Dicyclomine

What it is

Dicyclomine is a synthetic antispasmodic drug, known outside the United States as dicycloverine. It is given as a tablet, capsule, oral solution or intramuscular injection, and it is prescription-only. In the body it blocks muscarinic acetylcholine receptors and, separately, relaxes gut smooth muscle directly. By weight it is roughly one eighth as potent as atropine at acetylcholine receptors in isolated guinea-pig ileum, and far weaker than atropine on the pupil and on saliva.

What the research says

Dicyclomine is approved in the United States for one thing only: functional bowel or irritable bowel syndrome. The approval rests largely on a single two-week trial from 1981 in which 82% of patients on 40 mg four times a day had a favourable response against 55% on placebo, and in which 61% of patients reported anticholinergic side effects. Cochrane found antispasmodics as a class help abdominal pain and global symptoms, with dicyclomine among the subgroups that reached statistical significance, but the 2011 review did not assess adverse events at all and a 2020 network meta-analysis could not separate any active treatment from the others. The harms are the predictable anticholinergic ones, and they are frequent at the licensed starting dose. It is contraindicated in infants under six months and in breastfeeding women.

Evidence grade: Limited evidence.

How it works

Drug class: Antimuscarinic (anticholinergic) antispasmodic with an additional direct smooth-muscle relaxant action

Dicyclomine relaxes the muscle in the wall of the gut by two routes: it blocks acetylcholine from acting on muscarinic receptors there, and it also acts directly on the smooth muscle itself, blocking spasms triggered by bradykinin and histamine, which atropine does not do. Because muscarinic receptors are everywhere, the same blockade produces dry mouth, blurred vision, a fast heart rate, difficulty passing urine and constipation. It is absorbed quickly by mouth, peaking at 60 to 90 minutes, with a plasma half-life of about 1.8 hours in one study. (Source 1)

What it is used for

• The only approved use. One 1981 trial of over 100 patients at 160 mg a day for two weeks reported 82% favourable response against 55% on placebo. A Cochrane review found cimetropium/dicyclomine among the antispasmodic subgroups with a statistically significant benefit, and a 2008 meta-analysis put the single dicycloverine trial at a relative risk of persistent symptoms of 0.65 (0.45 to 0.95). A 2020 network meta-analysis could not show any antispasmodic superior to the others. Evidence: limited. (Source 2)
• No longer used. Dicyclomine is contraindicated in infants under six months, and the label records published cases of serious respiratory symptoms, seizures, coma and death in infants given it, with blood levels reported in three infants who died. Evidence: not-supported. (Source 3)

Interactions

• Antacids, including calcium carbonate and magnesium hydroxide products (label): Antacids can block dicyclomine’s own absorption, so the label says not to take them at the same time. This matters for anyone taking a calcium antacid for reflux. (Source 4)
• Digoxin (slowly dissolving forms) (theoretical): By slowing the gut, dicyclomine can let slowly dissolving digoxin tablets be absorbed more completely, raising blood levels of a drug with a narrow safety margin. (Source 4)
• Antihistamines, tricyclic antidepressants, phenothiazines (including promethazine), benzodiazepines, amantadine, class I antiarrhythmics and opioid analgesics (label): Each of these adds to dicyclomine’s drying and sedating effects. The combined anticholinergic load is what produces confusion and delirium, especially in older people. (Source 5)
• Alcohol (label): No specific dicyclomine-alcohol interaction is documented in the sources we reached. The label does warn that the drug itself may cause drowsiness, dizziness or blurred vision and that patients should not drive or do hazardous work while taking it, which alcohol would compound. (Source 6)
• Breast milk (passage to the infant) (label): Dicyclomine passes into human milk and is contraindicated while breastfeeding because of the risk of serious reactions in the infant. (Source 7)
• Hot weather and exercise (label): Not a dietary interaction but worth naming here: by cutting sweating, dicyclomine can cause heat prostration, fever and heat stroke in high environmental temperatures. (Source 6)

Stopping it

• There is no withdrawal syndrome described for dicyclomine in any source we reached, and the label gives no taper. Its stopping instructions run the other way: stop at two weeks if it has not worked, or if side effects force the dose below 80 mg a day. (Source 8)
• Confusion, disorientation, hallucinations and other central effects usually clear within 12 to 24 hours of stopping the drug, which is one reason stopping is the first step when they appear. (Source 6)
• In one reported overdose at 320 mg a day - four 20 mg tablets four times daily - the symptoms resolved after the dicyclomine was stopped. The same section of the label says that if indicated an appropriate parenteral cholinergic agent may be used as an antidote. (Source 9)

