methantheline

Action and Spectrum

Actions and Spectrum: 

methantheline is an anticholinergic medication that exerts its effects by blocking the action of acetylcholine, a neurotransmitter in the nervous system. It primarily acts on muscarinic receptors, part of the autonomic nervous system.  

Action:  

methantheline belongs to a class of drugs called anticholinergics or parasympatholytics. Its primary action mechanism is to block acetylcholine binding to muscarinic receptors competitively. This inhibits the parasympathetic nervous system, leading to various effects on organs and systems controlled by cholinergic nerve pathways. 

Spectrum:  

methantheline’s effects are broad and systemic due to its influence on the parasympathetic nervous system. Some of the effects include: 

Smooth Muscle Relaxation: methantheline’s anticholinergic properties lead to the relaxation of smooth muscles, which can be beneficial in conditions where excessive smooth muscle contraction occurs, such as gastrointestinal spasms. 

Reduced Glandular Secretions: By blocking acetylcholine signaling, methantheline can decrease secretions from glands controlled by the parasympathetic nervous system. This includes reducing salivation, bronchial secretions, and gastric acid secretion. 

Cardiovascular Effects: methantheline can cause a mild increase in heart rate by reducing the influence of the parasympathetic nervous system on the heart. However, its effect is generally less pronounced than that of atropine, another commonly used anticholinergic. 

Central Nervous System Effects: While methantheline is not primarily known for its central effects, some anticholinergic medications can have mild sedative and cognitive effects due to their influence on cholinergic pathways in the brain. However, these effects are generally weaker than their peripheral actions. 

Urinary Effects: methantheline can relax the detrusor muscle of the bladder, which can help in bladder overactivity or spasms. 

Drug Interaction

Adverse Reaction

Frequency not defined 

Dry mouth 

Dizziness 

Blurred vision 

Constipation 

Drowsiness 

Difficulty urinating  

Black Box Warning

Black Box Warning: 

None 

Contraindication / Caution

Contraindication/Caution: 

Contraindication 

• Hypersensitivity or Allergy: Individuals with known hypersensitivity or allergy to methantheline or other anticholinergic medications should not use methantheline due to the risk of severe allergic reactions. 
• Narrow-Angle Glaucoma: methantheline can cause pupillary dilation and increase intraocular pressure, worsening the condition in individuals with narrow-angle glaucoma. It should be avoided in individuals with this type of glaucoma. 
• Gastrointestinal Obstruction: methantheline’s smooth muscle relaxant effects can potentially worsen conditions characterized by gastrointestinal obstruction, such as paralytic ileus. It is contraindicated in these situations. 
• Urinary Retention: methantheline’s relaxation of the detrusor muscle of the bladder can exacerbate urinary retention, especially in individuals with a history of urinary retention or benign prostatic hyperplasia (BPH). 
• Myasthenia Gravis: It is a neuromuscular disorder characterized by muscle weakness and fatigue. Anticholinergic medications like methantheline can worsen muscle weakness in individuals with this condition. 
• Severe Ulcerative Colitis: methantheline’s effects on smooth muscle relaxation can potentially worsen inflammation and complications in individuals with severe ulcerative colitis. 
• Severe Cardiac Conditions: methantheline’s effects on heart rate and rhythm could be problematic in individuals with severe cardiac conditions, such as arrhythmias or heart failure. 
• Obstructive Uropathy: methantheline can worsen conditions where urine flow is obstructed, such as in cases of obstructive uropathy or bladder neck obstruction. 
• Elderly Patients: While not a strict contraindication, caution should be exercised when using methantheline in elderly patients because of their increased susceptibility to the anticholinergic side effects of the medication. 
• Pregnancy and Breastfeeding: A healthcare provider should carefully evaluate the use of methantheline during pregnancy and breastfeeding, as the potential risks and benefits need to be considered. 

