Viagra / Sildenafil

Systematic (IUPAC) name
1-[4-ethoxy-3-(6,7-dihydro-1-methyl-7-oxo-3-propyl-1H-pyrazolo[4,3-d]pyrimidin-5-yl) phenylsulfonyl]-4-methylpiperazine citrate

Formula C22H30N6O4S
Mol. mass base: 474.6g/mol
Bioavailability 40%
Metabolism Hepatic
Half life 3-4hRoutesOral

Sildenafil citrate, sold under the names Viagra, Revatio and under various other names, is a drug used to treat male erectile dysfunction (impotence) and pulmonary arterial hypertension (PAH), developed by the pharmaceutical company Pfizer. Its primary competitors on the market are tadalafil (Cialis), and vardenafil (Levitra)..
Mechanism of action
Part of the physiological process of erection involves the parasympathetic nervous system causing the release of nitric oxide (NO) in the corpus cavernosum of the penis. NO binds to the receptors of the enzyme guanylate cyclase which results in increased levels of cyclic guanosine monophosphate (cGMP), leading to smooth muscle relaxation (vasodilation) of the intimal cushions of the helicine arteries, resulting in increased inflow of blood and an erection.
Sildenafil is a potent and selective inhibitor of cGMP specific phosphodiesterase type 5 (PDE5) which is responsible for degradation of cGMP in the corpus cavernosum. The molecular structure of sildenafil is similar to that of cGMP and acts as a competitive binding agent of PDE5 in the corpus cavernosum, resulting in more cGMP and better erections. Without sexual stimulation, and therefore lack of activation of the NO/cGMP system, sildenafil should not cause an erection. Other drugs that operate by the same mechanism include tadalafil (Cialis) and vardenafil (Levitra).
Sildenafil is metabolised by hepatic enzymes and excreted by both the liver and kidneys. If taken with a high-fat meal, there may be a delay in absorption of sildenafil and the peak effect might be reduced slightly as the plasma concentration will be lowered.
Dosage and price
As with all prescription drugs, proper dosage is at the discretion of a licensed medical doctor. The dose of sildenafil for erectile dysfunction is 25 mg to 100 mg taken not more than once per day between 30 minutes and 4 hours prior to sexual intercourse.

It is usually recommended to start with a dosage of 50 mg and then lower or raise the dosage as appropriate. The drug is sold in three dosages (25, 50, and 100 mg), all three costing about US$10 per pill. Name-brand Viagra sildenafil is not scored and a fairly hard coating makes it more difficult to accurately cut the pills in half, even with a pill cutter. The dosage for pulmonary arterial hypertension (Revatio) is one 20 mg tablet three times a day. Viagra pills are blue and diamond-shaped with the words "Pfizer" engraved on one side, and "VGR xx" (where xx stands for "25", "50" or "100", the dose of that pill in milligrams) engraved on the other. Words are not printed on the pills. Revatio pills, which are used for PAH, are white, round, film-coated tablets imprinted with "RVT 20" on one side and "Pfizer" on the other.
Contraindications
Contraindications include:
· When taking nitric oxide donors, organic nitrites and nitrates, such as glyceryl trinitrate (nitroglycerin), sodium nitroprusside, amyl nitrite ("poppers")[6]
· In men for whom sexual intercourse is inadvisable due to cardiovascular risk factors
· Severe hepatic impairment (decreased liver function)
· Severe impairment in renal function
· Hypotension (low blood pressure)
· Recent stroke or heart attack
· Hereditary degenerative retinal disorders (including genetic disorders of retinal phosphodiesterases)
Chemical synthesis
The preparation steps for synthesis of Viagra (sildenafil citrate) are as follows:
1. Methylation of 3-propylpyrazole-5-carboxylic acid ethyl ester with hot dimethyl sulfate.
2. Hydrolysis with aqueous NaOH to free acid.
3. Nitration with oleum/fuming nitric acid.
4. Carboxamide formation with refluxing thionyl chloride/NH4OH.
5. Reduction of nitro group to amino.
6. Acylation with 2-ethoxybenzoyl chloride.
7. Cyclization.
8. Sulfonation to the chlorosulfonyl derivative.
9. Condensation with 1-methylpiperazine.