What goes wrong

Antispasmodics caused significantly more adverse events than placebo in the 2008 meta-analysis, with a number needed to harm of 17.5, though none of the events was serious. (Source 10)

• Meta-analysis, Low certainty.
• Size: 13 studies, 1,379 patients.
• Who: adults with irritable bowel syndrome taking antispasmodics or placebo.
• How long: varied by trial.
• Result: 101 of 704 (14%) on antispasmodics had adverse events versus 62 of 675 (9%) on placebo; relative risk 1.62 (95% CI 1.05 to 2.50); number needed to harm 17.5 (7.0 to 217.0). Commonest were dry mouth, dizziness and blurred vision.
• Funding: independent.

Limit of this finding: One figure in this paragraph contradicts itself: the authors write that heterogeneity between studies was statistically significant at I2=37.9%, P=0.07, but a P of 0.07 is above the 0.05 threshold the same paper uses elsewhere. That is the paper's inconsistency, not a transcription error. It does not change the harm estimate - 14% versus 9% of patients with adverse events, relative risk 1.62 (1.05 to 2.50) - but it means the claim that the trials disagreed with each other should be read as uncertain, and none of the reported events was serious.

Overall, 101 of 704 (14%) patients assigned to antispasmodics experienced adverse events compared with 62 of 675 (9%) allocated to placebo. The commonest adverse events were dry mouth, dizziness, and blurred vision, but none of the trials reported any serious adverse events. The relative risk of experiencing adverse events with antispasmodics compared with placebo was 1.62 (95% confidence interval 1.05 to 2.50), with statistically significant heterogeneity detected between studies (I2=37.9%, P=0.07), but no evidence of publication bias (Egger test, P=0.53). The number needed to harm with antispasmodics was 17.5 (7.0 to 217.0).

In the trials behind approval, run at 160 mg a day - double the 20 mg four times a day the same label sets as the starting dose - 61% of patients had anticholinergic side effects and 9% stopped the drug because of them, against 2% on placebo. (Source 11)

• Randomized trial, Moderate certainty.
• Size: over 100 patients in controlled clinical trials.
• Who: patients treated for functional bowel/irritable bowel syndrome at initial doses of 160 mg daily (40 mg four times a day)
• How long: not stated in the label section.
• Result: From the label's section 6.1 Clinical Trials Experience and its Table 1: side effects reported by 61% of patients. Dicyclomine versus placebo in that table: dizziness 40% versus 5%, dry mouth 33% versus 5%, blurred vision 27% versus 2%, nausea 14% versus 6%, somnolence 9% versus 1%, asthenia 7% versus 1%, nervousness 6% versus 2%. Discontinuation 9% versus 2%. In 41% of those with side effects the effects disappeared or were tolerated at 160 mg a day; 46% needed a cut to an average of 90 mg a day and then kept a favourable response.
• Funding: industry-funded (manufacturer trials submitted for approval)

Limit of this finding: Every rate here comes from trials that started people on 160 mg a day (40 mg four times a day). Section 2.1 of the same label sets the recommended starting dose at 20 mg four times a day, 80 mg a day, rising to 40 mg four times a day only after a week if it is tolerated and needed. So 61% is the side-effect rate at double the starting dose, not the rate someone beginning dicyclomine faces. The label also states its own limit on these figures: rates seen in trials cannot be compared with another drug's trials and may not reflect the rates seen in practice.

In these trials most of the side effects were typically anticholinergic in nature and were reported by 61% of the patients. Table 1 presents adverse reactions (MedDRA 13.0 preferred terms) by decreasing order of frequency in a side-by-side comparison with placebo. Table 1: Adverse reactions experienced in controlled clinical trials with decreasing order of frequency MedDRA Preferred Term | Dicyclomine Hydrochloride (40 mg four times a day) | Placebo | | % | % | Dry Mouth | 33 | 5 | Dizziness | 40 | 5 | Vision blurred | 27 | 2 | Nausea | 14 | 6 | Somnolence | 9 | 1 | Asthenia | 7 | 1 | Nervousness | 6 | 2 | Nine percent (9%) of patients were discontinued from dicyclomine hydrochloride because of one or more of these side effects (compared with 2% in the placebo group).

