Acetylcholine - Function and Role in the Body. How certain medication affects Muscarinic receptors and causes dry eyes, dry mucous membranes, and other anticholinergic side effects
To understand what acetylcholine is, one must first comprehend what a Synapse is: A Synapse is a connection between two neurons or between a neuron and a target cell. However, the connection is not electrical; instead, it occurs chemically through neurotransmitters. The signaling process unfolds as an electrical signal reaches the presynaptic nerve cell. Various types of neurotransmitters are then released from it, which are received by receptors on the postsynaptic nerve cell. From here, the chemical signals are once again converted into electrical ones, leading to an electrical nerve impulse being sent to the relevant part of the body. One such crucial neurotransmitter is acetylcholine.c
Acetylcholine is a neurotransmitter released from postganglionic nerves. This neurotransmitter is found, among other places, in the synapses between nerves and muscles, and the body utilizes this neurotransmitter to chemically transmit nerve signals to other cells such as neurons, muscle cells, and glandular cells.
When it comes to muscles, it's acetylcholine that is responsible for ensuring that the nerve impulse reaches its destination so that the muscle can contract. An enzyme called acetylcholinesterase then rapidly breaks down the remaining acetylcholine in the synapse, allowing for a new signal to be sent to the muscle for further movement. Therefore, acetylcholine is essential for various functions, including our ability to move.
Acetylcholine is also present in the brain's cortex, where it helps maintain normal electrical activity and, consequently, wakefulness. Additionally, acetylcholine is the neurotransmitter responsible for allowing electrical signals to reach glands in the body, triggering the production of secretions. Examples of such glands include salivary glands and tear glands. Acetylcholine also influences the secretion of digestive enzymes. For instance, acetylcholine is the neurotransmitter that prompts the pancreas to produce bile, which is crucial for breaking down fats in food.
In short, it can be said that acetylcholine regulates all types of secretion in the body. This ranges from saliva, tears, nasal mucin, to secretions and enzymes in the intestines. Additionally, acetylcholine functions to contract the muscles in the intestinal wall, aiding in the breakdown of the food we eat and its gradual movement downward through the intestines. From the aforementioned points, one can thus conclude that acetylcholine plays an extensive and highly important role in the human body. Medications that affect the production of this neurotransmitter can therefore have significant impacts on the body.
Medications and their effects on the neurotransmitter acetylcholine.
Systems in the body where signals are transmitted by acetylcholine are referred to as cholinergic. This is important to know because there are various types of medications that have so-called anti-cholinergic effects. Anti-cholinergic effects mean that the medication blocks the function of acetylcholine. When this effect is blocked, nerve signals do not reach the body parts that normally receive signaling via the neurotransmitter. In concrete terms, this means that tear glands, sweat glands, and salivary glands, for example, do not receive the signal to produce secretions. The switch for these body parts is effectively turned off. However, the impact doesn't only extend to the mentioned organs. All bodily functions that involve larger or smaller glands are affected. This includes the lungs, intestinal lining, reproductive organs, nasal lining, throat, mouth, and so on.
Deepening the understanding of the function of the neurotransmitter acetylcholine:
To delve a bit deeper into how acetylcholine functions, it's worth mentioning that acetylcholine activates muscarinic and nicotinic receptors in the body. Concerning muscarinic receptors, there are five types: M1, M2, M3, M4, and M5. Below is a general explanation of where these different types of receptors are located and how they impact the body. The information below is primarily sourced from the study titled "Muscarinic receptors: their distribution and function in body systems, and the implications for treating overactive bladder."
You can access the study at the following link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1751864/
Muscarinic acetylcholine receptor M1:
This receptor is commonly found in the central nervous system and in exocrine glands. Exocrine glands are those that secrete substances through channels to the body's mucous membranes. Examples of such glands include sweat glands, tear glands, salivary glands, the prostate gland, mucous glands in the respiratory tract, the exocrine part of the pancreas, mammary glands, glands in the ear canal, sebaceous glands (found in the skin), and more.
Speaking of sebaceous glands, these are found in various parts of the body in slightly different forms and with different functions. In English, they're referred to as "Sebaceous glands." The Meibomian glands in the eyelids are one type of sebaceous gland. Other examples of similar sebaceous glands in the body are located in the nose, specifically in the outer part of the nasal cavity, on the male genitalia (particularly on the glans penis), in the female genitalia (such as the labia minora and nipples), and more.
