Erythromycin is an antibiotic used for the treatment of a number of bacterial infections. This includes respiratory tract infections, skin infections, chlamydia infections, pelvic inflammatory disease, syphilis, it may be used during pregnancy to prevent Group B streptococcal infection in the newborn, as well as to improve delayed stomach emptying. It can be given intravenously and by mouth. An eye ointment is recommended after delivery to prevent eye infections in the newborn. Common side effects include abdominal cramps and diarrhea. More serious side effects may include Clostridium difficile colitis, liver problems, prolonged QT, allergic reactions, it is safe in those who are allergic to penicillin. Erythromycin appears to be safe to use during pregnancy. While regarded as safe during breastfeeding, its use by the mother during the first two weeks of life may increase the risk of pyloric stenosis in the baby; this risk applies if taken directly by the baby during this age. It is in the macrolide family of works by decreasing bacterial protein production.

Erythromycin was first isolated in 1952 from the bacteria Saccharopolyspora erythraea. It is on the World Health Organization's List of Essential Medicines, the safest and most effective medicines needed in a health system; the World Health Organization classifies it as critically important for human medicine. It is available as a generic medication and is not expensive; the wholesale price in the developing world is between 0.06 USD per tablet. The cost to the United Kingdom's NHS is 0.18 GBP per tablet. In 2016, it was the 281st most prescribed medication in the United States, with more than a million prescriptions. Erythromycin can be used to treat bacteria responsible for causing infections of the skin and upper respiratory tract, including Streptococcus, Staphylococcus and Corynebacterium genera; the following represents MIC susceptibility data for a few medically significant bacteria: Haemophilus influenzae: 0.015 to 256 μg/ml Staphylococcus aureus: 0.023 to 1024 μg/ml Streptococcus pyogenes: 0.004 to 256 μg/ml Corynebacterium minutissimum: 0.015 to 64 μg/mlIt may be useful in treating gastroparesis due to this promotility effect.

It has been shown to improve feeding intolerances in those. Intravenous erythromycin may be used in endoscopy to help clear stomach contents. Erythromycin is available in enteric-coated tablets, slow-release capsules, oral suspensions, ophthalmic solutions, gels, enteric-coated capsules, non enteric-coated tablets, non enteric-coated capsules, injections; the following erythromycin combinations are available for oral dosage: erythromycin base erythromycin estolate, contraindicated during pregnancy erythromycin ethylsuccinate erythromycin stearate For injection, the available combinations are: erythromycin gluceptate erythromycin lactobionateFor ophthalmic use: erythromycin base Gastrointestinal disturbances, such as diarrhea, abdominal pain, vomiting, are common because erythromycin is a motilin agonist. Because of this, erythromycin tends not to be prescribed as a first-line drug. More serious side effects include arrhythmia with prolonged QT intervals, including torsades de pointes, reversible deafness.

Allergic reactions range from urticaria to anaphylaxis. Cholestasis, Stevens–Johnson syndrome, toxic epidermal necrolysis are some other rare side effects that may occur. Studies have shown evidence both for and against the association of pyloric stenosis and exposure to erythromycin prenatally and postnatally. Exposure to erythromycin has been linked to an increased probability of pyloric stenosis in young infants. Erythromycin used for feeding intolerance in young infants has not been associated with hypertrophic pyloric stenosis. Erythromycin estolate has been associated with reversible hepatotoxicity in pregnant women in the form of elevated serum glutamic-oxaloacetic transaminase and is not recommended during pregnancy; some evidence suggests similar hepatotoxicity in other populations. It can affect the central nervous system, causing psychotic reactions and night sweats. Erythromycin is metabolized by enzymes of the cytochrome P450 system, in particular, by isozymes of the CYP3A superfamily.

The activity of the CYP3A enzymes can be induced or inhibited by certain drugs, which can cause it to affect the metabolism of many different drugs, including erythromycin. If other CYP3A substrates — drugs that are broken down by CYP3A — such as simvastatin, lovastatin, or atorvastatin —are taken concomitantly with erythromycin, levels of the substrates increase causing adverse effects. A noted drug interaction involves erythromycin and simvastatin, resulting in increased simvastatin levels and the potential for rhabdomyolysis. Another group of CYP3A4 substrates are drugs used for migraine such as ergotamine and dihydroergotamine. Earlier case reports on sudden death prompted a study on a large cohort that confirmed a link between erythromycin, ventricular tachycardia, sudden cardiac death in patients taking drugs that prolong the metabolism of erythromycin by interfering with CYP3A4. Hence, erythromycin should not be administered to people using these drugs, or drugs that prolong the QT interval.