The label warns that dicyclomine can cause confusion, hallucinations, psychosis and delirium, particularly in older people and people with mental illness, and that these usually clear 12 to 24 hours after stopping. (Source 6)

• Official position, Certainty not rated.
• Size: not stated.
• Who: patients taking dicyclomine, with sensitive individuals such as elderly patients singled out.
• How long: resolution usually within 12 to 24 hours of stopping.
• Result: No rates given in the label for the central nervous system effects.
• Funding: not stated.

Central nervous system (CNS) signs and symptoms include confusional state, disorientation, amnesia, hallucinations, dysarthria, ataxia, coma, euphoria, fatigue, insomnia, agitation and mannerisms, and inappropriate affect. Psychosis and delirium have been reported in sensitive individuals (such as elderly patients and/or in patients with mental illness) given anticholinergic drugs. These CNS signs and symptoms usually resolve within 12 to 24 hours after discontinuation of the drug.

Delirium, transient global amnesia, hallucinations, mania and pseudodementia have been reported with dicyclomine after marketing, as with other anticholinergic drugs. (Source 12)

• Official position, Very low certainty.
• Size: spontaneous reports from a population of uncertain size.
• Who: patients taking dicyclomine after approval.
• How long: not stated.
• Result: Frequency cannot be estimated from these reports, as the label itself states.
• Funding: not stated.

Limit of this finding: These are spontaneous reports collected after the drug was on the market. The label states plainly that because they come from a population of uncertain size, it is not always possible to estimate how often they happen or to establish that the drug caused them. No rate can be read off this list.

cases of delirium or symptoms of delirium such as amnesia (or transient global amnesia), agitation, confusional state, delusion, disorientation, hallucination (including visual hallucination) as well as mania, mood altered and pseudodementia, have been reported with the use of dicyclomine.

Dicyclomine is contraindicated in infants under six months and in breastfeeding women; published cases describe infants developing apnoea, seizures, coma and death after being given it. (Source 3)

• Case series, Very low certainty.
• Size: published cases; the label reports blood concentrations in three infants who died.
• Who: infants given dicyclomine.
• How long: not stated.
• Result: Blood concentrations in three infants who died were 200, 220 and 505 ng/mL. The label states no causal relationship has been established.
• Funding: not stated.

There are published cases reporting that the administration of dicyclomine hydrochloride to infants has been followed by serious respiratory symptoms (dyspnea, shortness of breath, breathlessness, respiratory collapse, apnea and asphyxia), seizures, syncope, pulse rate fluctuations, muscular hypotonia, and coma, and death, however; no causal relationship has been established.

Given into a vein by mistake, the injectable form can cause clots, vein inflammation and reflex sympathetic dystrophy; it is licensed for intramuscular use only. (Source 13)

• Official position, Certainty not rated.
• Size: not stated.
• Who: patients given dicyclomine injection.
• How long: not applicable.
• Result: No rates are given. This section restricts the solution to intramuscular use and says any other route is not to be used; the injury types listed are the label's own.
• Funding: not stated.

Inadvertent intravenous administration may result in thrombosis, thrombophlebitis, and injection site reactions such as pain, edema, skin color change, and reflex sympathetic dystrophy syndrome

The label lists the ordinary peripheral consequences of blocking muscarinic receptors: dry mouth with difficulty swallowing and talking, dilated pupils with loss of focus and light sensitivity, flushing, a slow then fast heart rate with palpitations and arrhythmias, difficulty passing urine, and constipation. (Source 14)

• Official position, Certainty not rated.
• Size: not stated.
• Who: patients taking dicyclomine.
• How long: not applicable.
• Result: No rates are given in this section of the label; the rates against placebo appear in the adverse reactions table.
• Funding: not stated.

