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.

Mechanism of action Erythromycin prevents bacteria from growing, by interfering with their protein synthesis. Erythromycin binds to the subunit 50S of the bacterial ribosome, and thus inhibits the translocation of peptides.

Erythromycin is easily inactivated by gastric acids, therefore all orally administered formulations are given as either enteric coated or as more stable salts or  esters. Erythromycin is very rapidly absorbed, and diffused into most tissues and  phagocytes. Due to the high concentration in phagocytes, erythromycin is actively transported to the site of infection, where during active phagocytosis, large concentrations of erythromycin are released.

Most of erythromycin is metabolised by demethylation in the liver. Its main route elimination route is in the bile, and a small portion in the urine.

Erythromycin's half-life is 1.5 hours.

Side-effects. More serious side-effects, such as reversible deafness are rare. Cholestatic jaundice, Stevens-Johnson syndrome and toxic epidermal necrosis are some other rare side effects that may occur.

Contraindications Earlier case reports on sudden death prompted a study on a large cohort that confirmed a link between erythromycin, ventricular tachycardia and sudden cardiac death in patients also taking drugs that prolong the metabolism of erythromycin (like verapamil or diltiazem)

erythromycin should not be administered in patients using these drugs, or drugs that also prolong the QT time.

Estimation of the risk of anesthesia (American Society of Anesthesiologists scale)

• ASA 1: healthy patient.

• ASA 2: patient with stable, treated illness like arterial hypertension, diabetes melitus, asthma bronchiale, obesity

• ASA 3: patient with systemic illness decreasing sufficiency like heart illness, late infarct

• ASA 4: patient with serious illness influencing his state like renal insuficiency, unstable hypertension, circulatory insuficiency

• ASA 5: patient in life treatening illness

• ASA 6: brain death- potential organ donor

PSEUDOEPHEDRINE

Pseudoephedrine appears to have less pressor activity and weaker central nervous system effects than ephedrine. It has agonist activity at both β1  and β2 adrenoceptors, leading to increased cardiac output and relaxation of bronchial smooth muscle.

Pseudoephedrine is rapidly absorbed throughout the body. It is eliminated largely unchanged in urine by N-demethylation.

It is indicated in symptomatic relief from stuffed nose, respiratory tract congestion, bronchospasm associated with asthma, bronchitis and other similar disorders.

Cells of the Nervous System 

1-Neurons (Nerve Cells):function units of the nervous system by conducting nerve impulses, highly specialized and amitotic. Each has a cell body (soma), one or more dendrites, and a single axon. 
• Cell Body: it has a nucleus with at least one nucleolus and many of the typical cytoplasmic organelles, but lacks centriolesfor cell division. 

• Dendrites:Dendrites and axons are cytoplasmic extensions (or processes), that project from the cell body. They are sometimes referred to as fibers. Dendrites (afferent processes) increase their surface area to receive signals from other neurons, and transmit impulses to the neuron cell body. 

• Axon: There is only one axon (efferent process) that projects from each cell body.        
It carries impulses away from the cell body.

2-Glial cells: do not conduct nerve impulses, but support, nourish, and protect the neurons. They are mitotic, and far more numerous than neurons. 

Astrocyte: A glialcell that provides support for neurons of the CNS, provides nutrients regulates the chemical composition of the extracellularfluid.

• Oligodendrocyte: A type of glialcell in the CNS that forms myelin sheaths.

• Microglia:The smallest glialcells; act as phagocytes (cleaning up debris) and protect the brain from invading microorganisms.

• Schwann cell:A cell in the PNS that is wrapped around a myelinatedaxon, providing one segment of its myelin sheath.

Codeine

Codeine is methyl morphine, with a methyl substitution on the phenolic hydroxyl group of morphine. It is more lipophilic than morphine and thus crosses the blood–brain barrier faster.

• classified as a simple, or mild analgesic, codeine is often used in low doses as an oral analgesic has a much better oral/parenteral absorption ratio than morphine.
• Effective for mild to moderate pain.
• Constipation occurs
• Dizziness may occur in ambulatory patients.
• More potent histamine-releasing action than does morphine.
• Should not be administered by IV injection.
• Extremely effective antitussive agent and is used therapeutically for suppressing cough.
• In contrast to morphine, codeine overdose can occasionally lead to the production of seizures.
• Seizures can be treated with barbiturates.
• Respiratory depression can be counteracted with Naloxone.
• orally, 30 mg of codeine is equi-analgesic to 600 mg of aspirin, however, the effects of the two are additive, and occasionally synergistic

VITAMIN -K

• Group of lipophilic, hydrophobic vitamins.
• Needed for the post-translational modification of coagulation proteins.
• Phylloquinone (vitamin K1) is the major dietary form of vitamin K.

• Vitamin K2 (menaquinone, menatetrenone) is produced by bacteria in the intestines.