Gentamicin

Systematic (IUPAC) name
2-[4,6-diamino-3- [3-amino-6-(1-methylaminoethyl) tetrahydropyran-2-yl] oxy-2-hydroxy- cyclohexoxy]-5-methyl- 4-methylamino-tetrahydropyran-3,5-dio

Excretion renal
Half life 2 hours
Routes IV/IM
Protein binding 0-10%
Bioavailability limited oral bioavailability
FormulaC21H43N5O7
Mol. mass 477.596 g/mol



Molecular model showing how Gentamicin binds to bacterial DNA
Gentamicin is an aminoglycoside antibiotic, used to treat many types of bacterial infections, particularly those caused by Gram-negative bacteria. However, gentamicin is not used for Neisseria gonorrhoeae, Neisseria meningitidis or Legionella pneumophila bacterial infections.
It is synthesized by Micromonospora, a genus of Gram-positive bacteria widely present in the environment (water and soil). To highlight their specific biological origins, gentamicin and other related antibiotics produced by this genus (verdamicin, mutamicin, sisomicin, netilmicin, retymicin) have generally their spellings ending in ~micin and not in ~mycin. Gentamicin is a bactericidal antibiotic that works by binding the 50S subunit of the bacterial ribosome, interrupting protein synthesis.


Like all aminoglycosides, when gentamicin is given orally, it is not systemically active. This is because it is not absorbed to any appreciable extent from the small intestine. It appears to be completely eliminated unchanged in the urine. Urine must be collected for many days to recover all of a given dose because the drug binds avidly to certain tissues. It is administered intravenously, intramuscularly or topically to treat infections.

E. coli has shown some resistance to gentamicin, despite being Gram-negative. Gentamicin is one of the few heat-stable antibiotics that remain active even after autoclaving, which makes it particularly useful in the preparation of certain microbiological growth media.Treatment of susceptible bacterial infections, normally Gram-negative bacteria including Pseudomonas, Proteus, Serratia, and Gram-positive Staphylococcus.

Side effects
All aminoglycosides are toxic to the sensory cells of the ear, but they vary greatly in their relative effects on hearing versus balance. Gentamicin is a vestibulotoxin, and can cause permanent loss of equilibrioception, caused by damage to the vestibular apparatus of the inner ear if taken at high doses or for prolonged periods of time. Gentamicin has on occasion impaired or even wholly destroyed hearing. In most instances, the affected individual has undergone treatment for 2 weeks or more. A small number of affected individuals have a normally harmless mutation in their mitochondrial RNA, that allows the gentamicin to affect their cells. The cells of the ear are particularly sensitive to this. Gentamicin is sometimes used intentionally for this purpose in severe Ménière's disease, to disable the vestibular apparatus.
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 trough and peak serum levels of gentamicin are monitored during treatment, generally before and after the third dose is infused. Gentamicin, like other aminoglycosides, causes nephrotoxicity by inhibiting protein synthesis in renal cells. This mechanism specifically causes necrosis of cells in the proximal tubule, resulting in acute tubular necrosis which can lead to acute renal failure.
From Wikipedia, the free encyclopedia

Doxycyclin

Doxycyclin structural formula:
Molecular formula is C22H24N2O8-
Chemical IUPAC Name is 2-(amino-hydroxy-methylidene)-4-dimethylamino-5,10,11,12a-tetrahydroxy-6-methyl- 4a,5,5a,6-tetrahydro-4H-tetracene-1,3,12-trione-
Molecular weight is 444.435 g/mol
Generic name: Doxycycline

Brand name(s):
Atridox, Doryx, Doxychel, Doxychel Hyclate, Doxycin, Doxylin, Doxytec, Doxytetracycline, Jenacyclin, Monodox, Novo-Doxylin, Nu-Doxycycline, Periostat, Supracyclin, Vibramycin


Some kinds of bacteria are not easily treatable by the body’s built-in defenses. That is why the use of medicine is often required to stop the growth and spread of certain bacteria that may enter the body. Doxycyclin is one of the prescription medicines that serve such purpose. Doxycyclin is a tetracycline-type of synthetic antibiotic that is used to treat several bacterial infections including Gonorrhea and Chlamydia. It is also found extremely helpful in managing acnes. Doxycyclin’s primary purpose is to stop the growth of bacteria. As such, it is an effective preventive measure against Malaria. Doxycyclin capsules are developed by world-renowned Pfizer Inc. in 1960. It was FDA-approved before 1970 and is widely used soon afterwards. Several bacteriologic testing would determine whether Doxycyclin is appropriate to treat your type of bacterial infection or not. It is also ideal that you check with your doctor regarding any allergic reaction that may occur or any other condition that may worsen upon the drug intake. Also, correct diagnosis of your disease is important for proper prescription. If used for the wrong reasons, the effectiveness of this particular antibiotic may decrease.

