The pill stamped “S111” (sometimes written “S 111”) is a round, blue tablet containing 10 mg of dicyclomine hydrochloride, a prescription antispasmodic medication. It is most commonly prescribed for irritable bowel syndrome and other conditions that involve painful cramping of the gastrointestinal tract. If you found one of these pills loose in a drawer or medicine cabinet, this article covers what it does, how well it works, what side effects to expect, and which groups of people should not take it.
Identifying the Pill
The imprint “S 111” appears on one side of a small, round, blue tablet. This marking identifies it as dicyclomine hydrochloride 10 mg. In the United States, every solid oral medication is required by federal regulation to carry a unique imprint so that pills can be identified even outside their original packaging. Each manufacturer chooses its own code, which is why pill identification can sometimes be confusing when different companies make the same drug with different stamps.
If you’re trying to verify a pill’s identity, the imprint alone is not always enough. Color, shape, and size matter too. Several online pill identifier tools maintained by pharmacies and the National Library of Medicine can cross-reference all of these features. When in doubt, a pharmacist can confirm the identity quickly and for free.
What Dicyclomine Does
Dicyclomine belongs to a class of drugs called anticholinergics, sometimes also referred to as antispasmodics. It works by blocking a chemical messenger called acetylcholine from activating certain receptors in the smooth muscle lining of the gut. This relaxes the muscle, which reduces the painful spasms and cramping that characterize conditions like irritable bowel syndrome. It does not cure the underlying condition or change the course of the disease; it manages symptoms, primarily pain and abnormal bowel habits.
The drug has been around for decades. It is sold under the brand name Bentyl in the United States, though most prescriptions are now filled with generic versions. The S111 tablet is one such generic formulation at the lowest commonly prescribed dose of 10 mg. Higher-strength capsules (20 mg) and an injectable form also exist, but the 10 mg tablet is often where doctors start, particularly when they want to see how a patient tolerates the medication before increasing the dose.
How Well It Works for IBS
The evidence supporting dicyclomine for IBS is generally positive but comes from older, relatively short trials. In a placebo-controlled study, dicyclomine at 40 mg taken four times daily was found to be better than placebo at reducing abdominal pain, decreasing tenderness, and improving bowel habits over a two-week period.1PubMed. Treatment of the irritable bowel syndrome with Bentyl (dicyclomine hydrochloride) That dose, 160 mg per day, is at the higher end of what is prescribed; someone starting on the S111 (10 mg) tablet would typically take a much lower daily total.
A broader analysis of antispasmodic treatment options available in North America confirmed that dicyclomine improved IBS symptoms relative to placebo across two randomized controlled trials, though both studies were short, lasting only ten days to two weeks.2PubMed Central. Antispasmodics for Chronic Abdominal Pain: Analysis of North American Treatment Options The short duration is a legitimate limitation. IBS is a chronic condition, and whether dicyclomine remains effective over months of use is less well established by rigorous trial data. In clinical practice, many doctors prescribe it on an as-needed basis rather than as a continuous daily therapy, which partly sidesteps the question of long-term efficacy.
Beyond IBS
While IBS is the best-known indication, dicyclomine is sometimes prescribed off-label for other types of abdominal cramping. One setting where it has been studied more recently is irritable pouch syndrome, a condition that can develop after surgical removal of the colon when a surgically created internal pouch begins causing IBS-like symptoms. In a retrospective study of patients with this condition, dicyclomine was the preferred treatment for abdominal pain, accounting for roughly two-thirds of treatment courses for that symptom. About 68% of those patients saw clinical improvement.3Crohn’s & Colitis 360. The efficacy and safety of hyoscyamine, dicyclomine, and desipramine in the treatment of irritable pouch syndrome—a retrospective cohort study Dicyclomine also showed the best long-term sticking power in that study, with nearly half of patients remaining on it for three years or longer. That persistence suggests patients find it tolerable and useful enough to keep taking, even if randomized trial data are limited to short windows.
