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Medical Disclaimer: This information is for educational purposes only and is not a substitute for professional medical advice.
Other
Homatropine methylbromide is a quaternary ammonium antimuscarinic agent used primarily as an adjunct in gastrointestinal therapy and as a deterrent to overdose in combination cough medications. It functions by inhibiting parasympathetic nerve impulses to reduce spasms and secretions.
Name
Homatropine Methylbromide
Raw Name
HOMATROPINE METHYLBROMIDE
Category
Other
Drug Count
4
Variant Count
11
Last Verified
February 17, 2026
RxCUI
992668, 992656, 992660, 992671, 992675
UNII
68JRS2HC1C, NO70W886KK
About Homatropine Methylbromide
Homatropine methylbromide is a quaternary ammonium antimuscarinic agent used primarily as an adjunct in gastrointestinal therapy and as a deterrent to overdose in combination cough medications. It functions by inhibiting parasympathetic nerve impulses to reduce spasms and secretions.
Detailed information about Homatropine Methylbromide
This page is for informational purposes only and does not replace medical advice. Consult a qualified healthcare professional before using any medication containing Homatropine Methylbromide.
Homatropine methylbromide is a semi-synthetic quaternary ammonium derivative of the belladonna alkaloid atropine. It belongs to a pharmacological class known as antimuscarinics or anticholinergics. Historically, this medication was widely utilized as an adjunct in the treatment of peptic ulcers and various gastrointestinal disorders characterized by hypermotility (excessive movement) or spasms. However, in contemporary clinical practice, homatropine methylbromide is most frequently encountered as a secondary ingredient in combination antitussive (cough suppressant) medications, most notably paired with hydrocodone bitartrate.
FDA approval for homatropine methylbromide dates back several decades, reflecting its long-standing presence in the pharmacopeia. As a quaternary ammonium compound, it possesses a permanent positive charge, which significantly alters its pharmacological behavior compared to its tertiary amine counterpart, homatropine hydrobromide (which is primarily used in ophthalmic solutions). This chemical structure limits its ability to cross the blood-brain barrier, theoretically reducing central nervous system (CNS) side effects while focusing its activity on peripheral muscarinic receptors located in the gut, lungs, and secretory glands.
At the molecular level, homatropine methylbromide acts as a competitive antagonist at muscarinic acetylcholine receptors (M1 through M5). Acetylcholine is a primary neurotransmitter of the parasympathetic nervous system, responsible for the 'rest and digest' functions of the body. By binding to these receptors, homatropine methylbromide prevents acetylcholine from exerting its effects.
In the gastrointestinal tract, this blockade results in decreased gastric motility and a reduction in the secretion of gastric acid and other digestive enzymes. In the context of cough suppression, while the hydrocodone component acts on the brain's cough center, the homatropine methylbromide is included at sub-therapeutic doses to serve as a 'deterrent' to abuse. If a patient attempts to take an excessive amount of the combination syrup to achieve a high from the hydrocodone, the homatropine will cause unpleasant anticholinergic effects (such as severe dry mouth, blurred vision, and rapid heartbeat), thereby discouraging overdose. Additionally, it may provide some peripheral drying of respiratory secretions, which can be beneficial in certain types of coughs.
Understanding the pharmacokinetics of homatropine methylbromide is essential for grasping its clinical utility and safety profile.
The primary FDA-approved indications for homatropine methylbromide include:
Off-label uses are rare but may include the management of excessive salivation (sialorrhea) or as a mild antispasmodic for bladder issues, although more selective agents are typically preferred today.
Homatropine methylbromide is available in several formats, though availability varies by region:
> Important: Only your healthcare provider can determine if Homatropine Methylbromide is right for your specific condition. The use of this medication must be supervised by a professional who can monitor for anticholinergic toxicity.
For the treatment of gastrointestinal disorders such as peptic ulcers or hypermotility, the standard adult dosage of homatropine methylbromide is typically 5 mg to 10 mg taken three to four times daily. Healthcare providers usually recommend taking the dose approximately 30 to 60 minutes before meals and at bedtime to maximize the antispasmodic effect on the digestive tract.
When used in combination with hydrocodone for cough suppression, the dosage is determined by the hydrocodone content. A common adult dose is one tablet or 5 mL of syrup (containing 1.5 mg of homatropine methylbromide) every 4 to 6 hours. It is critical not to exceed the prescribed frequency, as the cumulative effect of the anticholinergic can lead to toxicity.
Homatropine methylbromide is not generally recommended for use in very young children due to their increased sensitivity to anticholinergic effects. For children aged 6 to 12 years, the dosage in combination cough products is typically half the adult dose (0.75 mg of homatropine) every 4 to 6 hours. Use in children under the age of 6 is often contraindicated or requires extreme caution and precise weight-based dosing by a specialist. Always consult a pediatrician before administering any product containing this ingredient to a child.