Muscarinic M1 receptors are also present in the brain, specifically in the hippocampus, cerebral cortex, and peripheral ganglia. Muscarinic M1 receptors also influence involuntary bodily functions, memory, and learning.
Muscarinic acetylcholine receptor M2:
These receptors are located in the heart and lungs, where they are responsible for slowing down the heart rate. Inhibiting the M2 receptor with anticholinergic medications like Atropine increases heart rate. The receptor is also found in the smooth muscle throughout the body, which covers many of the body's tubular cavities such as blood vessels, internal organs, intestines, esophagus, trachea, and the sphincter muscles. M2 receptors are also present in the dermis, close to hair follicles.
Muscarinic acetylcholine receptor M3:
The M3 receptor is found in various locations in the body, including the smooth muscles (as described above). Activation of this receptor typically leads to an increase in intracellular calcium and consequently a cholinergically-induced contraction in smooth muscle. This receptor is involved in processes such as intestinal motility (intestinal movement), where the smooth muscles around the intestines contract to facilitate digestion, cleansing, and emptying of the bowels. It's also involved in the contraction of the bladder during urination and the constriction of bronchi in the lungs.
Muscarinic acetylcholine receptor M4:
The M4 receptor is also present in the lungs and the central nervous system. Activation of the M4 receptor inhibits the release of acetylcholine in the striatum. The striatum is a region in the brain present in both hemispheres, affecting our cognition. It controls reward perception, future reward anticipation, decision-making, action planning, reinforcement, and motivation. The dorsal (upper) striatum controls impulsivity and inhibition of such impulses. In humans, the striatum activates in response to rewards or unexpected/intense stimuli. Dysfunction in the striatum can lead to conditions like depression and obsessive-compulsive disorder. Due to its involvement in reward perception, the striatum is also related to addiction. It's known to contribute to the reinforcing effects of stimulants, such as alcohol, through dopaminergic stimulation.
Muscarinic acetylcholine receptor M5:
The M5 receptor is present in many organs, but comprehensive explanations and research are lacking. Some known aspects include the fact that acetylcholine binding to the M5 receptor triggers several cellular responses, such as adenylate cyclase inhibition, phosphoinositide breakdown, and potassium channel modulation.
Muscarinic receptors in the body, localization, and function:
Muscarinic receptors are found throughout the body. Below are therefore just a few examples of where to find the receptors and what functions they have in the various tissues.
Bladder: All 5 Muscarinic receptors are found here, but M2 and M3 have been shown to be dominant. Both receptors have the function of contracting the bladder during urination.
Salivary glands: M1 and M3 receptors. Activation of both receptors leads to secretion of saliva.
Intestines: In studies of guinea pigs, M1-M5 have been found in the smooth muscle of the intestine. As far as humans are concerned, M2 and M3 are considered to be the receptors with the most functionality. However, M2 receptors are the receptors of which there are the most in number. In studies on dogs, it has been shown that the M3 receptor is the one most responsible for bowel movements through the activation of smooth muscle.
The brain: All 5 receptors are found here. Muscarinic receptors in the brain activate a variety of signaling pathways important for modulation of neuronal excitability, synaptic plasticity and feedback regulation by Acetylcholine.
The eyes: M1-M5 are found here, i.e. all Muscarinic receptors. The percentage distribution of each receptor type is as follows: M3 60-75%, M2 5-10%, M4-10%, M1 7%. In the Iris Sphincter (pupil muscle) 5%.
In studies on mice, it has been found that the M3 receptor contracts a smooth muscle in the eye called the "Iris Sphincter muscle" in English. This musculature is part of the Iris (I.E. the colored area that surrounds the pupil). The muscle's function is to contract the pupil to regulate the amount of light entering the eye.
In studies on rabbits, it has also been found that the M5 receptor works by contracting the so-called "Ciliary muscle" of the eye. DVS in the ring-shaped muscle of the eye which is responsible for accommodation. A process that occurs when the eye focuses on an object. (During accommodation, the lens either flattens or becomes concave). Further studies have also established that further influence on the pupil's ability to contract or dilate occurs through influence on the M2 receptor.
