NEET MDS Lessons
Pharmacology
BETA-LACTAM ANTIBIOTICS
β-lactam antibiotics are a broad class of antibiotics including penicillin derivatives, cephalosporins, monobactams, carbapenems and β-lactamase inhibitors; basically any antibiotic agent which contains a β-lactam nucleus in its molecular structure. They are the most widely used group of antibiotics available.
Mode of action All β-lactam antibiotics are bactericidal, and act by inhibiting the synthesis of the peptidoglycan layer of bacterial cell walls.β-lactam antibiotics were mainly active only against Gram-positive bacteria, the development of broad-spectrum β-lactam antibiotics active against various Gram-negative organisms has increased the usefulness of the β-lactam antibiotics.
Common β-lactam antibiotics
Penicillins
Narrow spectrum penicillins:
benzathine penicillin
benzylpenicillin (penicillin G)
phenoxymethylpenicillin (penicillin V)
procaine penicillin
Narrow spectrum penicillinase-resistant penicillins
methicillin
dicloxacillin
flucloxacillin
Moderate spectrum penicillins :
amoxicillin, ampicillin
Broad spectrum penicillins :
co-amoxiclav (amoxycillin+clavulanic acid)
Extended Spectrum Penicillins:
piperacillin
ticarcillin
azlocillin
carbenicillin
Neuron Basic Structure (How brain cells communicate)
• Synapse:A junction between the terminal button of an axon and the membrane of another neuron
• Terminal button(orbouton):The bud at the end of a branch of an axon; forms synapses with another neuron; sends information to that neuron.
• Neurotransmitter:A chemical that is released by a terminal button; has an excitatory or inhibitory effect on another neuron.
Different types of Synapses
1-Axo-denrdritic
2-Axo-axonal
3-Axo-somatic
Chemical transmission in the CNS
The CNS controls the main functions of the body through the action endogenous chemical substances known as “neurotransmitters”.
These neurotransmitters are stored in and secreted by neurons to “transmit”information to the postsynaptic sites producing either excitatoryor inhibitory responses.
Most centrally acting drugs exert their actions at the synaptic junctions by either affecting neurotransmitter synthesis, release, uptake, or by exerting direct agonistor antagonistaction on postsynaptic sites.
Erythromycin
used for people who have an allergy to penicillins. For respiratory tract infections, it has better coverage of atypical organisms, including mycoplasma. It is also used to treat outbreaks of chlamydia, syphilis, and gonorrhea.
Erythromycin is produced from a strain of the actinomyces Saccaropolyspora erythraea, formerly known as Streptomyces erythraeus.
Antidiarrheal
Antidiarrheal drugs may be given to relieve the symptom (non-specific therapy) or may be given to treat the underlying cause of the symptom (specific therapy).
Ι. Drugs used for the symptomatic (non-specific) treatment of diarrhoea include:
• Opiates and opiate derivatives are the most effective (such as morphine), but it is not used because of potentially serious adverse effects. Other agents, such as diphenoxylate and loperamide, are commonly used.
• Adsorbent – demulcent products such as kaolin – pectin preparation may be included in antidiarrheal preparations. Unfortunately, they may adsorb nutrients and other drugs, including the antidiarrheal agents if given concurrently.
• Anticholinergic agents e.g. atropine is occasionally used to decrease abdominal cramping and pain associated with diarrhoea.
ΙΙ. Specific therapy may include the use of antibacterial agents that are recommended for use in carefully selected cases of bacterial enteritis. For example, severe diarrhoea by salmonella, shigella, campylobacter and clostridia species can be treated by antibiotics (ampicillin, chloramphenicol, co-trimoxazole).
Other sedatives: carisoprodol, cyclobenzaprine, and methocarbamol are used for muscle relaxation.
Baclofen
1. Used in spasticity states to relax skeletal muscle.
2. Occasionally used in trigeminal neuralgia.
Antihistamines (first-generation H1 receptor blockers)
1. Used for sedation (e.g., diphenhydramine).
Ethyl alcohol
DIURETICS
|
Specific Therapeutic Objective |
Clinical State(s) |
Drug(s) (Class) |
|
Draw fluid from tissue to vascular space reduce tissue edema |
Cerebral edema |
Mannitol (Osmotic) |
|
Decrease renal swelling |
Renal shutdown |
Glucose (Osmotic) |
|
Modest and/or sustained decrease in venous hydrostatic pressure |
Congestive heart failure |
Hydrochlorothiazide (thiazide) |
|
Aggressive and/or short-term decrease in venous hydrostatic pressure |
Congestive heart failure |
Furosemide (loop) |
|
Inhibit aldosterone action |
Hepatic cirrhosis |
triamterene (K+ sparing) |
|
Reduce potassium wasting 2o to other diuretic |
Hepatic cirrhosis |
triamterene (K+ sparing) |
|
Inhibit ADH action |
Inappropriate ADH secretion |
lithium (aquaretic) |
|
Increase calcium secretion |
Malignant hypercalcemia
|
Furosemide (loop) |
|
Reduce urine output |
Diabetes insidpidus |
Hydrochlorothiazide (thiazide) |
|
Urine alkalinization |
Various |
Carbonic anhydrase inhibitors |
Metabolism
Hepatic Drug-Metabolizing Enzymes: most drug metabolism in the liverperformed by the hepatic microsomal enzyme system.
Therapeutic Consequences of Drug Metabolism
- Accelerated Renal Drug Excretion: The most important consequence of drug metabolism is the promotion of renal drug excretion. Metabolism makes it possible for the kidney to excrete many drugs that it otherwise could not.
- Drug Inactivation
- Increased Therapeutic Action: Metabolism may increase the effectiveness of some drugs.
- Activation of Prodrugs: A prodrug is a compound that is inactive when administered and made active by conversion in the body.
- Increased or Decreased Toxicity
Factors that influence rate of metabolism:
- Age: Hepatic maturation doesn't occur until about a year old.
- Induction of Drug-Metabolizing Enzymes: Some drugs can cause the rate of metabolism to increase, leading to the need for an increased dosage. May also influence the rate of metabolism for other drugs taken at the same time, leading to a need for increased dosages of those drugs as well.
- First-Pass Effect: Hepatic inactivation of certain oral drugs. Avoided by parentaral administration of drugs that undergo rapid hepatic metabolism.
- Nutritional Status
- Competition between Drugs