Bethanechol is a prescription medication classified as a cholinergic agent, specifically a parasympathomimetic. It stimulates functions controlled by the parasympathetic nervous system. Patients typically take bethanechol orally, often in tablet form. Its primary role involves promoting activity in specific smooth muscles.
Primary Medical Applications
Bethanechol is primarily prescribed to address urinary retention, a condition where the bladder cannot fully empty. The medication helps by stimulating the bladder muscle to contract more effectively, facilitating urination.
One significant application is in treating non-obstructive urinary retention that occurs after surgery, known as postoperative urinary retention. Surgical procedures can sometimes temporarily impair bladder function, and bethanechol helps restore normal voiding. Similarly, it is used for postpartum urinary retention, which can affect individuals after childbirth.
Bethanechol also plays a role in managing overflow incontinence caused by neurogenic bladder atony. This condition involves a weakened or underactive bladder muscle due to nerve damage, leading to incomplete emptying and leakage. Bethanechol helps patients with neurogenic bladder empty their bladders more completely. Mechanical obstructions must be ruled out before using bethanechol for these conditions.
How Bethanechol Works
Bethanechol functions as a direct-acting parasympathomimetic agent, mimicking the actions of the parasympathetic nervous system. Its mechanism involves selectively stimulating muscarinic receptors. It binds to postganglionic muscarinic receptors, particularly M3 receptors, which are abundant in the bladder and gastrointestinal tract.
This binding action effectively mimics acetylcholine, a natural neurotransmitter. Unlike acetylcholine, bethanechol is not readily broken down by cholinesterase enzymes, allowing its effects to be more prolonged. Stimulation of M3 receptors in the bladder leads to increased tone and contraction of the detrusor muscle, the main muscle responsible for expelling urine.
Beyond its effects on the bladder, bethanechol also acts on muscarinic receptors in the gastrointestinal tract. This can lead to increased gastric motility and tone, potentially restoring normal peristalsis, the wave-like muscle contractions that move food through the digestive system. The drug’s structure, which includes a charged quaternary amine, prevents it from crossing the blood-brain barrier, minimizing central nervous system side effects.
Important Considerations and Administration
When taking bethanechol, patients may experience certain side effects, including sweating, flushing, abdominal cramps, nausea, and diarrhea. Other possible effects are burping, increased saliva production, headache, dizziness, and a general feeling of being unwell. It is important to consult a healthcare provider if these reactions are severe or persistent.
Bethanechol has several contraindications. It should not be used in individuals with conditions such as asthma, peptic ulcers, or an overactive thyroid gland (hyperthyroidism). Patients with urinary or gastrointestinal obstruction, or those who have recently undergone intestinal or bladder surgery, should also avoid this medication. These contraindications are due to the drug’s action, which could exacerbate symptoms in such conditions.
For optimal absorption and to minimize nausea and vomiting, bethanechol tablets are taken orally on an empty stomach. This means administering the medication at least one hour before or two hours after a meal. The effects of an oral dose begin within 30 minutes, reaching maximum impact around 60 to 90 minutes, and last for about one hour. Bethanechol is a prescription medication and must always be used under the guidance and supervision of a medical professional.