NEET MDS Lessons
Pharmacology
Midazolam -Intravenous Anesthetics
Midazolam is a benzodiazepine used for preoperative sedation, induction of anesthesia, or maintenance of anesthesia in short procedures.
Seizure classification:
based on degree of CNS involvement, involves simple ( Jacksonian; sensory or motor cortex) or complex symptoms (involves temporal lobe)
1. Generalized (whole brain involved):
a. Tonic-clonic:
Grand Mal; ~30% incidence; unconsiousness, tonic contractions (sustained contraction of muscle groups) followed by clonic contractions (alternating contraction/relaxation); happens for ~ 2-3 minutes and people don’t breathe during this time
Drugs: phenytoin, carbamazepine, Phenobarbital, lamotrigine, valproic acid
Status epilepticus: continuous seizures; use diazepam (short duration) or diazepam + phenytoin
b. Absence:
Petit Mal; common in children; frequent, brief lapses of consciousness with or without clonic motor activity; see spike and wave EEg at 3 Hz (probably relates to thalamocorticoreverburating circuit)
Drugs: ethosuximide, lamotrigine, valproic acid
c. Myoclonic: uncommon; isolated clinic jerks associated with bursts of EEG spikes;
Drugs: lamotrigine, valproic acid
d. Atonic/akinetic: drop seizures; uncommon; sudden, brief loss of postural muscle tone
Drugs: valproic acid and lamotrigine
2. Partial: focal
a. Simple: Jacksonian; remain conscious; involves motor or sensory seizures (hot, cold, tingling common)
Drugs: carbamazepine, phenytoin, Phenobarbital, lamotrigine, valproic acid, gabapentin
b. Complex: temporal lobe or psychomotor; produced by abnormal electrical activity in temporal lobe (involves emotional functions)
Symptoms: abnormal psychic, cognitive, and behavioral function; seizures consist of confused/altered behavior with impaired consciousness (may be confused with psychoses like schizophrenia or dementia)
Drugs: carbamazepine, phenytoin, laotrigine, valproic acid, gabapentin
Generalizations: most seizures can’t be cured but can be controlled by regular administration of anticonvulsants (many types require treatment for years to decades); drug treatment can effectively control seizures in ~ 80% of patients
Ketoprofen
It acts by inhibiting the body's production of prostaglandin.
Warfarin (Coumadin):
- The most common oral anticoagulant.
- It is only active in vivo.
- Warfarin is almost completely bound to plasma proteins. -96% to 98% bound.
- Warfarin is metabolized by the liver and excreted in the urine.
- Coumarin anticoagulants pass the placental barrier and are secreted into the maternal milk.
- Newborn infants are more sensitive to oral anticoagulants than are adults because of lower vitamin K levels and lower rates of metabolism.
- Bleeding is the most common side effect and occurs most often from the mucous membranes of the gastrointestinal tract and the genitourinary tract.
Oral anticoagulants are contraindicated in:
• Conditions where active bleeding must be avoided, Vitamin K deficiency and severe
hepatic or renal disease, and where intensive salicylate therapy is required.
Excretion
Routes of drug excretion
The most important route of drug elimination from the body is via the kidney
Renal Drug Excretion
- Glomerular Filtration
- Passive Tubular Reabsorption: drugs that are lipid soluble undergo passive reabsorption from the tubule back into the blood.
- Active Tubular Secretion
Factors that Modify Renal Drug Excretion
- pH Dependent Ionization: manipulating urinary pH to promote the ionization of a drug can decrease passive reabsorption and hasten excretion.
- Competition for Active Tubular Transport
- Age: Infants have a limited capscity to excrete drugs.
Nonrenal Routes of Drug Excretion
Breast Milk
Bile, Lungs, Sweat and Saliva
The kidney is the major organ of excretion. The lungs become very important for volatile substances or volatile metabolites.
Drugs which are eliminated by the kidney are eliminated by:
a) Filtration - no drug is reabsorbed or secreted.
b) Filtration and some of the drug is reabsorbed.
c) Filtration and some secretion.
d) Secretion
By use of the technique of clearance studies, one can determine the process by which the kidney handles the drug.
Renal plasma clearance = U x V ml/min U / Cp = conc. of drug in urine
Cp = conc. of drug in plasma
V = urine flow in ml/min
Renal clearance ratio = renal plasma clearance of drug (ml/min) / GFR (ml/min)
Total Body Clearance = renal + non-renal
Heroin (diacetyl morphine)
Heroin is synthetically derived from the natural opioid alkaloid morphine
Largely owing to its very rapid onset of action and very short half-life, heroin is a popular drug of abuse
It is most effective when used intravenously
Heroin is rapidly deacetylated to 6-monoacetyl morphine and morphine, both of which are active at the mu opioid receptor
More lipid soluble than morphine and about 2½ times more potent. It enters the CNS more readily.
Immunosuppressive antibodies can be classified mainly into monoclonal and polyclonal antibodies, targeting specific components of the immune system.
-
Monoclonal Antibodies:
-
Basiliximab: Targets the IL-2 receptor on T cells, inhibiting T-cell activation. It is FDA approved for use in renal transplantation to prevent acute rejection.
-
Alemtuzumab: Targets CD52, a protein found on the surface of mature lymphocytes. It is used for treating chronic lymphocytic leukemia and as an induction agent in kidney transplantation.
-
Rituximab: Targets CD20 on B cells, leading to B-cell depletion. It is used in various conditions, including non-Hodgkin lymphoma and rheumatoid arthritis.
-
Daclizumab: Targets the IL-2 receptor (CD25) and is used in renal transplantation to prevent acute rejection.
-
Eculizumab: Targets complement component C5, inhibiting the complement cascade. It is used in conditions like paroxysmal nocturnal hemoglobinuria and atypical hemolytic uremic syndrome.
-
-
Polyclonal Antibodies:
-
Rabbit Antithymocyte Globulin (rATG): A polyclonal antibody that targets multiple T-cell surface markers, leading to T-cell depletion. It is used as an induction agent in kidney transplantation and for treating acute rejection.
-
Equine Antithymocyte Globulin (eATG): Similar to rATG, it targets T cells and is used in transplantation settings.
-
-
Mechanisms of Action:
-
Depletion of Immune Cells: Many antibodies work by depleting specific immune cell populations (e.g., T cells or B cells) to reduce the immune response against transplanted organs or in autoimmune diseases.
-
Blocking Activation Signals: Some antibodies block key receptors involved in T-cell activation, preventing the immune response from being initiated.
-
Inhibition of Complement Activation: Antibodies like eculizumab inhibit the complement system, which can contribute to tissue damage in antibody-mediated rejection.
-
-
Clinical Applications:
-
Organ Transplantation: Antibodies are commonly used to prevent rejection in kidney, liver, and heart transplants.
-
Autoimmune Diseases: They are also used in treating conditions like rheumatoid arthritis, lupus, and multiple sclerosis.
-
-
Potential Side Effects:
- Infections: Due to immune suppression, patients are at increased risk of infections.
- Allergic Reactions: Some patients may experience allergic reactions to antibody therapies.
- Infusion Reactions: These can occur during the administration of monoclonal antibodies, leading to symptoms like fever, chills, and hypotension.