They include dryness of the mouth with difficulty in swallowing and talking, thirst, reduced bronchial secretions, dilatation of the pupils (mydriasis) with loss of accommodation (cycloplegia) and photophobia, flushing and dryness of the skin, transient bradycardia followed by tachycardia, with palpitations and arrhythmias, and difficulty in micturition, as well as reduction in the tone and motility of the gastrointestinal tract leading to constipation

What the evidence supports

In the controlled trials that supported approval, 82% of patients given dicyclomine at 160 mg a day - double the label's own starting dose - had a favourable clinical response for functional bowel/irritable bowel syndrome, against 55% on placebo. (Source 2)

• Randomized trial, Low certainty.
• Size: over 100 patients who received drug.
• Who: patients with functional bowel/irritable bowel syndrome.
• How long: the pivotal trial ran 2 weeks.
• Result: 82% favourable response on dicyclomine 160 mg daily (40 mg four times daily) versus 55% on placebo (p<0.05); an absolute difference of 27 percentage points as the label reports it.
• Funding: industry-funded (manufacturer trials submitted for approval)

Limit of this finding: The 82% figure is the response at 160 mg a day (40 mg four times a day). The same label starts people at 20 mg four times a day and only moves to 160 mg a day after a week, so this is not the response rate at a starting dose. Note too that 55% of placebo patients were also judged to have a favourable response, and the only effect measure the label gives is p<0.05.

In controlled clinical trials involving over 100 patients who received drug, 82% of patients treated for functional bowel/irritable bowel syndrome with dicyclomine hydrochloride at initial doses of 160 mg daily (40 mg four times daily) demonstrated a favorable clinical response compared with 55% treated with placebo (p<0.05).

Cochrane found antispasmodics as a class better than placebo for abdominal pain and global symptoms in irritable bowel syndrome; the subgroup that reached significance pools cimetropium and dicyclomine together, so it is not dicyclomine-specific evidence. (Source 15)

• Systematic review, Moderate certainty.
• Size: 1,392 patients across 13 trials for abdominal pain; 1,983 across 22 trials for global assessment (56 studies, 3,725 patients in the whole review)
• Who: patients over 12 years of age with irritable bowel syndrome.
• How long: varied by trial.
• Result: Abdominal pain improved in 58% on antispasmodics versus 46% on placebo (RR 1.32, 95% CI 1.12 to 1.55, P<0.001, NNT 7); global assessment 57% versus 39% (RR 1.49, 95% CI 1.25 to 1.77, P<0.0001, NNT 5); symptom score 37% versus 22% (RR 1.86, 95% CI 1.26 to 2.76, P<0.01, NNT 3).
• Funding: independent.

Limit of this finding: The significant subgroup is cimetropium and dicyclomine pooled - the review reports no dicyclomine-only subgroup, so none of these figures is a dicyclomine result. The review's abstract prints the pooled subgroup as "cimteropium/ dicyclomine" in its results and "cimetropium/dicyclomine" in its conclusions; the first spelling is a misspelling in the source and is quoted as printed. The searches ran to 2009, so the 2011 date is the publication year, not the evidence cut-off, and a 2011 update identified ten further studies that were left to a later version.

There was a beneficial effect for antispasmodics over placebo for improvement of abdominal pain (58% of antispasmodic patients improved compared to 46% of placebo; 13 studies; 1392 patients; RR 1.32; 95% CI 1.12 to 1.55; P < 0.001; NNT = 7), global assessment (57% of antispasmodic patients improved compared to 39% of placebo; 22 studies; 1983 patients; RR 1.49; 95% CI 1.25 to 1.77; P < 0.0001; NNT = 5) and symptom score (37% of antispasmodic patients improved compared to 22% of placebo; 4 studies; 586 patients; RR 1.86; 95% CI 1.26 to 2.76; P < 0.01; NNT = 3). Subgroup analyses for different types of antispasmodics found statistically significant benefits for cimteropium/ dicyclomine, peppermint oil, pinaverium and trimebutine.

In a 2008 meta-analysis the single dicycloverine (dicyclomine) trial gave a relative risk of persistent irritable bowel symptoms of 0.65, with a confidence interval only just excluding no effect. (Source 16)

• Meta-analysis, Low certainty.
• Size: 1 trial of 97 patients within a pooled set of 22 antispasmodic trials in 1,778 patients.
• Who: adults with irritable bowel syndrome.
• How long: 2 weeks for the dicycloverine trial.
• Result: Dicycloverine relative risk of persistent symptoms 0.65 (0.45 to 0.95). For comparison, mebeverine 1.25 (0.99 to 1.58) and trimebutine 1.08 (0.72 to 1.61) showed no benefit.
• Funding: independent.

