EXCI461 Lecture Notes: Chapter 8 Skeletal Muscle Relaxants PDF

[EXCI461 Lecture Notes: Chapter 8 Skeletal Muscle Relaxants] ======================================================================== [**8.1 Objectives:** Describe the use of skeletal muscle relaxants and their side effects. Know the anticholinergic effects]. =======================================...

[EXCI461 Lecture Notes: Chapter 8 Skeletal Muscle Relaxants] ======================================================================== [**8.1 Objectives:** Describe the use of skeletal muscle relaxants and their side effects. Know the anticholinergic effects]. ========================================================================================================================================= - Skeletal muscle is one of three types of muscle, skeletal muscle is striated muscle tissue attached to bones via tendons, and under voluntary control. - Muscle fibers contract in response to acetylcholine, released at the cholinergic neuromuscular junction. - This is connected to the somatic nervous system, and under the influence of the autonomic nervous system (sympathetic and parasympathetic). [Picture explanations (anything before 1, would be considered centrally acting):] 1\. Presynaptic terminal 2\. Sarcolemma 3\. Synaptic vesicle 4\. Nicotinic acetylcholine receptor 5\. Mitochondria [8.2 Objectives: Describe peripheral and central skeletal muscle relaxants effects, know the anti-cholinergic side effects]. ======================================================================================================================================== [Peripheral versus central acting drugs]. ----------------------------------------------------- - There are many toxins and drugs that interfere with the cholinergic pathway (key modular pathway) either peripherally or centrally. - Peripheral action is when drug or toxin acts directly on some part of the neuromuscular junction. - Central action is when drug or toxin acts on the central nervous system (CNS) to suppress the action potentials that connect to the presynaptic terminal. [Botulism toxin is an example of a peripheral acting toxin and drug. ] -------------------------------------------------------------------------------------------------------- - *Clostridium botulinum:* - It is a bacteria pathogen that can grow and spread by spores. - Infections can cause coma and death if serious and untreated. - Botulism toxin is produced by the bacteria. - A toxin is a small molecule produced by a pathogen; it is poisonous. - Works by paralyzing the body before taking over - The peripheral action of botulism toxin is to inhibit the release of synaptic vesicle which prevents activity of the nicotinic acetylcholine receptor. - Botulism toxin is anti-cholinergic. A person infected is said to have botulism! [Drug versions of this toxin exist!] ------------------------------------------------ - Botulism toxin can be highly diluted to produce BoTox. - BoTox and related products can be used to treat many neuromuscular diseases, such as cerebral palsy, multiple sclerosis. - They may also treat disorders such as: - Facial twitching - Dystonia (permanent muscle contraction) - Excessive sweating - Chronic migraine - Side effects of botulism toxin, and BoTox overdose: - Decreased production of saliva: - Dry mouth and throat - Postural (orthostatic) hypotension: - Feeling faint upon standing due to decreased blood pressure - Decreased peristalsis and constipation - Lack of rhythmic contraction of the intestines (peristalsis) which leads to constipation - Decreased respiratory contractions: trouble breathing (dyspnea) - Can be fatal due to paralysis, coma, not breathing [Example of centrally acting drug: benzodiazepines] --------------------------------------------------------------- - These types of drug suppress activity in central nervous system. - Central action of benzodiazepines is to target the inhibitory gamma-aminobutyric acid (GABA) receptors - GABA'ss role is to suppress the system when needed to calm down the body - The drug acts as an agonist of an inhibitor. Stimulating an inhibitor will suppress brain functions. Like pressing brake on a car will stop the car. - The drug can be used to treat muscle spasms, disorders with muscle spasms, convulsions. - Also used as sedative for uncomfortable medical procedures such as internal probing and scopes. - Dependency can occur (addiction). - Also used for psychiatric conditions. - Prescribed for insomnia in elderly patients [Side effects of central suppression are similar to the anti-cholinergic effects: ] ----------------------------------------------------------------------------------------------- - Sedation, drowsiness - Dizziness - Blurred vision - Depression - Rarely, coma (death) - Constipation - Pupil dilation - Small increase in heart rate - Urinary problems (difficulty urinating) - Increased intraocular pressure, bad to combine with glaucoma - [Other drugs with anti-cholinergic effects:] - Anti-histamines found in allergy, cold medications - Opioid analgesics - Many psychiatric drugs - Atropine used in medical procedures or in motion sickness products (atropine blocks the acetylcholine receptor) - Alcohol Often the anti-cholinergic drug is combined in a mixed product with an analgesic and/or anti-inflammatory. These are okay to use if it is an approved product at the pharmacy. [An anti-cholinergic drug may be sold in a mixture with]: ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- - Aspirin - Codeine - Acetaminophen (Tylenol) - Caffeine (helps the body to pass the liver effectively) [Non-drug options used to treat muscle spasms and pain]: - Cryotherapy, - Moist heat, - Massage, - Stretching