Caution 

• Elderly Patients: Elderly individuals are generally more susceptible to the anticholinergic side effects of medications like methantheline. This includes effects such as dry mouth, constipation, urinary retention, and confusion. Lower doses and close monitoring may be necessary in this population. 
• Pediatric Use: methantheline is not typically recommended for children because of limited safety and efficacy data in pediatric populations. 
• Underlying Medical Conditions: Individuals with certain medical conditions, such as cardiovascular diseases (e.g., heart arrhythmias), gastrointestinal disorders (e.g., gastroesophageal reflux disease), or urinary issues (e.g., urinary retention), require cautious use of methantheline. The medication’s effects on heart rate, smooth muscle relaxation, and urinary retention may exacerbate these conditions. 
• Prostatic Hypertrophy: Men with benign prostatic hyperplasia (BPH) or prostatic hypertrophy should use methantheline cautiously, as the medication’s anticholinergic effects can lead to urinary retention. 
• Closed-Angle Glaucoma: methantheline can lead to pupillary dilation and increased intraocular pressure, worsening closed-angle glaucoma. Individuals with this condition should avoid using methantheline. 
• Gastrointestinal Disorders: Patients with certain gastrointestinal disorders, such as gastrointestinal obstruction, paralytic ileus, or severe ulcerative colitis, should use methantheline cautiously due to its effects on smooth muscle relaxation. 
• Renal and Hepatic Impairment: Renal and hepatic impairment can affect methantheline’s metabolism and elimination. Dosing adjustments might be necessary for individuals with impaired kidney or liver function. 
• Pregnancy and Breastfeeding: A healthcare provider should carefully evaluate the use of methantheline during pregnancy and breastfeeding.  
• Central Nervous System Effects: methantheline’s anticholinergic properties can potentially lead to central nervous system effects such as drowsiness, dizziness, and confusion. Caution should be exercised when activities requiring mental alertness, such as driving, are undertaken while using this medication. 
• Drug Interactions: methantheline can interact with other medications, potentially enhancing or reducing their effects. Before using methantheline, it’s essential to inform your healthcare provider about all the drugs, supplements, and herbal products you are taking. 
• Individual Variability: Responses to anticholinergic medications can vary widely among individuals. Some people might experience more pronounced side effects or have heightened sensitivity to the medication. 

Pregnancy / Lactation

Pregnancy consideration:  

US FDA pregnancy category: Not assigned. 

Lactation:   

Excreted into human milk: Not known. 

Pregnancy category: 

• Category A: well-controlled and Satisfactory studies show no risk to the fetus in the first or later trimester. 
• Category B: there was no evidence of risk to the fetus in animal studies, and there were not enough studies on pregnant women. 
• Category C: there was evidence of risk of adverse effects in animal reproduction studies, and no adequate evidence in human studies must take care of potential risks in pregnant women.    
• Category D: adequate data with sufficient evidence of human fetal risk from various platforms, but despite the potential risk, and used only in emergency cases for potential benefits.    
• Category X: Drugs listed in this category outweigh the risks over benefits. Hence, these categories of drugs need to be avoided by pregnant women.    
• Category N: There is no data available for the drug under this category. 

Pharmacology

Pharmacology: 

methantheline, an anticholinergic medication, exerts its pharmacological effects by competitively blocking acetylcholine binding to muscarinic receptors in various tissues, inhibiting parasympathetic nerve activity. This generally results in the relaxation of smooth muscles in the gastrointestinal tract, urinary bladder, and other organs, leading to decreased secretions, reduced smooth muscle contractions, and dilation of pupils. Due to its systemic action, methantheline treats conditions such as peptic ulcers, gastrointestinal spasms, excessive salivation, and urinary urgency.  

Pharmacodynamics: 

Mechanism of action: methantheline exerts its pharmacological effects primarily through its anticholinergic activity. The primary mechanism of action of methantheline involves its interaction with muscarinic receptors, which are a type of receptor that responds to the neurotransmitter acetylcholine.  

• Antagonism of Muscarinic Receptors: methantheline is classified as an anticholinergic medication. It competitively binds to muscarinic receptors on various tissues and organs throughout the body. Muscarinic receptors are a subtype of acetylcholine receptors in the parasympathetic nervous system. 
• Inhibition of Acetylcholine Binding: By binding to muscarinic receptors, methantheline effectively prevents acetylcholine, the neurotransmitter released by parasympathetic nerves, from binding to and activating these receptors. 
• Blockade of Parasympathetic Effects: Acetylcholine, when it binds to muscarinic receptors, initiates various parasympathetic responses in the body, including smooth muscle contraction, increased glandular secretions, and other activities associated with the “rest and digest” response. By blocking the binding of acetylcholine, methantheline inhibits these parasympathetic effects. 
• Smooth Muscle Relaxation: One of the critical effects of methantheline’s muscarinic receptor blockade is the relaxation of smooth muscles in various organs, such as the gastrointestinal tract and urinary bladder. This relaxation leads to decreased muscle contractions and can be beneficial in conditions characterized by excessive smooth muscle activity or spasms. 
• Reduction in Secretions: methantheline’s anticholinergic action also reduces the secretion of various glands, including salivary glands, bronchial glands, and gastric glands. This effect decreases salivation, bronchial secretions, and gastric acid secretion. 
• Dilation of Pupils: methantheline’s blockade of muscarinic receptors also affects the pupils of the eyes. The pupils may dilate by inhibiting the normal pupillary constriction response mediated by the parasympathetic nervous system (mydriasis). 