Limit of this finding: The dicycloverine (dicyclomine) figure here rests on one trial, the 1981 Page trial also cited in this write-up, not on a body of trials. Four of the seven single-drug estimates in the same sentence cross 1, so the review is not showing that antispasmodics work individually; it is reporting what each single trial found.

The relative risk of persistent symptoms in the single trials that used other antispasmodics were: mebeverine 1.25 (0.99 to 1.58), alverine 0.85 (0.60 to 1.22), dicycloverine 0.65 (0.45 to 0.95), pirenzipine 1.17 (0.56 to 2.45), prifinium 0.50 (0.18 to 1.40), propinox 1.23 (0.30 to 5.13), and rociverine 1.10 (0.55 to 2.19).

What the evidence does not support

A 2020 network meta-analysis of 51 trials of antispasmodics as a class, together with fibre, peppermint oil and gut-brain neuromodulators, could not show any of these treatments better than another for irritable bowel syndrome, and only 13 of the trials were at low risk of bias; the record does not name dicyclomine among the trials it pooled. (Source 17)

• Meta-analysis, Low certainty.
• Size: 51 RCTs, 4,644 patients.
• Who: adults aged at least 18 with irritable bowel syndrome of any subtype.
• How long: 4 to 12 weeks of treatment.
• Result: Peppermint oil ranked first for global symptoms (RR 0.63, 95% CI 0.48 to 0.83, P-score 0.84) and tricyclic antidepressants second (0.66, 0.53 to 0.83, P-score 0.77); for global symptoms at 4-12 weeks there were no significant differences between active treatments after direct or indirect comparison.
• Funding: independent (funding: None)

Limit of this finding: This is evidence about antispasmodics as a drug class, not about dicyclomine in particular. The record we quote never names dicyclomine, and it does not say which antispasmodic trials were pooled, so nothing here measures this drug. Read it as showing that no one class of irritable-bowel treatment outranked the others in this network, on trials most of which were not at low risk of bias.

For failure to achieve an improvement in global IBS symptoms at 4-12 weeks, there were no significant differences between active treatments after direct or indirect comparisons. For failure to achieve improvement in abdominal pain at 4-12 weeks, tricyclic antidepressants were ranked first for efficacy (0·53, 0·34-0·83, P-score 0·87); however, this result was based on data from only four RCTs involving 92 patients. For failure to achieve an improvement in abdominal pain, none of the active treatments showed superior efficacy upon indirect comparison.

Where the evidence is mixed

The 1981 trial behind the approval ran for only two weeks, judged response by physician and patient global ratings, and reported that most adverse effects were anticholinergic. (Source 18)

• Randomized trial, Low certainty.
• Size: 97 patients as counted by a later meta-analysis.
• Who: an ambulatory population with recent irritable bowel syndrome.
• How long: 2 weeks, double-blind.
• Result: No numerical effect estimate is given in the abstract; the conclusion is that dicyclomine 40 mg four times a day is superior to placebo on overall condition, abdominal pain, abdominal tenderness and bowel habit.
• Funding: not stated.

Limit of this finding: The abstract of this trial reports no sample size, no effect size and no p-values - only the authors' conclusion. The patient count of 97 comes from the later meta-analysis that pooled it. Nothing here supports a figure for how much better than placebo dicyclomine was.

It was concluded that over a 2-week period dicyclomine hydrochloride 40 mg 4 times a day is superior to placebo in improving the overall condition of the patient, decreasing abdominal pain, decreasing abdominal tenderness, and improving bowel habits. The majority of adverse effects reported were related to the anti-cholinergic activity of the drug.

That same Cochrane review did not look at adverse events at all, so its favourable conclusion about antispasmodics says nothing about their harms. (Source 19)

• Systematic review, Moderate certainty.
• Size: 56 studies, 3,725 patients.
• Who: patients over 12 with irritable bowel syndrome.
• How long: varied.
• Result: Not applicable - the outcome was not measured.
• Funding: independent.

Limit of this finding: Two things sit side by side in this review and must stay together: it concludes that antispasmodics are effective, and it did not assess adverse events at all. Its favourable conclusion therefore says nothing about safety. The subgroup it names as effective pools cimetropium with dicyclomine rather than testing dicyclomine on its own.