As for the M1 receptor, this is present in the Iris, Sclera (the white area around the iris) and in the epithelial cells that lie in front of the lens, i.e. between the lens capsule and the lens fibers. These epithelial cells are responsible for homeostasis of the lens. Homeostasis means that the body arranges the perfect conditions for optimal functioning of the organ. For example, the right fluid balance, the right temperature, the right PH, the right concentrations of blood sugar, mineral balance, etc.
Animal studies have also established that M1, M2 and M3 receptors can activate goblet cells (cells that produce secretions) on the conjunctiva (the conjunctiva of the eye). That is, the epithelial membrane that covers the inside of the eyelids and the membrane that covers the white part of the eye. The goblet cells on this membrane produce the secretion that is a significant part of the tear film.
Anticholinergics thus have many negative effects on the eye and from the text above you can now understand why a direct effect of Anticholinergics is light sensitivity and difficulty focusing the gaze as well as problems with dryness and blurred vision. From earlier in the text, we have also established that anticholinergics also shut down sebum production in the skin's sebaceous glands. The meibomian glands in the eyelids that produce fat for a stable tear film are to be considered a specialized sebaceous gland. Therefore, Anticholinergics also negatively affect this part of the tear film.
The Lacrimal Gland: At the time of writing, I have not been able to find any documents showing which Muscarinic receptors are found in the Lacrimal Gland. However, it has been found that the secretion of tears has increased if the Muscarinic receptor (M3) has been stimulated via the intake of a Muscarinic Agonist.
Source: Muscarinic receptor agonists and antagonists: effects on ocular
The heart: Muscarinic receptors M1, M3, M5 have been identified in the human heart. In animal studies, activation of certain Muscarinic receptors has been found to affect heart rate.
The nose: Muscarinic receptors are also found in the mucous membrane of the nose. These receptors play an important role in regulating vasoconstriction and vasodilation of the blood vessels in the nose (the ability of the blood vessels to increase or decrease in diameter). They thus control the function by allowing the turbinates (nasal breathing organs) to swell or contract as needed. In a research study (1.2) carried out on rabbits, it has been established that the secretion of Acetylcholine leads to vasodilatation, i.e. the diameter of the blood vessels increases and the mucous membrane of the nose swells, whereby the passage of air decreases.
Research study (1.2): M1 and M3 muscarinic receptors mediate relaxation and contraction in canine nasal veins: https://pubmed.ncbi.nlm.nih.gov/21679501/
In addition, the Muscarinic receptors also control the secretion-producing goblet cells in the mucosa. An activation of the Muscarinic receptors in the mucous membrane takes place through the signaling substance Acetylcholine and the consequence of this leads to a Parasympathetic reaction in the nervous system where goblet cells (small glands) in the mucous membrane are triggered to secrete secretions.
In study (1.1) "Muscarinic receptor subtypes in human nasal mucosa: characterization, autoradiographic localization, and function in vitro" they looked at the function of Muscarinic receptors M1, M2 and M3 in the nasal mucosa. Here it was concluded that receptor M1 and M2 coexisted in submucous glands (small glands inside the mucous membrane). It was also concluded that M1 receptors can control glandular secretion, while M3 receptors can regulate both secretion from glands and the control of blood vessel diameter in the nasal mucosa.
Research study (1.1): https://pubmed.ncbi.nlm.nih.gov/8427708/
Below you can see an in-depth lecture on Muscarinic receptors.
Antagonist and Agonist explanation
To understand which medications affect the effect of Acetylcholine and subsequently the Muscarinic receptors, you need to know what an Antagonist and an Agonist are.
An Agonist is a substance or medicine that binds to a receptor in a Synapse and stimulates activity in the Synapse. As an example, the following can be mentioned: An Agonist that attaches to a receptor that leads to a muscle thus causes the muscle to contract. An Agonist thus promotes bodily function.
An Antagonist, on the other hand, is a substance or drug that binds to the receptor in a Synapse and which then counteracts the action of the Synapse. That is, an antagonist can reduce or block the signal that would normally have been sent out from the Synapse. When the receptor is blocked, it can no longer perform its function. Body function is inhibited or completely shut down. Below you can see an in-depth film about antagonism and Agonism.
