Bethanechol Chloride for Dogs, Bethanechol chloride is most frequently used to improve the ability of the bladder to contract. We normally think of urinating as a voluntary activity, but in fact there is a great deal more to it. In order to urinate, the bladder’s detrusor muscle must contract (squeezing the bladder empty) while simultaneously the lower sphincter must relax. These two activities must be coordinated or you will end up with the bladder squeezing against a closed sphinter or a dilated sphincter allowing passive leakage. The voluntary part is simply the when and where.
Bethanechol chloride works to strengthen the detrusor muscle’s contraction. There are several situations where this might be desirable. After a long-term urinary tract obstruction, the detrusor muscles become over-stretched and their elasticity is lost. The urinary bladder becomes limp and unable to empty. Similarly, there are certain spinal diseases that can disrupt the coordination of the sphincter and detrusor muscles. The so-called “upper motor neuron” diseases create an increase in sphincter tone while “lower motor neuron” diseases create a flaccid sphincter and a flabby bladder. Any of these situations might benefit from strengthening the ability of the urinary bladder to contract.
It works via the biochemistry of nerve stimulation. As mentioned, it is mostly used for bladder function issues but it can also be used to improve esophageal motion and can increase the tone of the lower esophageal sphincter (where the esophagus meets the stomach in the upper abdomen). This effect is sometimes helpful when treating megaesphagus.
How this Medication Works
Bethanechol chloride works neurologically by stimulating what are called muscarinic cholinergic receptors in the autonomic nervous system. (Think of the autonomic system as the part of one’s nervous system concerned with automatic involuntary functions such as motion of the intestinal muscle layers, pupil constriction and dilation, and, as mentioned, coordination of bladder wall and sphincter muscles.) By stimulating muscarinic cholinergic nerve receptors, bethanechol chloride is able to provide a stronger contraction message to the muscles those receptors control. This means, for example, the urinary bladder contracts harder.
One has many muscarinic cholinergic receptors besides those in the bladder and these will also be stimulated by bethanechol chloride. Increased contraction and movement in the intestine and stomach is a side effect, which can lead to diarrhea. Excess salivation and tear production can occur. Increasing the bladder’s detrusor muscle tone leads to a tighter bladder, which means less urine storage capacity and more frequent need to urinate.
The most common side effects at normal doses are diarrhea, appetite loss, vomiting, and drooling. The other side effects listed above tend to involve overdosing. Atropine is considered an antidote.
Interactions with other Drugs
If the patient’s urinary tract is not obstructed but has excess tone, it is helpful to combine bethanechol with a medication to relax the lower sphincter and urethra: diazepam or phenoxybenzamine.
Concerns and Cautions
- Keep away from light and store at room temperature. Do not refrigerate.
- Given orally. This medication can be given with or without food; however, mild upset stomach side effects are reduced if given with food.
- If a dose is skipped by accident, do not double up on the next dose. Simply give the dose when it is remembered and time the next dose accordingly.
In patients with a urinary obstruction issue (bladder neck tumors, idiopathic cystitis with blockage or other actual blockage), therapy should include an additional medication to help relax the bladder sphincter.
Bethanechol should not be used when the integrity of the bladder is in question (such as after a bladder surgery, or if the bladder has ruptured). A strong bladder contraction could cause the urinary bladder to leak urine into the abdomen in either of these situations. Similarly, bethanechol should not be used if i the integrity of the GI tract is in question as leaking through the tear or through a healing incision is possible if the intestine or stomach contracts too strongly.
Patients with stomach ulcers may secrete more acid while on bethanechol and should not receive this medication.
Bethanechol is also considered contraindicated or should be used with caution in patients with hyperthyroidism, inflammatory bowel disease, epilepsy, asthma, low blood pressure, and certain heart rhythm disturbances.
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