontinuation in DIPENTUM-treated patients were diarrhea/loose stools (6%), abdominal pain (1%), and rash/itching (1%).” FAERS holds 197 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is colitis ulcerative (19 reports).

  • No generic listed

Check it at the source: the olsalazine FDA label on DailyMed (effective May 15, 2026, Viatris Specialty LLC); the FDA FAERS public dashboard.

What does the label list?

From the label: adverse reactions

The most common adverse reactions leading to discontinuation in DIPENTUM-treated patients were diarrhea/loose stools (6%), abdominal pain (1%), and rash/itching (1%).

Table 1 Adverse Reactions reported in at least 1% of patients in the DIPENTUM group and greater than placebo in Patients with Ulcerative Colitis in Double-Blind, Controlled Clinical Trials

Adverse ReactionDIPENTUM (N=441) %Placebo (N=208) %
Diarrhea117
Abdominal pain/cramps107
Nausea54
Arthralgia/Joint Pain43
Rash21
Upper Respiratory Infection20
Depression20
Vomiting10
Stomatitis10
Vertigo/Dizziness10
Itching10

Rows and numbers as the label prints them, under its own column headings (the first rows of a longer table where it runs on). A reaction in a trial table is not necessarily caused by the medicine, and trials differ from everyday use.

From the label: adverse reactions, continued

The following clinically significant adverse reactions are described elsewhere in the labeling: • Renal impairment [see Warnings and Precautions (5.1) ] • Mesalamine-induced acute intolerance syndrome [see Warnings and Precautions (5.2) ] • Hypersensitivity reactions [see Warnings and Precautions (5.3) ] • Hepatic failure [see Warnings and Precautions (5.4) ] • Severe cutaneous adverse reactions [see Warnings and Precautions (5.5) ] • Photosensitivity [see Warnings and Precautions (5.6) ] • Nephrolithiasis [see Warnings and Precautions (5.7) ] The following adverse reactions have been identified from clinical studies or postmarketing reports of olsalazine. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. In double-blind, placebo- and active-controlled clinical trials of ulcerative colitis, discontinuations due to adverse reactions were reported in 10% of DIPENTUM-treated patients (N=441) and 7% of placebo-treated patients (N=208). Both sulfasalazine-tolerant and intolerant patients were included. The most common adverse reactions leading to discontinuation in DIPENTUM-treated patients were diarrhea/loose stools (6%), abdominal pain (1%), and rash/itching (1%). …

Source: FDA drug label, Viatris Specialty LLC, effective May 15, 2026 (SPL set 8512d0c6-db4e-4673-b3b4-28975c18413f), via openFDA; the full label on DailyMed

What do FAERS reports show?

197 reports list olsalazine among the medicines taken, each a report of something that happened, not proof the medicine caused it; 11 are coded as a death and 69 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Of the 22 reactions below, 7 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.

The 25 most reported reactions

  • Colitis Ulcerative19
  • Diarrhoea (named in the label)14
  • Drug Ineffective (a use or a product term, not a reaction)12
  • Off Label Use (a use or a product term, not a reaction)11
  • Fatigue9
  • Pain8
  • Pain In Extremity7
  • Pruritus7
  • Pyrexia (named in the label)7
  • Abdominal Pain (named in the label)6
  • Anxiety6
  • Arthralgia (named in the label)6
  • Chest Pain (named in the label)6
  • Haematochezia6
  • Malaise6
  • Nausea (named in the label)6
  • Rash (named in the label)6
  • Cataract5
  • Colitis (a use or a product term, not a reaction)5
  • Cough5
  • Depression5
  • Headache5
  • Influenza Like Illness5
  • Neuropathy Peripheral5
  • Renal Failure Acute5

Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms

What next?

Olsalazine: the full record
label, generics, price, shortages, recalls
Side effects hub
the most reported medicines and reactions