Muscarinic antagonist and anti cholinergic effect
A Muscarinic antagonist is thus a substance or medicine that binds to the Muscarinic receptor but counteracts these natural functions. The nerve signaling out of the synapse is thus weakened or blocked completely and thus the body's natural effect of Acetylcholine is blocked or reduced. The body function that would normally take place if nerve impulses were sent out from the Synapse will thus be affected by being completely absent or by being weakened. Medicines that are muscarinic antagonists are also referred to as anti cholinergic. Such a medicine has what is called an anti-cholinergic effect. That is, the medicine affects the Cholinergic system in the body negatively. Signaling is inhibited or blocked completely.
Anticholinergics a summary
So if you take medicines with an anti-cholinergic effect, all the functions that the Muscarinic receptors M1-M5 normally activate are affected. If you have read the text above, you now realize that there is an extensive negative impact on the body where many body signals are stopped or hindered that would normally be sent to various glands, tissues and organs. One of the most extensive effects this type of medicine has is that it affects all the body's glands. That is, the anticholinergic effect blocks the effect of Acetylcholine. The substance prevents the Muscarinic receptor from sending nerve impulses to the body's glands to produce secretions. This causes mucous membranes to dry out. If you take such a medication for a long time, the consequences can be great and many times irreversible. There are many who have had permanent problems with dry eyes after taking, for example, Antihistamines that have a strong anti-cholinergic effect for longer periods.
Now that you know this, you need to check if the medication you are taking has an anti-cholinergic effect. To do so, you may need to know what to search for. Here are some common names:
Anti cholinergic medication / Cholinergic blockers / Cholinergic antagonists / Muscarinic antagonists / Medications that have cholinergic effects / Medications that affect the cholinergic system / Parasympatholytics
Side effects of Anticholinergics - A list
NOTE: Below is not a complete list of side effects of Anticholinergics
Skin: Drier skin as the production of sebum in the sebaceous glands is inhibited. Reduced sweating with possible heatstroke as a result
Lungs: Impaired secretion in the bronchial mucosa, i.e. in the lungs. Increases risk of throat lung infection caused by breeze on antimicrobial effect of saliva and secretions
Eyes: When taking Anticholinergics - Accommodation difficulties (difficulty focusing the gaze). When taking Anticholinergics - Impaired vision caused by inhibitory effect on the tear film
When taking Anticholinergics - Increased pressure in the eye. This occurs because the muscle that releases the pressure in the eye is deactivated when acetylcholine is blocked. High pressure in the eye can over time cause Keratoconus and Glaucoma. Two conditions that impair vision. PS: High pressure in the eye is treated with the drug Pilocarpine, which is a Cholinergic Agonist and thus activates this muscle.
The three layers of the tear film are inhibited, ie less amount of Tears, Mucin and lipids. Long lasting Blepharitis and dysfunction of the meibomian glands in the eyelids. Finally, cell death of the meibomian glands with chronic dry eyes as a result. In the long run, erosions on the cornea (ulcers) that cause permanent poor vision (Astigmatism).
This is caused by chronic dryness where the cornea is damaged. NOTE This type of vision defect may be impossible or very difficult to correct with glasses. People who have suffered from dry eyes for years are also seen to a greater extent than other individuals to have developed Keratoconus. A conical shape change of the eye that causes impaired vision and increased dryness.
In the long run, inhibiting and lasting negative effect on all glands of the eye = Chronic dry eyes.
In the long run, the Meibomian glands in the eyelids can form back or have impaired function. The same thing can happen with the lacrimal gland and or with all the small goblet cells that sit on the eye and in the mucous membrane around the eye.
Dilation of the pupils (Mydriasis) with consequences see below:
Light sensitivity, Eye pain, blurred vision, headache. Glaucoma in predisposed patients
If you want to read about drugs that cause "dry eye disease" (chronic dry eyes), I would like to refer you to a good page here: 5 Worst Drugs that Cause Dry Eye Disease
Below you can also listen to a good lecture about the cause of dry eyes beyond Drug causes.