Adverse events were not assessed as an outcome in this review. Authors' conclusions There is no evidence that bulking agents are effective for treating IBS. There is evidence that antispasmodics are effective for the treatment of IBS.

None of the 22 antispasmodic trials in that meta-analysis reported how they concealed allocation, and the dicycloverine evidence is a single two-week trial. (Source 20)

• Meta-analysis, Low certainty.
• Size: 22 studies, 1,778 patients.
• Who: adults with irritable bowel syndrome.
• How long: from 1 week to 6 months across trials.
• Result: Not applicable - this is a quality judgement, not an effect estimate.
• Funding: independent.

None of the trials reported the method of allocation concealment. Four trials used otilonium,w16 w23 w25 w26 three cimetropium,w11-w13 three hyoscine,w10 w33 w35 three pinaverium,w22 w24 w27 two trimebutine,w15 w20 one trimebutine and rociverine,w14 and one each of alverine,w18 dicycloverine (dicyclomine),w21

The same authors warn that because most of the trials lacked methodological rigour and ran only 4 to 12 weeks, the long-term relative efficacy of these treatments is unknown. (Source 21)

• Meta-analysis, Low certainty.
• Size: 51 RCTs, 4,644 patients.
• Who: adults with irritable bowel syndrome.
• How long: 4 to 12 weeks in most trials.
• Result: Not applicable - a statement about certainty, not an effect.
• Funding: independent (funding: None)

because of the lack of methodological rigour of some RCTs analysed in our study, there is likely to be considerable uncertainty around these findings. In addition, because treatment duration in most included trials was 4-12 weeks, the long-term relative efficacy of these treatments is unknown.

Where the research disagrees

Whether dicyclomine specifically works for irritable bowel syndrome, or only antispasmodics as a loose class

• Ruepert and colleagues, Cochrane 2011, systematic review and meta-analysis of 56 randomised trials, adverse events not assessed; the cimetropium/dicyclomine subgroup is pooled, not dicyclomine alone: There is evidence that antispasmodics are effective for the treatment of IBS. The individual subgroups which are effective include: cimetropium/dicyclomine, peppermint oil, pinaverium and trimebutine. (Source 19)
• Black and colleagues, Lancet Gastroenterology & Hepatology 2020, network meta-analysis of 51 randomised trials of fibre, antispasmodics, peppermint oil and gut-brain neuromodulators, only 13 at low risk of bias; the record does not name dicyclomine among the trials pooled: peppermint oil was ranked first for efficacy when global symptoms were used as the outcome measure, and tricyclic antidepressants were ranked first for efficacy when abdominal pain was used as the outcome measure. However, because of the lack of methodological rigour of some RCTs analysed in our study, there is likely to be considerable uncertainty around these findings (Source 21)

How much

• Reference intake: Dosing is set by the prescriber. As a position, the FDA label (Lannett Company tablet and capsule label, effective 6 August 2026) gives a recommended initial dose of 20 mg four times a day, which may be increased after one week to 40 mg four times a day unless side effects prevent it. (Source 8)
• Upper limit: The same label sets 80 mg per day over two weeks as the edge of the evidence: it states that documented safety data are not available for doses above 80 mg daily for periods longer than 2 weeks, and that the drug should be stopped if efficacy is not achieved within 2 weeks or if side effects force doses below 80 mg a day. (Source 8)
• Studied: The approval trials gave 160 mg a day (40 mg four times a day) for the first two weeks, which is double the label's own recommended starting dose of 20 mg four times a day; 46% of those with side effects needed a cut to an average of 90 mg a day. (Source 11)
• Studied: Page 1981 gave Bentyl (dicyclomine hydrochloride) 40 mg four times daily for two weeks, double-blind against placebo. (Source 18)
• Studied: The injection label gives 10 mg to 20 mg four times a day intramuscularly, for 1 or 2 days only when oral medication cannot be taken. (Source 13)

A common belief, and what the research shows

The belief: Dicyclomine is a gentle antispasmodic you can take long term for irritable bowel syndrome.

What the research shows: The licensed dose is not gentle and the evidence does not stretch past a fortnight. In the approval trials "most of the side effects were typically anticholinergic in nature and were reported by 61% of the patients", and the label says plainly that "Documented safety data are not available for doses above 80 mg daily for periods longer than 2 weeks." A 2008 meta-analysis put the number needed to harm for antispasmodics at 17.5 (7.0 to 217.0).