Doxycyclin usually appears in capsule form. It is taken orally as prescribed usually with a glass of water. It is advisable that you do not lie down for at least thirty minutes after taking medication because doing so may cause stomach pains. Doxycyclin also reacts badly with magnesium, calcium, and aluminum-based medicines. You must never take it side-by-side those kinds. Make sure that you are full-informed regarding the possible side effects and special precautions that need to be taken upon using Doxycyclin. The best source of information that will guide you through your treatment is none other than your doctor. Check regularly with your doctor for the entirety of your treatment for cases that may affect your health. Continue to take Doxycyclin until the full term of the prescription is reached. On the flip side, never overuse this drug. Stay within the prescribed dosage. If you feel that you need more or less at any given point in your treatment, there is no one better to check it with than your doctor. Like many synthetic drugs, Doxycyclin comes with a handful of side effects that can be manageable or otherwise. Mild results of Doxycyclin intake include nausea, vomiting, stomachaches, head ache, and diarrhea. If any of these effects persists, contact your doctor immediately. Never make an impression that severe effects are normal. Doctors prescribe Doxycyclin despite its known side effects because they know that the benefits are still greater than the drawbacks. If the side effects are getting to a point where it is already threatening your life, then it is obviously a cause for alarm. Another important thing to note is that

Doxycyclin does lessen the effectiveness of certain birth control pills. As this may result to unwanted pregnancy, which could be affected by the strong drug use, you must also get an advice regarding a more reliable birth control option. Keep your Doxycyclin capsules stored at room temperature and away from the reach of young children. Moisture and excessive sunlight may affect its effectiveness so it is best to keep the drug away from their sources as well.
From : Medicalook.com

Antidiuretic Hormone (Vasopressin)

Roughly 60% of the mass of the body is water, and despite wide variation in the amount of water taken in each day, body water content remains incredibly stable. Such precise control of body water and solute concentrations is a function of several hormones acting on both the kidneys and vascular system, but there is no doubt that antidiuretic hormone is a key player in this process. Antidiuretic hormone, also known commonly as arginine vasopressin, is a nine amino acid peptide secreted from the posterior pituitary. Within hypothalamic neurons, the hormone is packaged in secretory vesicles with a carrier protein called neurophysin, and both are released upon hormone secretion

Physiologic Effects of Antidiuretic Hormone
Effects on the Kidney

The single most important effect of antidiuretic hormone is to conserve body water by reducing the loss of water in urine. A diuretic is an agent that increases the rate of urine formation. Injection of small amounts of antidiuretic hormone into a person or animal results in antidiuresis or decreased formation of urine, and the hormone was named for this effect.
Antidiuretic hormone binds to receptors on cells in the collecting ducts of the kidney and promotes reabsorption of water back into the circulation. In the absense of antidiuretic hormone, the collecting ducts are virtually impermiable to water, and it flows out as urine.
Antidiuretic hormone stimulates water reabsorbtion by stimulating insertion of "water channels" or aquaporins into the membranes of kidney tubules. These channels transport solute-free water through tubular cells and back into blood, leading to a decrease in plasma osmolarity and an increase osmolarity of urine.

Effects on the Vascular Syste

In many species, high concentrations of antidiuretic hormone cause widespread constriction of arterioles, which leads to increased arterial pressure. It was for this effect that the name vasopressin was coined. In healthy humans, antidiuretic hormone has minimal pressor effects.