Mouth:
Dry mouth with bad breath
Long-term tooth decay as a result of dry mouth
Cognitive ability
Cognitive impairment (drowsiness, brain fog, lack of energy)
Impaired ability to concentrate
Mild confusion (especially in the elderly)
Hallucinations (visual or auditory)
Bladder
Urine retention (difficulty emptying the bladder), this when smooth muscle in the walls of the bladder is negatively affected
Incontinence (difficulty holding in urine)
Intestine and Stomach
Decreased intestinal peristalsis (bowel movements)
Constipation or change in stool consistency
Changes in stool consistency
In the long term, the gut is negatively affected in several different ways. The first way anticholinergics affect is that it inhibits the activity of smooth muscle. Such musculature is found in several different places in the body, the intestinal wall being one such place. This inhibits the intestine's ability to move food back and forth to break it down (break it down). A possible consequence of this is nutritional deficiency. Another consequence is constipation. The intestine must clean itself between meals and push the food on to the large intestine. This allows the gut to rest and recover. If this function is inhibited or blocked, it can lead to an overgrowth of pathogenic (bad) bacteria that irritates and irritates the mucous membrane. In addition, anticholinergics work in the same way in the gut as they do in the body's other glands. It lowers the production of secretions. A secretion that partly contains enzymes but also has an important function of creating a protective membrane in the intestine.
If you take anticholinergics for a long time, you get less secretions in the intestine. This together with a possible overgrowth of pathogenic bacteria affects the intestinal mucosa negatively with irritation and possibly low-grade inflammation. If, on top of this, you already have an intestinal disease such as Ulcerative Colitis and or Crohn's disease, this can contribute to triggering a relapse. In addition, anticholinergics can worsen or give rise to increased intestinal permeability in the long term. This is because the protective layer of secretions is missing at the same time as there are pathogenic bacteria that irritate the mucous membrane. A continuous increase in intestinal permeability over a long period of time is very negative for health and leads to the development of food intolerances. It also leads to an excessive activation of the immune system which is largely localized to the inside of the intestine. To read more about this refer to searching yourself on: Intestinal permeability or leaky gut.
Inhibition of muscle contraction in smooth muscleSmooth muscle is muscle tissue that is controlled by the autonomic nervous system (the involuntary nervous system). This muscle tissue sits in the walls of the body's many tubular cavities. Some examples are in: Intestines, bladder, blood vessels, esophagus, trachea and sphincter. Another place that also has smooth muscle is the area closest to the body's hair follicles. When you take anticholinergics, you completely inhibit or block nerve signals to smooth muscle. Since we have so many organs that contain this, it can have negative consequences for each individual organ. To take an example, it can be mentioned that Anticholinergics cause problems with urination if the signal to be sent to the smooth muscle of the bladder is inhibited or blocked. The bladder then has difficulty contracting and emptying may be difficult or impossible to complete fully.
source: The problems of anticholinergic adverse effects in older patients
NOTE: In 2011-2012 I worked at an HVB home for addicts. Here we had a younger guy between 23-26 years old. The person in question had stopped taking drugs but was now taking Atarax at a high dose (sedating and sleep-inducing medication with a strong anti-cholinergic effect). As previously described, a common anticholinergic effect is that nerve signals to smooth muscle in the bladder are inhibited. Despite his young age, he had to use a catheter to empty his bladder. Thus anti cholinergic medicine can have such a strong effect even on younger individuals.
GenerallyDryness problems from all the body's mucous membranes
Dryness problems in the vagina in both men and women
Dry nose and increased risk of infection due to lack of protective secretions
So now we have a relatively good picture of how anticholinergic medicine affects the body. But why do we need to know this? Yes, my experience is that few pharmaceutical companies write out all the side effects that are related to Anti Cholinergic influence. Hence, we ourselves need to have background knowledge to be able to determine whether a medicine we take or intend to take will have an anti-cholinergic effect. Many problems today such as dry eyes, dry mouth and generally dry mucous membranes are today considered to be age-related. The question is, however, is this really the whole truth? Or could it be that older people are given medications that have an anti-cholinergic effect and at the same time are more sensitive to this than younger people? Yes, in any case, they like to hide a complete list of side effects in FASS on all the anti-cholinergic effects a medicine could have. In the best case, it might be written that the medication has an anti-cholinergic effect, but most laymen lack the knowledge to understand what this means. In addition, my own experience is that many doctors lack knowledge about anticholinergic effects and which medications have such effects. Personally, I have applied to the Eye clinic at the local hospital somewhere 7-10 times. On each occasion I have asked if the medication I am taking could be the cause of my dry eyes? Never once have I received an answer that this is the case. This is believed to be that current medicine (antihistamine) and Zolpidem have strong anticholinergic effects.