Patients with impaired kidney function may experience decreased clearance of homatropine methylbromide. While specific GFR-based (Glomerular Filtration Rate) guidelines are not universally established, healthcare providers typically initiate treatment at the lowest possible dose and monitor for signs of systemic accumulation, such as urinary retention or extreme dry mouth.
Caution is advised in patients with significant liver disease. Although the liver is not the sole route of elimination, impaired metabolism can potentially prolong the drug's half-life. Monitoring for increased side effects is the standard clinical approach.
Geriatric patients are highly susceptible to the side effects of anticholinergics. The 'Beers Criteria' for potentially inappropriate medication use in older adults often flags drugs like homatropine methylbromide. In this population, doses should be started low, and patients must be monitored for confusion, dizziness, and falls.
If you miss a dose, take it as soon as you remember. However, if it is almost time for your next scheduled dose, skip the missed dose and resume your regular schedule. Do not double the dose to catch up, as this significantly increases the risk of anticholinergic side effects or toxicity.
Signs of a homatropine methylbromide overdose include severe dry mouth, dilated pupils, blurred vision, hot and flushed skin, rapid heart rate (tachycardia), confusion, agitation, and inability to urinate. In severe cases, respiratory depression or coma can occur, especially if taken with narcotics. If an overdose is suspected, contact a poison control center or seek emergency medical attention immediately. Treatment usually involves gastric lavage and supportive care; in extreme cases, the antidote physostigmine may be administered by medical professionals.
> Important: Follow your healthcare provider's dosing instructions exactly. Do not adjust your dose or stop the medication without medical guidance, as this could lead to a return of symptoms or unexpected reactions.
Because homatropine methylbromide blocks the parasympathetic nervous system, 'drying' effects are very common. These are often dose-dependent and include:
> Warning: Stop taking Homatropine Methylbromide and call your doctor immediately if you experience any of these serious symptoms:
Prolonged use of homatropine methylbromide may lead to chronic constipation or chronic dry mouth, the latter of which can cause significant periodontal (gum) disease and tooth loss. There is also emerging clinical concern regarding the 'anticholinergic burden'—the cumulative effect of taking multiple anticholinergic drugs over many years. Some observational studies suggest a potential link between high long-term anticholinergic exposure and an increased risk of cognitive decline or dementia in older populations, though this has not been definitively proven for homatropine methylbromide specifically.
There are currently no standalone FDA black box warnings for homatropine methylbromide. However, when it is formulated in combination with hydrocodone, it carries the extensive Black Box Warnings for Opioids, which include risks of addiction, abuse, misuse, life-threatening respiratory depression, and neonatal opioid withdrawal syndrome. It also warns against the risks of concomitant use with benzodiazepines or other CNS depressants.
Report any unusual symptoms or persistent side effects to your healthcare provider to ensure your treatment remains safe and effective.
Homatropine methylbromide is a potent medication that requires careful monitoring. Patients must be aware that this drug can impair the body's ability to regulate temperature. Because it reduces sweating, you are at a significantly higher risk of heat exhaustion and heat stroke. Avoid strenuous exercise in hot weather and stay well-hydrated. Furthermore, because it can cause blurred vision and drowsiness, you should not drive or operate heavy machinery until you know how the medication affects you.
No FDA black box warnings exist for Homatropine Methylbromide as a single-entity agent. However, as noted previously, the combination products containing hydrocodone carry severe warnings regarding opioid risks. Patients should refer to the specific labeling of the combination product for full details on respiratory depression and addiction risks.
Your healthcare provider may perform the following checks during treatment:
This medication frequently causes blurred vision and may cause mild drowsiness. These effects can significantly impair your ability to react quickly or see clearly. Do not engage in hazardous activities like driving or operating industrial equipment until you are certain that your vision and alertness are normal.
Alcohol should be avoided or strictly limited. Alcohol can increase the sedative effects of the medication (especially in combination products) and may worsen the dizziness or lightheadedness caused by homatropine methylbromide. Furthermore, both alcohol and anticholinergics can contribute to dehydration.
While homatropine methylbromide itself does not typically cause a withdrawal syndrome, stopping it suddenly after long-term use for GI issues might cause a 'rebound' effect, where symptoms like stomach cramps or diarrhea return with greater intensity. If you are taking the combination product with hydrocodone, sudden discontinuation can lead to opioid withdrawal. Always follow a tapering schedule if recommended by your doctor.
> Important: Discuss all your medical conditions, especially any history of glaucoma, heart disease, or prostate problems, with your healthcare provider before starting Homatropine Methylbromide.
For each interaction, the primary management strategy is dose adjustment or choosing an alternative therapy. Always provide your doctor with a complete list of all medications, including over-the-counter drugs and herbal supplements.