Questions and answers

What is it?

Dicyclomine, sold as Bentyl and known as dicycloverine outside the United States, is a prescription antispasmodic. It comes as tablets, capsules, an oral solution and an intramuscular injection. Chemically it is an antimuscarinic drug, about one eighth as potent as atropine at acetylcholine receptors in isolated gut tissue. (Source 1)

What does it do in the body?

It relaxes the muscle in the gut wall in two ways: by blocking acetylcholine at muscarinic receptors, and by acting directly on the smooth muscle, which blocks spasms that atropine does not touch. That is meant to ease the cramping pain of irritable bowel syndrome. (Source 1)

Is it good or bad for you?

Both, in the same dose. At the licensed 160 mg a day, 82% of patients in the approval trials had a favourable response against 55% on placebo, but 61% had anticholinergic side effects and 9% stopped because of them against 2% on placebo. It is dangerous in specific groups: infants under six months, breastfeeding women, and people with glaucoma, myasthenia gravis, bowel obstruction or severe ulcerative colitis. (Source 22)

How do you get more of it?

It is prescription-only; there is no food or supplement source and no over-the-counter form. Absorption is quick by mouth, peaking at 60 to 90 minutes, and the intramuscular injection is about twice as bioavailable as the oral forms. Taking an antacid at the same time can reduce absorption. (Source 23)

If it is harmful, what reduces it?

Stopping the drug is the main step: the central nervous system effects usually resolve within 12 to 24 hours of discontinuation, and about four fifths of a dose leaves in the urine with a plasma half-life around 1.8 hours in one study. In overdose the label describes gastric lavage, emetics and activated charcoal, with a cholinergic agent as an antidote if needed. It is not known whether dicyclomine can be dialysed. (Source 23)

Why might someone be low in it or missing it?

Nobody is deficient in dicyclomine; the body neither makes nor needs it. People do not take it, or are taken off it, when it is contraindicated, when two weeks have passed without benefit, or when anticholinergic side effects force the dose too low to work. (Source 8)

Which whole foods contain it or feed it?

No food contains dicyclomine. It is a manufactured antimuscarinic drug. The only dietary point in the label is the reverse direction: antacids may interfere with its absorption, so they should not be taken at the same time. (Source 4)

We searched: We searched PubMed via E-utilities and Europe PMC for dicyclomine with food, dietary and nutrient terms, and read the full FDA label including description, clinical pharmacology, drug interactions and patient counselling; nothing describes a food source.

What happens if you do not have it?

Nothing is lost physiologically. Someone who stops it may get their cramping symptoms back, but the trials put the size of what is lost in perspective: in the approval trials 55% of placebo patients also had a favourable response, and a 2020 network meta-analysis could not show antispasmodics as a class to be better than the alternatives for irritable bowel syndrome. (Source 17)

How can you test for it?

There is no routine test to guide dicyclomine treatment and no monitoring blood level. Blood concentrations have been measured in research and in fatal infant cases, where the label records levels of 200, 220 and 505 ng/mL, but this is forensic rather than clinical testing. In practice the drug is judged by symptoms over the first two weeks. (Source 9)