What are anticholinergics used for?
Here are some examples:
(1) Overactive bladder, i.e. if you have to urinate frequently. Here, the drug works by blocking the nerve signal to the bladder.
(2) In diarrhoea, here too the signal to smooth muscle is blocked, in this case the muscle that pushes the food forward in the intestine. Such a blocked signal leads to a slower intestinal passage and should thus be able to counteract diarrhea as the colon gets more time to reabsorb the liquid.
(3) In Parkinson's. In this disease, you have, among other things, involuntary muscle movements, and as you probably remember, acetylcholine is the signal substance that causes the muscles to contract. With the help of an anticholinergic drug, this signal can thus be blocked.
(4) Excessive sweating, here the signaling to sweat glands is blocked.
(5) In Asthma. In this condition, you get an excessive contraction of smooth muscle in the Bronchi (in the lungs). Anticholinergics thus also block the signal to the muscle here. The result is that the muscle relaxes and the person in question then gets better oxygenation and breathing.
(6) Sleep problems. In many cases, sleep problems are due to a brain that cannot stop thinking. Such a brain has a high level of nerve signaling between the different areas of the brain and the person in question does not descend into dominance by the Para sympathetic nervous system. Because Acetylcholine is a neurotransmitter that allows Neurons to send nerve signals, the neurotransmitter acts activatingly in the brain. If you then use anticholinergic sleep medication such as Atarax, Propavan, Zolpidem, Lergigan, Oxascand, etc., the effect of Acetylcholine in the brain is blocked. The signaling thus goes down, the thoughts slow down and the person in question becomes tired.
(7) Worry and anxiety. The reason that anticholinergics are used for these conditions is, as described above for sleep disorders, that it reduces nerve signaling in the brain. This calms the flow of thought and gives rise to a more relaxed state.
(8) Allergies. In case of allergy to, for example, grass and pollen etc., the immune system overreacts against substances that are actually harmless. During this reaction, Histamine is secreted, a substance that leads to swelling and increased secretion from mucous membranes. This can mean, for example, that the nose and eyes run. By giving antihistamine, you block histamine receptors and thus turn off nerve signals to mucous membranes to produce more secretions. Here you also need to know that Histamine and Acetylcholine are two bioactive substances that are similar. In amino acid sequencing of the Histamine 1 receptor, it has been found that this is more than 30% similar to the Muscarinic Acetylcholine receptor. Therefore, antihistamines also have an anticholinergic effect.
Study: Editorial Anticholinergic activity of antihistamines
Quote from study: “Histamine and acetylcholine are similar bioactive substances. In fact, the synergic action of histaminergic neurons and acetyl-choline neurons elevates alertness levels and promotes cognitive function (Blandina et al., 2004). The amino acid sequence (primary structure) of H1 receptors shows greatest similarity to that of a muscarinic acetylcholine receptor, and the two show a homology of 30% or more. Therefore, classical first-generation antihistamines, such as promethazine, have an anticholinergic activity. This anticholinergic activity induces symptoms such as drymouth, visual disturbances (mydriasis, photophobia, and diplo-pia), tachycardia, urinary retention, constipation, agitation, and confusion (high-dose administration).
(9) Motion sickness is a condition that is also treated with anticholinergics. Effect occurs when nerve signals to the balance center are inhibited.
Final words to the paragraph: When it comes to the medical use of anticholinergic drugs, it can also be good to know that certain conditions are treated directly by the anticholinergic effect of the medication. For example, certain anticholinergic medication is used against excessive urination to block the nerve signal to the bladder. In other cases, you use medications that have a different goal and a different effect on the body, but where you instead get a cholinergic effect as a side effect. This of course means that you cannot Google your way to the medicine that has an anticholinergic effect by searching for "What are anticholinergics used for".