> Important: Tell your doctor about ALL medications, supplements, and herbal products you are taking to prevent dangerous drug interactions.
Homatropine methylbromide must NEVER be used in the following circumstances:
These conditions require a careful risk-benefit analysis by a physician:
Patients who have demonstrated a hypersensitivity (allergy) to other belladonna alkaloids, such as atropine, hyoscyamine, or scopolamine, are at a high risk of having a cross-allergic reaction to homatropine methylbromide. Symptoms can range from mild rashes to life-threatening anaphylaxis.
> Important: Your healthcare provider will evaluate your complete medical history, including any history of eye disease or digestive blockages, before prescribing Homatropine Methylbromide.
Homatropine methylbromide is generally classified as FDA Pregnancy Category C. This means that animal reproduction studies have not been conducted, and there are no adequate and well-controlled studies in humans. It is unknown whether the drug can cause fetal harm or affect reproduction capacity. However, because it is an anticholinergic, there is a theoretical risk that it could affect the fetal heart rate or GI motility if it crosses the placenta. It should only be used during pregnancy if the potential benefit clearly outweighs the potential risk to the fetus. Use during the third trimester is particularly scrutinized due to the potential for neonatal effects.
It is not known whether homatropine methylbromide is excreted in human milk. However, many anticholinergic drugs do pass into breast milk in small amounts. A significant concern is that anticholinergics may suppress lactation (reduce milk production) by inhibiting the action of acetylcholine on the mammary glands. Additionally, infants are particularly sensitive to anticholinergic side effects, such as rapid heart rate and constipation. Breastfeeding while taking this medication is generally discouraged, and a consultation with a lactation specialist or pediatrician is required.
Safety and effectiveness in the pediatric population have not been established through rigorous clinical trials for all indications. In combination cough products, it is often used in children over 6, but with extreme caution. Children are at a much higher risk for 'anticholinergic psychosis' (confusion and hallucinations) and hyperthermia (dangerously high fever) from these drugs. Always use a precise measuring tool and never exceed the dose recommended by a pediatrician.
Elderly patients (65 and older) are at the highest risk for adverse effects. Age-related declines in kidney and liver function can lead to higher blood levels of the drug. More importantly, the aging brain is more sensitive to the blockade of acetylcholine, which can lead to acute confusion, agitation, or worsening of pre-existing dementia. The risk of falls is significantly increased due to blurred vision and dizziness. Clinical guidelines generally suggest avoiding this class of drugs in the elderly whenever possible.
Since the kidneys are a primary route for the excretion of homatropine methylbromide and its metabolites, patients with a GFR below 60 mL/min should be monitored closely. While specific dose-reduction tables are not available, clinicians often reduce the frequency of dosing to prevent systemic toxicity. It is not known if the drug is cleared by hemodialysis.
In patients with significant liver dysfunction (Child-Pugh Class B or C), the metabolism of the drug may be delayed. This could result in a longer duration of action and more pronounced side effects. Caution and lower starting doses are the standard of care in this population.
> Important: Special populations, particularly the elderly and pregnant women, require individualized medical assessment and frequent monitoring while taking this medication.
Homatropine methylbromide is a competitive inhibitor of the muscarinic acetylcholine receptors. It specifically targets the postganglionic parasympathetic receptors in smooth muscle, cardiac muscle, and exocrine glands. By competing with acetylcholine for these binding sites, it prevents the activation of the G-protein coupled receptor signaling cascade. In the GI tract, this prevents the increase in intracellular calcium that normally leads to muscle contraction, thereby inducing relaxation of the smooth muscle and reducing the secretion of fluids and enzymes.
The onset of action for oral homatropine methylbromide is typically within 30 to 60 minutes. The duration of effect lasts approximately 4 to 6 hours, which dictates the multiple-daily dosing schedule. Unlike atropine, the methylbromide salt is a quaternary ammonium compound, which means it is permanently charged. This charge makes it more 'peripheral' in its action, as it does not easily pass through lipid membranes like the blood-brain barrier, though at high doses, some CNS penetration can still occur.
| Parameter | Value |
|---|---|
| Bioavailability | Low (<20%, erratic) |
| Protein Binding | Minimal to Moderate |
| Half-life | 2 - 4 hours |
| Tmax | 1 - 2 hours |
| Metabolism | Partial Hepatic Hydrolysis |
| Excretion | Renal (Primary) |
Homatropine methylbromide is classified as a Synthetic Antispasmodic / Antimuscarinic. It is related to other belladonna-derived drugs like hyoscyamine and methscopolamine. Within the therapeutic area of gastroenterology, it is considered an 'anticholinergic antispasmodic,' while in respiratory medicine, it is viewed as an 'antitussive adjunct.'
