Amoxicillin

a moderate-spectrum

β-lactam antibiotic used to treat bacterial infections caused by susceptible

Mode of action Amoxicillin acts by inhibiting the synthesis of bacterial cell walls. It inhibits cross-linkage between the linear peptidoglycan polymer chains that make up a major component of the cell wall of Gram-positive bacteria. microorganisms. It is usually the drug of choice within the class because it is better absorbed, following oral administration, than other beta-lactam antibiotics. Amoxicillin is susceptible to degradation by  β-lactamase-producing bacteria, and so is often given clavulanic acid.

Microbiology Amoxicillin is a moderate-spectrum antibiotic active against a wide range of Gram-positive, and a limited range of Gram-negative organisms

Susceptible Gram-positive organisms : Streptococcus spp., Diplococcus pneumoniae, non β-lactamase-producing Staphylococcus spp., and Streptococcus faecalis.

Susceptible Gram-negative organisms  Haemophilus influenzae, Neisseria gonorrhoeae, Neisseria meningitidis, Escherichia coli, Proteus mirabilis and Salmonella spp.

Resistant organisms Penicillinase producing organisms, particularly penicillinase producing Staphylococcus spp. Penicillinase-producing N. gonorrhoeae and H. influenzae are also resistant

All strains of Pseudomonas spp., Klebsiella spp., Enterobacter spp., indole-positive

Proteus spp., Serratia marcescens, and Citrobacter spp. are resistant.

The incidence of β-lactamase-producing resistant organisms, including E. coli, appears to be increasing.

Amoxicillin and Clavulanic acid Amoxicillin is sometimes combined with clavulanic acid, a β-lactamase inhibitor, to increase the spectrum of action against

Gram-negative organisms, and to overcome bacterial antibiotic resistance mediated through β-lactamase production.

Effects and Toxic Actions on Organ Systems

1. Local anesthetics (dose dependent) interfere with transmission in any excitable tissue (e.g. CNS and CVS).

2. CNS effects

 a. Central neurons very sensitive.

 b. Excitatory-dizziness, visual and auditory disturbances, apprehension, disorientation and muscle twitching more common with ester type agents.

 c. Depression manifested as slurred speech, drowsiness and unconsciousness more common with amide type agents (e.g. lidocaine).

 d. Higher concentrations of local anesthetic may eventually produce tonic-clonic[grand mal]  convulsions.

 e. Very large doses may produce respiratory depression which can be fatal. Artificial respiration may be life-saving.

 3.CVS effects

 a. Local anesthetics have direct action on the myocardium and peripheral vasculature by closing the sodium channel, thereby limiting the inward flux of sodium ions.

 b. Myocardium usually depressed both in rate and force of contraction. Depression of ectopic pacemakers useful in treating cardiac arrhythmias.

 c. Concentrations employed clinically usually cause vasodilation in area of injection.

 d. Vasoconstrictors such as epinephrine may counteract these effects on myocardium and vasculature.

4.  Local Tissue Responses

 a. Occasionally focal necrosis in skeletal muscle at injection site, decreased cell motility and delayed wound healing.

 b. Tissue hypoxia may be produced by action of excessive amounts of vasoconstrictors.

Gentamicin

Gentamicin is a aminoglycoside antibiotic, and can treat many different types of bacterial infections, particularly Gram-negative infection.

Gentamicin works by binding to a site on the bacterial ribosome, causing the genetic code to be misread.

Like all aminoglycosides, gentamicin does not pass the gastro-intestinal tract, so it can only be given intravenously or intramuscularly.

Gentamicin can cause deafness or a loss of equilibrioception in genetically susceptible individuals. These individuals have a normally harmless mutation in their DNA, that allows the gentamicin to affect their cells. The cells of the ear are particularly sensitive to this.

Gentamicin can also be highly nephrotoxic, particularly if multiple doses accumulate over a course of treatment. For this reason gentamicin is usually dosed by body weight. Various formulae exist for calculating gentamicin dosage. Also serum levels of gentamicin are monitored during treatment.

E. Coli has shown some resistance to Gentamicin, despite being gram-negative

Characteristics of Opioid Receptors

mu₁

Agonists : morphine phenylpiperidines

Actions:  analgesia bradycardia sedation

mu₂

Agonists : morphine phenylpiperidines

Actions:  respiratory depression euphoria physical dependence  

delta

Actions:  analgesia-weak,  respiratory depression

kappa

Agonists: ketocyclazocine dynorphin nalbuphine butorphanol

Actions:  analgesia-weak respiratory depression sedation

Sigma

Agonists: pentazocine

Action: dysphoria -delerium hallucinations tachycardia hypertension

epsilon:

Agonists: endorphin

Actions: stress response acupuncture

Different Systems of the CNS & their functions

These systems are pathways formed of specific parts of the brain and the neurons connecting them. 

They include:
1.The pyramidal system 
2.The extrapyramidal system 
3.The limbic system 
4.The reticular formation 
5.The tuberohypophyseal system

The pyramidal system: 

It originates from the motor area of the cerebral cortex and passes through the spinal cord, therefore it is also known as the “corticospinaltract”. 
It is responsible for the regulation of the fine voluntary movements.

The extrapyramidal system: 

It also controls the motor functionbut involves areas other than the corticospinal tract. 
It is involved in the regulation of gross voluntary movements, thus it complements the function of the pyramidal system. 

The “basal ganglia” constitute an essential part of this system. 

Degenerative changes in the pathway running from the “substantianigra”to the “corpus striatum”(or nigrostriatal pathway) may cause tremors and muscle rigidity characteristic of “Parkinson’s disease”.

The limbic system: 

The major parts of this system are: the hypothalamus, the basal ganglia, the hippocampus(responsible for short term memory), and some cortical areas. 

The limbic system is involved in the control of “behavior”& “emotions”.

The reticular formation:

It is composed of interlacing fibers and nerve cells that run in all directions beginning from the upper part of the spinal cord and extending upwards. 
It is important in the control of “consciousness” and “wakefulness”.

The tuberohypophyseal system: 

It is a group of short neurons running from the hypothalamusto the hypophysis(pituitary gland) regulating its secretions.
 

CLASSICATION OF ANTICOAGULANT DRUGS

1. Direct Acting Anticoagulants

a) Calcium Chelators (sodium citrate, EDTA)

b) Heparin

2. Indirect Acting Anticoagulant Drugs

a) Warfarin