Drug list Anticholinergics
Unfortunately, I have not managed to find a complete list of all drugs with anticholinergic effects. The list below, presented in English, is thus far from comprehensive. The Anticholinergic group is considerably larger than this list shows. Therefore, I instead urge you to seek more information about the particular medicine you are wondering about. For example, you can google: "anticholinergic effects of antihistamines" or, for example, "anticholinergic effects of Propiomazine" and so on.
In general, it can be said that most drugs that in one way or another have a dampening effect on the Autonomic Nervous System have an anti-cholinergic effect. That is, sleeping pills, sedatives, antipsychotics and antidepressants. Some other common groups are also Incontinence medicines and Antihistamines. Note that Antihistamines are a group of drugs that are used both for allergies, sleep problems and anxiety. They have an anticholinergic effect and in addition they also have another mode of action which means that they affect the Histamine receptors in the body. This makes them EXTREMELY drying and is therefore one of the most drying preparations available today. There are many people who have had their eyes chronically dry after a period of using these types of medications. In fact, many antihistamines are used precisely to inhibit mucus formation in various conditions. Hence, the medicine is purely designed to dry out mucous membranes.
Also note that long-term use of, for example, antihistamines can cause permanent functional impairment in mucous membranes even after the medication has been stopped. There are therefore good reasons to stay away from these types of medications and from other medications with anticholinergic effects.
NOTE The list below may be the name of the medication or in some cases the name of the active substance in the medication. Also note that the names are the English ones, the Swedish names may differ partially or completely.
You can also check the Okloka list. This is a list of medicines that should not be given to the elderly as they have a high risk of side effects. This often means that older people are even more negatively affected by medications with a large anticholinergic effect than younger people are. Hence, many of the medicines found on this list are anticholinergic medicines. Before we continue with my own compiled list of anticholinergics, it should also be mentioned that there are drugs that are a Muscarinic Agonist. That is, drugs that, unlike Muscarinic Antagonists, strengthen the signaling to the body's cholinergic system. These agents can thus strengthen the body's ability to, for example, produce secretions from the body's glands, so they have the opposite effect to Anticholinergics.
Here are examples of medicines with Muscarinic Agonism
TYRVAYA: (also known by the name: OC-01). This is an FDA approved Medicine in the form of a nasal spray that will be launched in November 2021. Oyster Point Pharma is the company behind this medicine. The drug requires a prescription and at the time of writing is not available in Europe.
"TYRVAYA, formerly known as OC-01, is believed to bind to cholinergic receptors in the nose to help activate the parasympathetic nervous system, thus increasing basal tear production to improve the signs and symptoms of dry eye disease. This medication provides a new and convenient way to administer dry eye treatment without further irritating the ocular surface"
Bethanechol: A muscarinic agonist used to treat postoperative and postpartum nonobstructive functional urinary retention and neurogenic atony of the bladder with retention.
Cevimeline: A muscarinic agonist with parasympathomimetic activities that is used for the symptomatic treatment of dry mouth in patients with Sjögren's Syndrome.
Pilocarpine: A muscarinic cholinergic agonist used on the eye to treat elevated intraocular pressure, various types of glaucoma, and to induce miosis. Also available orally to treat symptoms of dry mouth associated with Sjogren's syndrome and radiotherapy.
NGX267: Investigated for use/treatment in alzheimer's disease and schizophrenia and schizoaffective disorders.
Methacholine: A parasympathomimetic bronchoconstrictor used to diagnose bronchial hyperreactivity in subjects who do not have clinically apparent asthma.
Dietary supplement to increase the production of Acetylcholine
There are no dietary supplements that directly add Acetylcholine to the body. However, there are Choline supplements which are a precursor to Acetylcholine that the body itself can use to produce Acetylcholine. However, whether the body really makes more Acetylcholine just because you take supplements is questionable. If you still want to try Choline as a supplement in order to e.g. increase secretion production in mucous membranes, the recommended daily intake is 550 mg per day for men and 425 mg for women. Normally, you get this through your diet. If you want to test a higher dose, you should be aware that the upper limit of Choline supplementation is set at 3500 mg per day. Below is a list of preparations that could improve dry eye problems.