Common Side Effects
Because dicyclomine blocks acetylcholine, its side effects are largely predictable from that mechanism. Acetylcholine does a lot of things throughout the body beyond contracting gut muscle: it stimulates saliva production, keeps the eyes focused at close range, promotes sweating, and helps the bladder contract. Blocking it can therefore cause dry mouth, blurred vision, dizziness, drowsiness, and difficulty urinating. These are the classic “anticholinergic” side effects shared by many drugs in the same family.
At lower doses, these effects are generally mild. In the irritable pouch syndrome study mentioned earlier, no single adverse event occurred in more than 3% of the dicyclomine-treated group.4Crohn’s & Colitis 360. The efficacy and safety of hyoscyamine, dicyclomine, and desipramine in the treatment of irritable pouch syndrome—a retrospective cohort study However, at higher doses the picture changes. In one of the original IBS trials, 69% of patients taking 160 mg per day reported side effects, compared with only 16% of those taking placebo.5PubMed Central. Antispasmodics for Chronic Abdominal Pain: Analysis of North American Treatment Options This dose-dependent relationship is worth keeping in mind. Someone starting on a single 10 mg S111 tablet is far less likely to experience bothersome effects than someone taking four 40 mg doses. If side effects are a concern, it is reasonable to ask your doctor about staying at the lowest effective dose and using the medication as needed rather than on a fixed schedule.
Risks for Older Adults
Anticholinergic drugs as a class pose particular concerns for older adults. The American Geriatrics Society’s Beers Criteria, a widely used list of medications considered potentially inappropriate for people over 65, includes dicyclomine. The reasoning is straightforward: older adults are more sensitive to the cognitive effects of anticholinergic drugs, including confusion, memory impairment, and sedation, and they are at greater risk of falls. Analysis of adverse drug event risk in the U.S. geriatric population found that dicyclomine-related dizziness, blurred vision, and dry mouth represented a notable source of preventable harm.6PLOS ONE. South Korean geriatrics on Beers Criteria medications at risk of adverse drug events
This does not mean no older adult should ever take dicyclomine, but it does mean the risk-benefit calculation shifts. A younger adult experiencing cramping from IBS may find the mild dry mouth a worthwhile tradeoff. For an 80-year-old who already has mild cognitive impairment and a history of falls, the same drug could be genuinely dangerous. If you are over 65 or caring for someone who is, it is worth asking the prescribing doctor whether a non-anticholinergic alternative has been considered.
Why It Should Not Be Given to Infants
Dicyclomine was once used to treat colic in infants, but that practice has been abandoned after reports of serious harm. The drug is now contraindicated in children younger than six months. Case reports documented respiratory distress and death in infants who received as little as one or two oral doses. In one case, a very low dose of roughly 0.5 to 1 mg still triggered respiratory distress in an infant.7Journal of Pharmacy Technology. Low Dose of Dicyclomine Associated with Respiratory Distress and Death in an Infant The mechanism likely involves the drug’s suppression of the respiratory drive combined with the immature respiratory system of a very young infant. This is one of the clearest and most dangerous contraindications for dicyclomine, and any parent who is offered the drug for a baby’s colic should know the history.
For children older than six months, some prescribers do use dicyclomine, but the evidence base for pediatric use is thin and the safety margins are tighter than in adults. Pediatric dosing, when it occurs, is weight-based and done cautiously.
How Dicyclomine Compares to Other Antispasmodics
In North America, the other common antispasmodic for IBS is hyoscyamine, sold under brand names like Levsin. Both drugs work through the same basic mechanism of blocking acetylcholine, though they differ in pharmacology, dosing, and how long they stay active in the body. In the irritable pouch syndrome study, dicyclomine was preferred for abdominal pain (used in about 64% of pain-related treatment courses), while hyoscyamine was more commonly chosen for high bowel frequency.8Crohn’s & Colitis 360. The efficacy and safety of hyoscyamine, dicyclomine, and desipramine in the treatment of irritable pouch syndrome—a retrospective cohort study The improvement rates were broadly similar across the two drugs, hovering in the 60–70% range for their respective indications.