References

1. DailyMed, US National Library of Medicine (Structured Product Label). Dicyclomine Hydrochloride - CLINICAL PHARMACOLOGY, Mechanism of Action (FDA label). 2026. Read the source
2. DailyMed, US National Library of Medicine (Structured Product Label). Dicyclomine Hydrochloride Tablets and Capsules - CLINICAL STUDIES (FDA label). 2026. Read the source
3. DailyMed, US National Library of Medicine (Structured Product Label). Dicyclomine Hydrochloride - USE IN SPECIFIC POPULATIONS, Pediatric Use (FDA label). 2026. Read the source
4. DailyMed, US National Library of Medicine (Structured Product Label). Dicyclomine Hydrochloride Capsules and Tablets, USP label - 7 DRUG INTERACTIONS: 7.4 Effect of Antacids, 7.5 Effect on Absorption of Other Drugs, 7.6 Effect on Gastric Acid Secretion. 2026. Read the source
5. DailyMed, US National Library of Medicine (Structured Product Label). Dicyclomine Hydrochloride - DRUG INTERACTIONS, Other Drugs with Anticholinergic Activity (FDA label). 2026. Read the source
6. DailyMed, US National Library of Medicine (Structured Product Label). Dicyclomine Hydrochloride - WARNINGS AND PRECAUTIONS, Peripheral and Central Nervous System (FDA label). 2026. Read the source
7. DailyMed, US National Library of Medicine (Structured Product Label). Dicyclomine Hydrochloride - USE IN SPECIFIC POPULATIONS, Nursing Mothers (FDA label). 2026. Read the source
8. DailyMed, US National Library of Medicine (Structured Product Label). Dicyclomine Hydrochloride Tablets and Capsules - DOSAGE AND ADMINISTRATION in Adults (FDA label). 2026. Read the source
9. DailyMed, US National Library of Medicine (Structured Product Label). Dicyclomine Hydrochloride - OVERDOSAGE (FDA label). 2026. Read the source
10. BMJ. Effect of fibre, antispasmodics, and peppermint oil in the treatment of irritable bowel syndrome: systematic review and meta-analysis (adverse events). 2008. PMID 19008265, DOI 10.1136/bmj.a2313. Read the source
11. DailyMed, US National Library of Medicine (Structured Product Label). Dicyclomine Hydrochloride Tablets and Capsules - ADVERSE REACTIONS, Clinical Trials Experience (FDA label, Lannett Company LLC). 2026. Read the source
12. DailyMed, US National Library of Medicine (Structured Product Label). Dicyclomine Hydrochloride - ADVERSE REACTIONS, Postmarketing Experience (FDA label). 2026. Read the source
13. DailyMed, US National Library of Medicine (Structured Product Label). Dicyclomine Hydrochloride Injection USP - WARNINGS AND PRECAUTIONS, Inadvertent Intravenous Administration (FDA label, Fosun Pharma USA Inc.). 2019. Read the source
14. DailyMed, US National Library of Medicine (Structured Product Label). Dicyclomine Hydrochloride - WARNINGS AND PRECAUTIONS, peripheral antimuscarinic effects (FDA label). 2026. Read the source
15. Cochrane Database of Systematic Reviews. Bulking agents, antispasmodics and antidepressants for the treatment of irritable bowel syndrome. 2011. PMID 21833945, DOI 10.1002/14651858.CD003460.pub3. Read the source
16. BMJ. Effect of fibre, antispasmodics, and peppermint oil in the treatment of irritable bowel syndrome: systematic review and meta-analysis (antispasmodic subgroups). 2008. PMID 19008265, DOI 10.1136/bmj.a2313. Read the source
17. The Lancet Gastroenterology & Hepatology. Efficacy of soluble fibre, antispasmodic drugs, and gut-brain neuromodulators in irritable bowel syndrome: a systematic review and network meta-analysis. 2020. PMID 31859183, DOI 10.1016/S2468-1253(19)30324-3. Read the source
18. Journal of Clinical Gastroenterology. Treatment of the irritable bowel syndrome with Bentyl (dicyclomine hydrochloride). 1981. PMID 7016973, DOI 10.1097/00004836-198106000-00009. Read the source
19. Cochrane Database of Systematic Reviews. Bulking agents, antispasmodics and antidepressants for the treatment of irritable bowel syndrome (authors’ conclusions). 2011. PMID 21833945, DOI 10.1002/14651858.CD003460.pub3. Read the source
20. BMJ. Effect of fibre, antispasmodics, and peppermint oil in the treatment of irritable bowel syndrome: systematic review and meta-analysis (included antispasmodic trials). 2008. PMID 19008265, DOI 10.1136/bmj.a2313. Read the source
21. The Lancet Gastroenterology & Hepatology. Efficacy of soluble fibre, antispasmodic drugs, and gut-brain neuromodulators in irritable bowel syndrome: a systematic review and network meta-analysis (interpretation). 2020. PMID 31859183, DOI 10.1016/S2468-1253(19)30324-3. Read the source
22. DailyMed, US National Library of Medicine (Structured Product Label). Dicyclomine Hydrochloride - CONTRAINDICATIONS (FDA label). 2026. Read the source
23. DailyMed, US National Library of Medicine (Structured Product Label). Dicyclomine Hydrochloride - CLINICAL PHARMACOLOGY, Pharmacokinetics (FDA label). 2026. Read the source