Other examples include terfenadine, cisapride (Propulsid, withdrawn in many countrie

Diving hazards

Diving hazards are the agents or situations that pose a threat to the underwater diver or their equipment. Divers operate in an environment, they face special physical and health risks when they go underwater or use high pressure breathing gas. The consequences of diving incidents range from annoying to fatal, the result depends on the equipment, skill and fitness of the diver and diving team; the hazards include the aquatic environment, the use of breathing equipment in an underwater environment, exposure to a pressurised environment and pressure changes pressure changes during descent and ascent, breathing gases at high ambient pressure. Diving equipment other than breathing apparatus is reliable, but has been known to fail, loss of buoyancy control or thermal protection can be a major burden which may lead to more serious problems. There are hazards of the specific diving environment, hazards related to access to and egress from the water, which vary from place to place, may vary with time.

Hazards inherent in the diver include pre-existing physiological and psychological conditions and the personal behaviour and competence of the individual. For those pursuing other activities while diving, there are additional hazards of task loading, of the dive task and of special equipment associated with the task; the presence of a combination of several hazards is common in diving, the effect is increased risk to the diver where the occurrence of an incident due to one hazard triggers other hazards with a resulting cascade of incidents. Many diving fatalities are the result of a cascade of incidents overwhelming the diver, who should be able to manage any single reasonably foreseeable incident. Although there are many dangers involved in diving, divers can decrease the risks through proper procedures and appropriate equipment; the requisite skills are acquired by training and education, honed by practice. Entry level recreational diving certification programmes highlight diving physiology, safe diving practices, diving hazards, but do not provide the diver with sufficient practice to become adept.

Professional diver training provides more practice, but continued experience and practice of essential skills is necessary to develop reliable response to contingencies. Divers must avoid injuries caused by changes in pressure; the weight of the water column above the diver causes an increase in pressure in proportion to depth, in the same way that the weight of the column of atmospheric air above the surface causes a pressure of 101.3 kPa at sea level. This variation of pressure with depth will cause compressible materials and gas filled spaces to tend to change volume, which can cause the surrounding material or tissues to be stressed, with the risk of injury if the stress gets too high. Pressure injuries are called barotrauma and can be quite painful potentially fatal – in severe cases causing a ruptured lung, eardrum or damage to the sinuses. To avoid barotrauma, the diver equalises the pressure in all air spaces with the surrounding water pressure when changing depth; the middle ear and sinus are equalised using one or more of several techniques, referred to as clearing the ears.

The scuba mask is equalised during descent by periodically exhaling through the nose. During ascent it will automatically equalise by leaking excess air round the edges. A helmet or full face mask will automatically equalise as any pressure differential will either vent through the exhaust valve or open the demand valve and release air into the low-pressure space. If a drysuit is worn, it must be equalised by inflation and deflation, much like a buoyancy compensator. Most dry suits are fitted with an auto-dump valve, which, if set and kept at the high point of the diver by good trim skills, will automatically release gas as it expands and retain a constant volume during ascent. During descent the dry suit must be inflated manually; the prolonged exposure to breathing gases at high partial pressure will result in increased amounts of non-metabolic gases nitrogen and/or helium, dissolving in the bloodstream as it passes through the alveolar capillaries, thence carried to the other tissues of the body, where they will accumulate until saturated.

This saturation process has little immediate effect on the diver. However, when the pressure is reduced during ascent, the amount of dissolved inert gas that can be held in stable solution in the tissues is reduced; this effect is described by Henry's Law. As a consequence of the reducing partial pressure of inert gases in the lungs during ascent, the dissolved gas will be diffused back from the bloodstream to the gas in the lungs and exhaled; the reduced gas concentration in the blood has a similar effect when it passes through tissues carrying a higher concentration, that gas will diffuse back into the bloodsteam, reducing the loading of the tissues. As long as this process is gradual, the tissue gas loading in the diver will reduce by diffusion and perfusion until it re-stabilises at the current saturation pressure; the problem arises when the pressure is reduced more than the gas can be removed by this mechanism, the level of supersaturation rises sufficiently to become unstable. At this point, bubbles may form and grow in the tissues, may cause damage either by distending the tissue locally, or blocking small blood vessels, shutting off blood supply to the downstream side, resulting in hypoxia of those tissues.

This effect is called decompression sickness or'the bends', must be avoided by reducing the pressure on th

Blanquilla Island

Blanquilla is an island, one of the federal dependencies of Venezuela, located in the southeastern Caribbean Sea about 293 km northeast of Caracas. It is a popular location for divers, as well as famous for its white sand beaches, for which it is named; the island's wildlife include iguanas, as well as wild donkeys and goats. Its reefs are notable for their black coral, used for jewelry and other crafts; the island is formed by the Aves Ridge, a seafloor feature which protrudes above water to the north, forming several other islands. Has an area of 64.53 km²In 2014, assertions made by the Hong Kong media that Venezuela was considering transferring ownership of Blanquilla island to China in exchange for the forgiveness of its $50 billion in debt were denied by the Chinese government. Federal Dependencies of Venezuela List of marine molluscs of Venezuela List of Poriferans of Venezuela