Outside North America, other antispasmodics such as mebeverine, otilonium bromide, and pinaverium bromide are available and have a larger body of trial data. If you’ve read about IBS treatments used in Europe or Asia and wondered why they aren’t offered here, it is largely a regulatory issue rather than a safety one.
Another category sometimes used for IBS symptoms is low-dose tricyclic antidepressants like desipramine. In the same irritable pouch syndrome cohort, desipramine actually had the highest improvement rate for abdominal pain at about 76%, though it was used in fewer treatment courses. Desipramine has its own anticholinergic side effects, so it is not necessarily gentler, but it addresses both pain and mood, which can be relevant for IBS patients who also have depression or anxiety.
Abuse Potential and Anticholinergic Toxicity
Dicyclomine is not a controlled substance and is not considered addictive in the way that opioids or benzodiazepines are. However, rare cases of misuse have been documented. One published case report described an 18-year-old who abused dicyclomine for a year and a half, developing overt signs of anticholinergic toxicity.9PubMed Central. A rare case of dicyclomine abuse Anticholinergic toxicity at high doses can include hallucinations, agitation, rapid heart rate, urinary retention, dangerously high body temperature, and seizures. The syndrome is sometimes summarized with the old medical mnemonic: “hot as a hare, blind as a bat, dry as a bone, red as a beet, mad as a hatter.”
The reason someone might misuse an anticholinergic is that at high doses, these drugs can produce a delirium with hallucinatory features. Unlike the hallucinations from classic psychedelics, anticholinergic hallucinations tend to be dysphoric and disorienting rather than visually vivid, which is why this form of abuse is uncommon. Still, if you have the S111 pill in your home and there are teenagers or others who might experiment with it, it is worth storing it out of easy reach, just as you would with any medication.
Practical Tips for Taking the S111 Pill
If you’ve been prescribed this tablet, a few practical points are worth keeping in mind. The drug works best when taken about 30 minutes before meals, since its purpose is to preemptively calm the gut before food triggers spasms. It can also be taken at bedtime if nighttime cramping is a problem. Starting at 10 mg (one S111 tablet) and increasing gradually gives your body time to adjust and helps you find the lowest dose that controls your symptoms.
Because dicyclomine can cause drowsiness and blurred vision, it makes sense to see how it affects you before driving or doing anything requiring sharp focus. Alcohol amplifies these effects, so pairing the two is a bad idea. Heat intolerance is another underappreciated effect: by suppressing sweating, anticholinergics can make you overheat more easily during exercise or in hot weather. If you find yourself unusually flushed or unable to cool down, that could be the medication.
Stopping dicyclomine abruptly after taking it regularly for a while is generally fine and does not cause a withdrawal syndrome, but some people notice a temporary rebound of cramping. Tapering off over a few days can smooth that transition if it happens to you.
When Pill Identification Matters Most
The scenario that leads most people to search for “S111 pill” is finding an unidentified tablet. Pill identification is more than a curiosity exercise; it has real safety implications. Accidentally taking someone else’s medication, or a child swallowing a pill found on the floor, requires knowing what the substance is so that the appropriate response can happen quickly. The current system of pill imprints in the United States relies on each manufacturer choosing its own codes, which means there is no universal logic to how markings are assigned.10PubMed Central. Standardized pill imprint codes: a pharma fantasy Two pills from different manufacturers can look nearly identical apart from a subtle font difference in the imprint.
For a confirmed S111 tablet specifically, the risk profile in an accidental exposure depends heavily on who swallowed it. A healthy adult who takes a single 10 mg dicyclomine tablet by mistake is unlikely to experience more than mild dry mouth or drowsiness. An infant or a very small child is a different story entirely, given the respiratory risks described above. In any case of accidental ingestion involving a child under six months, poison control (1-800-222-1222 in the U.S.) should be contacted immediately.