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Homebreast cancerDicyclomine (Bentyl) vs. hyoscyamine (Levbid)

Dicyclomine (Bentyl) vs. hyoscyamine (Levbid)

Dicyclomine vs. hyoscyamine: What’s the difference?

  • Dicyclomine and hyoscyamine are anticholinergics used to treat irritable bowel syndrome (IBS). 
  • Hyoscyamine is also used to treat peptic ulcer disease, hypermotility of the lower urinary tract, and gastrointestinal disorders. 
  • A brand name for dicyclomine is Bentyl. 
  • Brand names for hyoscyamine include Levbid, Levsin, Nulev, and Anaspaz. 
  • Side effects of dicyclomine and hyoscyamine that are similar include dry mouth, blurred vision, confusion, constipation, difficulty urinating, changes in taste, headache, nervousness, drowsiness, weakness, dizziness, impotence, flushing, nausea, and vomiting, 
  • Side effects of dicyclomine that are different from hyoscyamine include agitation, increased heart rate, heart palpitations, seizures, difficulty swallowing, delirium, difficulty falling asleep (insomnia), rash, skin redness, fainting, bloating, and difficulty breathing. 
  • Side effects of hyoscyamine that are different from dicyclomine include dry eyes, impaired memory, excitement, decreased sweating, dilated pupils, fever, loss of coordination, stomach pain, itching, and allergic reactions. 

What is dicyclomine? What is hyoscyamine?

Dicyclomine is an anticholinergic used to treat irritable bowel syndrome (IBS). Anticholinergic drugs block the effects of acetylcholine, the chemical transmitter that nerves release in order to cause muscles to contract. They prevent contraction of muscles by blocking the acetylcholine receptors on the muscle cells. Anticholinergic drugs also have a direct relaxing effect on muscle. Dicyclomine is used to reduce contraction of the muscles in the intestines.

Hyoscyamine is an anticholinergic drug used for treating irritable bowel syndrome, peptic ulcer disease, hypermotility of the lower urinary tract, and gastrointestinal disorders. Anticholinergics work by blocking the action of the neurotransmitter acetylcholine in the brain and at nerves throughout the body. Anticholinergic drugs like hyoscyamine affect the function of many organs by preventing acetylcholine from binding to its receptors. Hyoscyamine decreases the activity of muscles in the intestine and lower urinary tract. It reduces the production of sweat, saliva, digestive juices, urine, and tears. It also reduces the production of bronchial secretions. 


What is irritable bowel syndrome or IBS?
See Answer

What are the side effects of dicyclomine and hyoscyamine?


Common side effects include: 

  • dry mouth (xerostomia), 
  • blurred vision, 
  • confusion, 
  • agitation, 
  • increased heart rate, 
  • heart palpitations, 
  • constipation, 
  • difficulty urinating, and 
  • seizures. 

Other important side effects include: 

  • changes in taste perception, 
  • difficulty swallowing, 
  • headache, nervousness, 
  • drowsiness, 
  • weakness, 
  • dizziness, 
  • impotence, 
  • flushing, 
  • delirium, 
  • difficulty falling asleep, 
  • nausea, 
  • vomiting, 
  • rash, 
  • erythema, 
  • fainting, 
  • bloating, and 
  • difficulty breathing. 


Side effects include: 

  • Xerostomia 
  • Dry eyes 
  • Urinary retention 
  • Constipation 
  • Confusion 
  • Impaired memory 
  • Excitement 
  • Nervousness 

Other side effects include: 

  • Decreased sweating (anhidrosis) 
  • Flushing 
  • Blurred vision 
  • Dilation of the pupil of the eye (mydriasis) 
  • Loss of taste 
  • Weakness 
  • Fever 
  • Impotence 
  • Nausea 
  • Vomiting 
  • Headache 
  • Dizziness 
  • Ataxia 
  • Drowsiness 
  • Stomach pain 
  • Itching 
  • Allergic reactions 
  • Possible serious side effects include: 
  • Palpitations 
  • Increased heart rate 
  • Heat stroke 
  • Hallucinations 
  • Increased ocular pressure 
  • Psychosis 

What is the dosage of dicyclomine vs. hyoscyamine?


  • The recommended starting oral dose of dicyclomine is 20 mg given 4 times daily. The dose can be increased to 40 mg 4 times daily.  
  • The recommended intramuscular injection is 10 to 20 mg 4 times daily.  
  • The intramuscular injection is only used for 1 to 2 days if a patient cannot take capsules or tablets. 


  • The recommended oral dose of immediate release tablet or drops for treating irritable bowel syndrome, gastrointestinal disorders, or peptic ulcer disease is 0.125 mg to 0.25 mg every 4 hours. 
  • The maximum dose is 1.5 mg daily. 
  • The dose of immediate release formulations for treating hypermotility disorder is 0.15 to 0.3 mg orally every 6 hours. 

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What drugs interact with dicyclomine and hyoscyamine?


Antiglaucoma Agents 

Anticholinergics antagonize the effects of antiglaucoma agents and may increase intraoccular pressure. Anticholinergic drugs in the presence of increased intraocular pressure may be hazardous when taken concurrently with agents such as corticosteroids. Use of Bentyl in patients with glaucoma is not recommended. 

Other Drugs with Anticholinergic Activity 

The following agents may increase certain actions or side effects of anticholinergic drugs including Bentyl: 

  • amantadine, 
  • antiarrhythmic agents of Class I (for example, quinidine), 
  • antihistamines, 
  • antipsychotic agents (for example, phenothiazines), 
  • benzodiazepines, 
  • MAO inhibitors, 
  • narcotic analgesics (for example, meperidine), 
  • nitrates and nitrites, 
  • sympathomimetic agents, 
  • tricyclic antidepressants, and 
  • other drugs having anticholinergic activity. 
Other Gastrointestinal Motility Drugs 

Interaction with other gastrointestinal motility drugs may antagonize the effects of drugs that alter gastrointestinal motility, such as metoclopramide. 

Effect of Antacids 

Because antacids may interfere with the absorption of anticholinergic agents including Bentyl, simultaneous use of these drugs should be avoided. 

Effect on Absorption of Other Drugs 

Anticholinergic agents may affect gastrointestinal absorption of various drugs by affecting on gastrointestinal motility, such as slowly dissolving dosage forms of digoxin; increased serum digoxin concentration may result. 

Effect on Gastric Acid Secretion 

The inhibiting effects of anticholinergic drugs on gastric hydrochloric acid secretion are antagonized by agents used to treat achlorhydria and those used to test gastric secretion. 


The risk of adverse effects increases when hyoscyamine is combined with other drugs that block the action of acetylcholine. Such drugs include antimuscarinics, amantadine, haloperidol, phenothiazines, monoamine oxidase (MAO) inhibitors, tricyclic antidepressants, or some antihistamines. 

Antacids may interfere with the absorption of extended-release hyoscyamine. 

Are dicyclomine and hyoscyamine safe to use while pregnant or breastfeeding?


There are no adequate studies of the effect of dicyclomine in pregnant women at recommended doses (80-160 mg/day). Observation of women who received dicyclomine (up to 40 mg/day) containing products during the first trimester of pregnancy did not reveal any increased risk of harm to the fetus. 

Dicyclomine is excreted into breast milk. Since there have been reports of apnea (cessation of breathing) when dicyclomine has been given to children, it should not be used by nursing mothers. 


It is not known whether hyoscyamine can cause fetal harm when administered to a pregnant woman or can affect reproduction capacity. It should only be given to pregnant women when it is clearly needed. 

Hyoscyamine is excreted in breast milk. 


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