Medications containing this ingredient
Common questions about Homatropine Methylbromide
Homatropine methylbromide is primarily used as an adjunct treatment for stomach ulcers and other gastrointestinal conditions like hypermotility or spasms. In modern medicine, it is most commonly found as an ingredient in combination cough syrups that contain hydrocodone. Its role in these cough syrups is partly to help dry up respiratory secretions and partly to serve as a deterrent to abuse. Because it causes unpleasant side effects if taken in large amounts, it helps prevent people from taking too much of the narcotic cough medicine. Your doctor will determine the specific reason for your prescription based on your symptoms.
The most frequent side effects are related to the drug's 'drying' effect on the body's systems. Patients very commonly report dry mouth, blurred vision, and constipation. You may also notice a decrease in sweating, which can make you feel overheated in warm weather. Some people experience a slightly faster heart rate or difficulty starting urination. These effects are usually dose-dependent, meaning they may become more noticeable if your dose is increased. Always report persistent or bothersome side effects to your healthcare provider.
It is strongly advised that you avoid or strictly limit alcohol consumption while taking this medication. Alcohol can significantly increase the dizziness and drowsiness that the drug may cause, especially if you are taking a version that also contains hydrocodone. Combining alcohol with anticholinergic drugs can also increase the risk of dehydration and heat-related illnesses. Furthermore, alcohol can irritate the stomach, potentially worsening the GI conditions that homatropine is meant to treat. Always consult your doctor about your alcohol intake before starting this therapy.
Homatropine methylbromide is classified as Pregnancy Category C, which means its safety has not been fully established in human studies. It should only be used during pregnancy if your doctor determines that the benefits to the mother outweigh the potential risks to the developing baby. There is a concern that anticholinergic drugs could potentially affect the fetal heart rate or other functions. If you are pregnant or planning to become pregnant, you must discuss alternative treatments with your healthcare provider. Your doctor will carefully monitor your health if this medication is deemed necessary.
For most patients, the effects of an oral dose of homatropine methylbromide begin within 30 to 60 minutes of ingestion. If you are taking it for gastrointestinal spasms, you may feel relief within this timeframe as the muscles in your gut begin to relax. When used in a cough syrup, the cough-suppressant effect of the combination usually peaks within 1 to 2 hours. The total duration of the drug's effect is typically between 4 and 6 hours. Because it wears off relatively quickly, it is often prescribed to be taken multiple times throughout the day.
If you have been taking homatropine methylbromide for a long period, you should not stop taking it suddenly without consulting your doctor. While it is not typically addictive on its own, stopping it abruptly can cause a 'rebound' of gastrointestinal symptoms, such as increased stomach acid or cramping. If you are taking the combination product that contains hydrocodone, stopping suddenly can lead to opioid withdrawal symptoms like anxiety, sweating, and muscle aches. Your healthcare provider will usually provide a schedule to gradually reduce your dose to ensure your body adjusts safely.
If you miss a dose, you should take it as soon as you remember. However, if it is almost time for your next scheduled dose, you should skip the missed dose and simply take the next one at the regular time. Never take two doses at once to make up for a missed one, as this can lead to an overdose and severe anticholinergic side effects like a racing heart or inability to urinate. Maintaining a consistent schedule is the best way to ensure the medication works effectively. If you frequently forget doses, consider using a pill reminder app or a weekly pill box.
Weight gain is not a commonly reported side effect of homatropine methylbromide. Unlike some other classes of medications, such as certain antidepressants or antipsychotics, anticholinergics do not typically interfere with metabolism or appetite in a way that leads to weight gain. However, the drug can cause significant constipation and fluid retention in some individuals, which might lead to a temporary feeling of bloating or a slight increase in scale weight. If you notice rapid or significant weight changes while taking this medication, you should discuss this with your doctor to rule out other underlying causes.
Homatropine methylbromide can interact with many other drugs, particularly those that also have anticholinergic properties like certain antihistamines, antidepressants, and anti-seizure medications. Taking these together can lead to a 'toxic' buildup of side effects, including severe confusion or heat stroke. It can also interfere with how your body absorbs other medications by slowing down the movement of your digestive tract. You must provide your doctor and pharmacist with a complete list of all prescriptions, over-the-counter medicines, and herbal supplements you are taking. This allows them to check for dangerous interactions before you start treatment.
Yes, homatropine methylbromide is available in generic form, both as a single-ingredient tablet and in combination with hydrocodone. Generic versions are required by the FDA to be bioequivalent to the brand-name versions, meaning they work the same way in the body. Choosing the generic version can often be a more cost-effective option for patients. However, the availability of the single-ingredient generic may be limited in some pharmacies, as it is used less frequently today than the combination cough products. Check with your pharmacist to see which versions are covered by your insurance plan.