Control of Antidiuretic Hormone Secretion
The most important variable regulating antidiuretic hormone secretion is plasma osmolarity, or the concentration of solutes in blood. Osmolarity is sensed in the hypothalamus by neurons known as an osmoreceptors, and those neurons, in turn, simulate secretion from the neurons that produce antidiuretic hormone. When plasma osmolarity is below a certain threshold, the osmoreceptors are not activated and antidiuretic hormone secretion is suppressed. When osmolarity increases above the threshold, the ever-alert osmoreceptors recognize this a the cue to stimulate the neurons that secrete antidiuretic hormone. As seen the the figure below, antidiuretic hormone concentrations rise steeply and linearly with increasing plasma osmolarity.
Osmotic control of antidiuretic hormone secretion makes perfect sense. Imagine walking across a desert: the sun is beating down and you begin to lose a considerable amount of body water through sweating. Loss of water results in concentration of blood solutes - plasma osmolarity increases. Should you increase urine production in such a situation? Clearly not. Rather, antidiuretic hormone is secreted, allowing almost all the water that would be lost in urine to be reabsorbed and conserved.

There is an interesting parallel between antidiuretic hormone secretion and thirst. Both phenomena appear to be stimulated by hypothalamic osmoreceptors, although probably not the same ones. The osmotic threshold for antidiuretic hormone secretion is considerably lower than for thirst, as if the hypothalamus is saying "Let's not bother him by invoking thirst unless the situation is bad enough that antidiuretic hormone cannot handle it alone."
Secretion of antidiuretic hormone is also simulated by decreases in blood pressure and volume, conditions sensed by stretch receptors in the heart and large arteries. Changes in blood pressure and volume are not nearly as sensitive a stimulator as increased osmolarity, but are nonetheless potent in severe conditions. For example, Loss of 15 or 20% of blood volume by hemorrhage results in massive secretion of antidiuretic hormone. Another potent stimulus of antidiuretic hormone is

nausea and vomiting, both of which are controlled by regions in the brain with links to the hypothalamus.

Disease States
The most common disease of man and animals related to antidiuretic hormone is diabetes insipidus. This condition can arise from either of two situations:
Hypothalamic ("central") diabetes insipidus results from a deficiency in secretion of antidiuretic hormone from the posterior pituitary. Causes of this disease include head trauma, and infections or tumors involving the hypothalamus.

Nephrogenic diabetes insipidus occurs when the kidney is unable to respond to antidiuretic hormone. Most commonly, this results from some type of renal disease, but mutations in the ADH receptor gene or in the gene encoding aquaporin-2 have also been demonstrated in affected humans.

The major sign of either type of diabetes insipidus is excessive urine production. Some human patients produce as much as 16 liters of urine per day! If adequate water is available for consumption, the disease is rarely life-threatening, but withholding water can be very dangerous. Hypothalamic diabetes insipidus can be treated with exogenous antidiuretic hormone

Bacitracin

Chemical data C66H103N17O16S
Mol. mass 1422.69 g/mol
Routes
Topical, intramuscular

Bacitracin is a mixture of related cyclic polypeptides produced by organisms of the licheniformis group of Bacillus subtilis var Tracy. Its unique name derives from the fact that the bacillus producing it was first isolated in 1943 from a knee scrape from a girl named Margaret Tracy. As a toxic and difficult-to-use antibiotic, bacitracin doesn't work well orally. However, it is very effective topically. Its action is on gram positive cell walls.

Bacitracin is synthesised via the so-called

nonribosomal peptide synthetases (NRPSs), which means that ribosomes are not involved in its synthesis.

Mechanism of action
Bacitracin interferes with the dephosphorylation of the C55-isoprenyl pyrophosphate, a molecule which carries the building blocks of the peptidoglycan bacterial cell wall outside of the inner membrane .

Clinical use
Bacitracin is used in human medicine and is "approved by the FDA for use in chickens and turkeys."
As bacitracin zinc salt, and in combination with other topical antibiotics (usually polymyxin B and neomycin), it is used in ointment form for topical treatment of a variety of localized skin and eye infections, as well as for the prevention of wound infections. In the United States a popular brand name Neosporin contains Bacitracin as one of its antibiotic agents along with Neomycin and Polymyxin B. Bacitracin can also be bought in pure form for those with allergies.
It is also commonly used as an aftercare antibiotic on tattoos. It is preferred over Neosporin because of its fewer ingredients, which lowers chances of an allergic reaction.
In infants, it is sometimes administered intramuscularly for the treatment of pneumonias. This formulation is sold under the brand name Baciim®.
From Wikipedia