Pharmacokinetics: 

Absorption 

methantheline is administered orally as tablets or capsules. After ingestion, it is absorbed through the gastrointestinal tract, mainly in the stomach and the small intestine. The rate and extent of absorption may vary among individuals and might be influenced by factors such as food intake and individual variations. 

Distribution 

Once absorbed, methantheline is distributed throughout the body via the bloodstream. It can cross the BBB (blood-brain barrier) and distribute into various tissues and organs. Its effects are primarily exerted by binding to muscarinic receptors in target tissues, such as smooth muscles and glands. 

Metabolism 

methantheline undergoes metabolism primarily in the liver. The exact metabolic pathways may involve processes like hydrolysis and conjugation. The metabolism of methantheline can result in the formation of metabolites, which are then eliminated from the body. 

Elimination and Excretion 

After metabolism, the metabolites of methantheline and any unchanged drug are excreted primarily through the renal (kidney) route. They are filtered by the kidneys and eliminated in the urine. Some portion of the drug and its metabolites might also be excreted in bile and subsequently eliminated in feces. 

Adminstartion

Administration: 

methantheline is typically administered as an oral medication.  

Dosage: The dosage of methantheline can vary based on the medical condition being treated, the patient’s age, weight, and overall health. It’s essential to adhere to the prescribed dosage strictly. 

Frequency: methantheline is taken multiple times daily to maintain its effects throughout the day. Your healthcare provider determines the dosing frequency, which should be followed as directed. 

Timing: methantheline is commonly taken before meals to help control excessive secretions and smooth muscle activity in the digestive system. The timing of doses about meals may vary, so follow your healthcare provider’s instructions. 

Tablets or Capsules: methantheline is available in tablet or capsule form. Swallow the tablet or capsule whole with water. 

Duration: The duration of methantheline treatment will depend on the underlying medical condition and how well you respond to the medication. It’s important to continue taking the medication as prescribed unless instructed otherwise by your healthcare provider. 

Special Instructions: 

If a dose is missed, taking it as soon as possible is generally recommended. However, if the next scheduled dose is missed, it should be skipped and the following dose should be taken at the appropriate time. It is key to avoid taking a double dose of the drug in order to compensate for the missed dose. 

Store the drug at room temperature, away from moisture and direct sunlight, unless otherwise specified on the packaging. 

Patient Information Leaflet

Patient information leaflet 

Generic Name: methantheline 

Why do we use methantheline? 

methantheline is an anticholinergic medication used to treat various medical conditions by blocking the action of acetylcholine on muscarinic receptors.  

Gastrointestinal Disorders: 

Peptic Ulcers: methantheline can help reduce stomach acid secretion and decrease gastric acid production, making it helpful in treating peptic ulcers. 

Gastrointestinal Spasms and Irritable Bowel Syndrome (IBS): 

methantheline’s smooth muscle relaxant properties can help alleviate gastrointestinal spasms and cramps, making it beneficial for conditions like irritable bowel syndrome (IBS). 

Excessive Salivation and Drooling: 

methantheline’s ability to reduce salivary gland secretions can help manage conditions that lead to excessive salivation and drooling. 

Excessive Sweating (Hyperhidrosis): 

methantheline’s anticholinergic effects can reduce sweat gland activity, making it helpful in managing excessive sweating, especially in localized areas. 

Control of Respiratory and Bronchial Secretions: 

methantheline can reduce excessive respiratory and bronchial secretions in chronic obstructive pulmonary disease and also cystic fibrosis conditions. 

Preoperative and Preanesthetic Medication: 

methantheline’s ability to reduce salivary and respiratory secretions can be helpful as a preoperative medication to minimize secretions during surgical procedures. 

Adjunctive Treatment for Parkinson’s Disease: 

methantheline can be used as an adjunctive treatment for Parkinson’s disease to help manage some of the involuntary movements and symptoms associated with the condition. 

Management of Urinary Incontinence: 

methantheline’s effects on the bladder’s detrusor muscle can help reduce overactivity and urinary urgency, making it helpful in managing specific urinary incontinence.