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Local anesthetic agents are a class of drugs that block the transmission of nerve impulses in the local area where they are applied or injected. They are used in many medical procedures to reduce pain and discomfort.
Types of local anesthetic
Here are some of the most common types of local anesthetics:
1. Lidocaine (Xylocaine)
This is one of the most commonly used local anesthetics. It has rapid onset of action (1-3 minutes when injected and 5-10 minutes when applied topically) and medium duration (1-2 hours).
2. Mepivacaine (Carbocaine)
It has a rapid onset (approximately 5 minutes) and a duration of action about 2-3 hours. Mepivacaine is often used in dental procedures.
3. Bupivacaine (Marcaine)
Bupivacaine has a slower onset (5-10 minutes), but its duration of action is long (4-7 hours), making it suitable for procedures that require long-lasting pain control.
4. Procaine (Novocain)
Procaine is an older drug with a slow onset of action (15-20 minutes) and short duration (30-60 minutes). It is not commonly used today.
5. Prilocaine (Citanest)
Prilocaine has a moderate onset and duration of action. It’s commonly used in dentistry.
6. Ropivacaine (Naropin)
Ropivacaine is a long-acting local anesthetic often used in regional anesthesia for surgery and for postoperative pain control.
Working of local anesthetic
Local anesthetics work by blocking sodium channels in the nerve cell membrane, preventing the propagation of the nerve impulse along the nerve. This in turn prevents the sensation of pain from reaching the brain.
The exact properties (like the speed of onset, duration of action, and strength of the anesthetic effect) depend on factors such as the specific drug used, the dosage, the addition of other substances like vasoconstrictors (which can prolong the effect), and the type of nerve fibers being targeted.
Local anesthetics are generally safe, but they can cause side effects. At the site of injection, there may be pain, swelling, or bruising. Systemic side effects can include dizziness, tremors, blurred vision, and, in rare cases, serious problems like seizures or cardiac arrest.
It’s also important to note that some people may have allergies to specific local anesthetics, which can cause symptoms like skin rashes, itching, difficulty breathing, and swelling of the face, lips, tongue, or throat. In such cases, an alternative anesthetic can be used.
Myasthenia gravis is a chronic autoimmune neuromuscular disease characterized by weakness and rapid fatigue of any of the voluntary muscles. It’s caused by a defect in the transmission of nerve impulses to muscles, due to the presence of antibodies that block acetylcholine receptors at the neuromuscular junction, inhibiting the excitatory effects of the neurotransmitter acetylcholine on nicotinic receptors at postsynaptic membranes.
The main goals of treatment are to increase neuromuscular transmission and to suppress the autoimmune response.
Drugs used in myasthenia gravis
Several types of medications can be used to help manage myasthenia gravis:
1. Anticholinesterase agents
These medications improve neuromuscular transmission and increase muscle strength. They work by inhibiting acetylcholinesterase, the enzyme that breaks down acetylcholine at the neuromuscular junction. This allows acetylcholine to accumulate and repeatedly stimulate the muscle fibers. Pyridostigmine (Mestinon) is the most commonly used anticholinesterase medication.
Corticosteroids like prednisone help to improve muscle strength by suppressing the production of abnormal antibodies. They are powerful anti-inflammatory drugs.
These drugs suppress the body’s immune system, reducing the production of antibodies that cause myasthenia gravis. Examples include azathioprine (Imuran), cyclosporine (Neoral, Sandimmune) and mycophenolate mofetil (CellCept).
4. Monoclonal antibodies
These are newer targeted therapies. Rituximab (Rituxan) targets B cells, reducing the production of the abnormal antibodies that are causing symptoms. Eculizumab (Soliris) is another monoclonal antibody that inhibits the immune system’s complement pathway, which is overactive in people with myasthenia gravis.
5. IVIG and Plasmapheresis
Intravenous immune globulin (IVIG) and plasmapheresis are often used as short-term treatments for severe, acute symptoms of myasthenia gravis. IVIG provides the body with normal antibodies, which can alter the immune system response. Plasmapheresis is a procedure that removes the abnormal antibodies from the blood and replaces the blood with normal body fluids or donated blood.
It’s important to note that some medications can exacerbate symptoms of myasthenia gravis or cause a myasthenic crisis, a life-threatening condition characterized by weakness of the respiratory muscles. These include certain antibiotics (such as aminoglycosides and fluoroquinolones), beta-blockers, calcium channel blockers, and some anti-arrhythmic drugs.
Glaucoma is a group of eye conditions that damage the optic nerve, often due to an abnormally high pressure in your eye, and it’s one of the leading causes of blindness for people over 60 years old. There are different types of glaucoma, including open-angle glaucoma and angle-closure glaucoma.
Drugs used in glaucoma
Medications, specifically eye drops, are often the first step in treatment. They aim to decrease eye pressure, and the approach depends on whether the glaucoma is open-angle or angle-closure. Here are some of the common classes of medications used in treating glaucoma:
These drugs increase the outflow of the fluid in your eye (aqueous humor). They may cause changes in eye color and eyelash length, and can darken the skin around the eyes. Examples include latanoprost (Xalatan), bimatoprost (Lumigan), and travoprost (Travatan Z).
2. Beta blockers
These reduce the production of fluid in the eye, thereby lowering the pressure in the eye. Examples include timolol (Timoptic), betaxolol (Betoptic), and levobunolol (Betagan). These drugs can slow the heartbeat and cause reduced blood pressure, fatigue, and erectile dysfunction.
3. Alpha-adrenergic agonists
These medications reduce the production of aqueous humor and increase the outflow of the fluid in the eye. Examples include apraclonidine (Iopidine) and brimonidine (Alphagan). They can cause irregular heart rate, high blood pressure, fatigue, and red, itchy or swollen eyes.
4. Carbonic anhydrase inhibitors
These medications reduce the production of fluid in the eye. They are also available in pill form, but they’re more commonly given as eye drops. Examples include dorzolamide (Trusopt) and brinzolamide (Azopt). Possible side effects include frequent urination, tingling in the fingers and toes, depression, stomach upset, kidney stones, and a metallic taste when consuming carbonated drinks.
5. Rho kinase inhibitors
These are a newer type of glaucoma drug which work by increasing the outflow of the fluid in the eye. An example is netarsudil (Rhopressa).
These drugs increase the outflow of fluid in the eye. They’re often used for certain types of glaucoma, such as angle-closure glaucoma. An example is pilocarpine.
7. Combination medications
Some eye drops contain more than one type of medication. This can be more convenient than taking multiple medications and can potentially reduce the risk of missing doses. Examples include dorzolamide and timolol (Cosopt), brimonidine and timolol (Combigan), and brinzolamide and brimonidine (Simbrinza).
In addition to medications, surgical procedures can be used to lower eye pressure, especially when medications are not enough or not well tolerated. These can involve making a small incision in the eye to help drain excess fluid, or they can involve the use of lasers to increase the outflow or decrease the production of the fluid.