Cholinergic Therapy

Cholinergic therapy uses medications that affect the parasympathetic nervous system, which is often nicknamed the "rest and digest" or "feed and breed" system of the autonomic nervous system. When activated, the parasympathetic nervous system promotes activities such as digestion, elimination, and sexual arousal, and it helps the body calm down after periods of stress or danger. Commonly used cholinergic medications include bethanechol, a direct-acting cholinergic agonist, and atropine, a cholinergic antagonist.

Now, bethanechol is referred to as a parasympathomimetic because it works by mimicking the parasympathetic neurotransmitter, acetylcholine. By stimulating the muscarinic receptors in the bladder, it stimulates the contraction of the bladder's detrusor muscle and relaxes the external urinary sphincter, promoting urination in non-obstructive urinary retention. By stimulating muscarinic receptors in the gastrointestinal tract, it promotes bowel motility.

In contrast, atropine is referred to as a parasympatholytic, because it binds to acetylcholine receptors, blocking its effects. This leads to inhibition of the parasympathetic nervous system which results in increased heart rate and cardiac output and other antimuscarinic effects. It's used to treat conditions like overactive bladder and bradycardia. It can also be used to promote pupillary dilation during eye exams and can be given preoperatively to reduce excessive respiratory secretions.

Alright, cholinergic medications have several side effects which are related to their actions on the parasympathetic nervous system. By promoting parasympathetic effects in the heart and lungs, bethanechol can cause hypotension, bradycardia, and bronchoconstriction. It also promotes exocrine gland activity, causing sweating and increased salivation. In addition, increased gastrointestinal activity can cause cramping and diarrhea. Other effects include blurred vision due to miosis, or pupillary constriction, as well as urinary urgency.

On the other hand, atropine inhibits parasympathetic effects, so in the heart, it can cause tachycardia and palpitations. It reduces secretions throughout the body, causing decreased salivation and dry mouth, thickening of bronchial secretions, as well as anhidrosis or decreased sweating, resulting in dry, flushed skin, and an increased temperature.

Gastrointestinal activity slows down, which causes nausea, abdominal distension, and constipation. Other effects include mydriasis, or pupillary dilation, resulting in blurred vision, photophobia, and increased intraocular pressure. Atropine can also cross the blood brain barrier, and could result in agitation, hallucinations, or paranoid behavior. Lastly, urinary retention may occur.

Now, contraindications for bethanechol include any situation where increased activity of the urinary or gastrointestinal tract could cause trauma, such as mechanical obstructions or recent surgery on the bladder or bowels. Some additional contraindications include bradycardia, hypotension, and respiratory diseases like asthma.

Atropine should not be given to patients with narrow angle glaucoma, since it could cause acute glaucoma; and it should not be given to patients with myasthenia gravis because it can lead to worsening muscle weakness. Atropine should be avoided in patients with obstructive urinary or intestinal disorders because it can worsen urinary and bowel retention. Additional contraindications include use in patients with myocardial ischemia, heart failure, or hypertension, as it may cause cardiac ischemia; and it should not be used in patients at risk for hyperthermia.

When caring for a patient prescribed a cholinergic medication, begin by obtaining a baseline assessment, including vital signs and lung sounds, and their cardiovascular, respiratory, genitourinary, and gastrointestinal function.

For patients taking bethanechol, monitor their intake and output, and check for adventitious breath sounds. Also be sure to have IV atropine readily available in the case of a cholinergic overdose. If your patient is prescribed atropine, provide comfort measures for dry mucous membranes, such as mouth swabs, artificial tears, and lip balm. When providing cholinergic therapy, monitor your patient closely for side effects and evaluate the effectiveness of treatment.

Finally, if your patient is discharged home on a cholinergic medication, focus your education on safe self-administration. Be sure they know why their medication is prescribed, how to take the medication, and the length of treatment. Instruct patients taking bethanechol to make position changes slowly to avoid dizziness, and to have bathroom facilities close by after taking their medication.

For patients taking atropine, be sure to advise them to stay well hydrated and include fiber-rich foods in their diet to avoid constipation. Also, emphasize the importance of limiting strenuous activities outdoors when the temperature is hot to avoid hyperthermia. Then, review common side effects of their prescribed medication, and ensure they understand when they should notify their health care provider.

Alright, as a quick recap... Cholinergic medications affect the parasympathetic nervous system. Bethanechol is a direct-acting cholinergic agonist that works by mimicking the actions of acetylcholine and is used to treat non-obstructive urinary retention. Atropine is a cholinergic antagonist that blocks the actions of acetylcholine. Some of its uses include treatment for conditions like overactive bladder and bradycardia. Side effects are related to actions on the parasympathetic nervous system. Nursing considerations for cholinergic therapy include establishing a baseline assessment, monitoring for side effects, evaluating the effectiveness of cholinergic therapy, and providing teaching for safe self-administration.