NEET MDS Lessons
Pharmacology
Streptomycin
Streptomycin was the first of a class of drugs called aminoglycosides to be discovered, and was the first antibiotic remedy for tuberculosis. It is derived from the actinobacterium Streptomyces griseus.
Streptomycin cannot be given orally, but must be administered by regular intramuscular injection.
Glitazones (thiazolidinediones)
Thiazolidinediones, also known as the "-glitazones"
pioglitazone
rosiglitazone
Mechanism
bind to nuclear receptors involved in transcription of genes mediating insulin sensitivity
peroxisome proliferator-activating receptors (PPARs)
↑ insulin sensitivity in peripheral tissue
↓ gluconeogenesis
↑ insulin receptor numbers
↓ triglycerides
Clinical use
type II DM
as monotherapy or in combination with other agents
contraindicated in CHF
associated with increased risk of MI (in particular rosiglitazone)
Oxycodone
About equal potency to morphine. Very effective orally.
It is combined with aspirin or acetaminophen for the treatment of moderate pain and is available orally
Oxycodone is a semisynthetic compound derived from thebaine, with agonist activity primarily at mu receptors.
Doxycycline
Commonly prescribed for infections and to treat acne. treat urinary tract infections, gum disease, and other bacterial infections such as gonorrhea and chlamydia., as a prophylactic treatment for infection by Bacillus anthracis (anthrax). It is also effective against Yersinia pestis and malaria.
Anticonvulsant Drugs
A. Anticonvulsants: drugs to control seizures or convulsions in susceptible people
B. Seizures: abnormal neuronal discharges in the nervous system produced by focal or generalized brain disturbances
Manifestations: depend on location of seizure activity (motor cortex → motor convulsions, sensory cortex → abnormal sensations, temporal cortex → emotional disturbances)
Causes: many brain disorders such as head injury (glial scars, pH changes), anoxia (changes in pH or CSF pressure), infections (tissue damage, high T), drug withdrawal (barbiturates, ethanol, etc.), epilepsy (chronic state with repeated seizures)
C. Epilepsy: most common chronic seizure disorder, characterized by recurrent seizures of a particular pattern, many types (depending on location of dysfunction)
Characteristics: chronic CNS disorders (years to decades), involve sudden and transitory seizures (abnormal motor, autonomic, sensory, emotional, or cognitive function and abnormal EEG activity)
Etiology: hyperexcitable neurons; often originate at a site of damage (epileptogenic focus), often found at scar tissue from tumors, strokes, or trauma; abnormal discharge spreads to normal brain regions = seizure
Idiopathic (70%; may have genetic abnormalities) and symptomatic epilepsy (30%; obvious CNS trauma, neoplasm, infection, developmental abnormalities or drugs)
Neuropathophysiology: anticonvulsants act at each stage but most drugs not effective for all types of epilepsy (need specific drugs for specific types)
Seizure mechanism: enhanced excitation (glutamate) or ↓ inhibition (GABA) of epileptic focus → fire more quickly → ↑ release of K and glutamate → ↑ depolarization of surrounding neurons (=neuronal synchronization) → propagation (normal neurons activated)
Methadone
Pharmacology and analgesic potency similar to morphine.
- Very effective following oral administration.
- Longer duration of action than morphine due to plasma protein binding (t1/2 approximately 25 hrs).
- Used in methadone maintenance programs for drug addicts and for opiate withdrawal. Opiate withdrawal is more prolonged but is less intense than it is following morphine or heroin.
Class III Potassium Channel Blockers
Prolong effective refractory period by prolonging Action Potential
Treatment: ventricular tachycardia and fibrillation, conversion of atrial fibrillation or flutter to sinus rhythm, maintenance of sinus rhythm
– Amiodarone (Cordarone) – maintenance of sinus rhythm
– Bretylium (Bretylol)
– Ibutilide (Corvert)
– Dofetilide (Tykosyn)
– Sotalol (Betapace)
Amiodarone
- Has characteristics of sodium channel blockers, beta blockers, and calcium channel blockers
- Has vasodilating effects and decreases systemic vascular resistance
- Prolongs conduction in all cardiac tissue
- Decreases heart rate
- Decreases contractility of the left ventricles
Class III - Adverse Effects
- GI- Nausea vomiting and GI distress
- CNS- Weakness and dizziness
- CV-Hypotension, CHF, and arrhythmias are common.
- Amiodarone associated with potentially fatal Hepatic toxicity, ocular abnormalities and serious cardiac arrhythmias.
Drug – Drug Interactions
These drugs can cause serious toxic effects if combined with digoxin or quinidine.