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22nd February 2010, Monday
Long–acting beta agonist (LABA) drugs should not be used alone in asthma (both children and adults). Package inserts for the two single-agent LABAs approved for asthma, salmeterol and formoterol, will be changed to require that the drugs always be used in combination with an asthma controller medication such as an inhaled corticosteroid.
2. The agents should be used for the shortest time possible to achieve symptom control. Once patients are no longer experiencing symptoms, LABAs should be discontinued if possible with patients maintained on controller medications alone.
3. No label changes for arformoterol, approved only for COPD.
4. The label changes also won't apply to LABAs used for intermittent exercise-induced bronchospasm.
Thus far, the risks associated with LABAs have been seen only in asthma patients. Those risks include severe exacerbations of asthma symptoms, leading to hospitalizations for adults as well as children. Some of these exacerbations have been fatal. The FDA cited data from a placebo-controlled trial called SMART in which salmeterol was associated with excess deaths at an overall rate of 8 per 10,000 patients (95% CI 3 to 13). A meta-analysis of some 60,000 patients in multiple trials of salmeterol and formoterol found that the drugs were associated with a composite of hospitalizations, intubations, and deaths at an excess rate of 28 per 10,000 patients (95% CI 11 to 45). These events were markedly more frequent in adolescents (58 per 10,000) and children (148 per 10,000).
Dr KK Aggarwal
Question of the day
Diarrhea usually results from malabsorption, secretory states and inflammation. Steatorrhea is suggested by pale, smelly stools which would indicate either a small bowel problem or pancreatic insufficiency. In lactose intolerance, the diarrhea tends to be watery. These two are examples of small bowel diarrhea, and for differentiating between them, the causes needs to be known since the diarrheal patterns are different. It is very important to take a good history as watery diarrhea also occurs in colonic diseases like collagenous colitis, which should be typically thought of in an older patient who is using nonsteroidal anti-inflammatory drugs (NSAIDs) and presents with watery, nonbloody diarrhea. Patient history, examination findings and investigations all play a major part in diagnosing diarrhea. A bloody diarrhea, points to colitis and cramping abdominal pain with diarrhea and vomiting points to a small bowel pathology such as Crohn’s disease.
eMedinewS Try this it Works
Dr Good Dr Bad
Formulae in Critical Care
Stroke index (SI)
Milestones in Neurology
Mistakes in Clinical Practice
"U" and "IU" – The "U" can easily be mistaken as the number "0", articularly when the "U" is written too closely after the number. This can lead to tenfold overdoses. And "IU" can be mistaken for "IV" or the number "10". So instead of using "U" and "IU", use the terms "unit" and "international unit".
Eye care snippets by Dr. Narendra Kumar (OptometryToday@gmail.com)
Lens materials and coatings
Lenses are made of either glass or plastic. Glasses used for lenses are ophthalmic crown, photochromatic crown, barium, or flint. Plastics used for lenses are CR–39 or polycarbonate. Besides these standard materials, high index lenses are available both in glass and in plastic. Also available are polarizing lenses.
Optical glass: Modern optical glass was developed in the 19th century by Faraday and Schott. Clear crown glass used for ophthalmic lenses is made of 70% sand, 12% lime, 15% soda, and small amounts of potassium, borax, antimony, and arsenic. Flint glass contains lead oxide to increase refractive index. Flint is softer than crown (but is heavier with increased dispersion and specific gravity). Barium glass contains barium oxide and is similar to flint (with less dispersion). Flint and barium are both used in fused bifocals. Glass is fragile, brittle and breaks into sharp splinters. Heat–toughened lenses are usually made from spectacle crown glass (having refractive index of 1.523). For toughening, the cut lens is placed into a furnace and heated at 6370 C for 50–300 seconds. After heating, it is rapidly cooled. For chemical toughening, the pre–heated lens is lowered into a potassium nitrate solution at 4400 C for 16 hours, which results in a thin but tough compression coating.
Optical plastics: Ophthalmic lenses made of plastic are fast catching up in India. Plastic is lighter, can be moulded into aspheric shapes, fogs less in high humidity, and can be treated to absorb 100% ultraviolet (UV) rays. Made of resin, plastic lenses weigh about 50% less than glass. CR–39 lenses (developed in 1947) have good impact resistance, but their scratch resistance is not as good as that of glass. Refractive index of CR39 (Columbia resin 39) is 1.498. These lenses can be tinted and bleached. Their edges are thicker than glass lens edges. If too thin, these lenses may warp and create astigmatic effects. Scratch–resistance of these lenses can be improved with the help of anti–scratch coatings. Fresnel lenses and prisms are made of 1mm thin vinyl film. But plastic lenses, having relatively low refractive index, are thicker than equivalent glass powers, and once finished these lenses cannot be resurfaced. Plastic bifocals and progressive addition lenses (PALs) are available in various styles. Polycarbonate lenses are more impact resistant, lighter and thinner than comparable CR–39. But these require special handling in processing and surface–coating.
High index lenses: Baseline ophthalmic lens materials are (mineral) crown glass having refractive index 1.523, and (organic) CR39 having refractive index 1.498. High index lenses are made with the incorporation of lead or barium compounds, resulting in increased weight. Schott (in early 1970s) used titanium oxide for raising the index. These lenses are thinner than glass and more so than plastic lenses. Internationally, high index spectacle lenses enjoy a sizeable share as these allow ‘minus’ prescriptions in thinner and more cosmetically appealing lens forms. Further, because of the saving in lens mass, there is substantial weight saving even though higher refractive index glasses have higher specific gravity. All this leads to wearer comfort. The Corning France "Handbook of Ophthalmic Glasses" cites an 8% weight saving at –6.00D using 1.6 index instead of crown glass, and a 14% weight saving at –15.00D using 1.8 index glass.
While glass lenses of refractive index 1.6 are fast becoming the first choice for prescriptions as low as –2.00D in major European countries, the real benefit of reduced thickness and reduced weight is for prescriptions of –6.00D and beyond, for the Indian market in view of the higher cost factor. 1.7 refractive index is available in both glass and plastic materials. 1.8 refractive index, available in glass material only, offers impressive benefits for the high minus power wearer (–15.00D or above), but this patient group is small. Photochromic lenses are available in 1.6 index glass and 1.7 index plastic materials.
Since high refractive index materials have varying degrees of transverse chromatic aberration (visual blurring on oblique gaze), there is need for the application of anti–reflection (AR) coatings, especially for 1.7 or 1.8 index lenses to mask this drawback and to increase optical performance. In organic lenses, broad–band coatings provide additional advantage of improving scratch resistance. Due allowance is to be given while surfacing high index material lens blanks (plastic as well as glass) using tools meant for standard index materials. Tinting high index organic material presents a problem, but AR coating presents no problem.
Tints: Tints, or shades or colours, absorb part of the light entering the glass or plastic lens. Tints may be visible in the form of a colour of the entire lens material or invisible in the form of an extra coating.
On entering the lens, part of the light is transmitted (goes through it), and part of it is absorbed or reflected (not transmitted); 80% transmission of light through a lens means that the material is lighter in tint than a material allowing 20% transmission through it. And 80% absorption of light though a lens means that the material is darker in tint than a material absorbing 20% of light. Usual tints available in the market are Alpha or A1 (light yellow), A2 (light blue), B1 (light bluish–black), B2 (dark bluish-black), SP2, Calobar (green), SP4, Grey, and SP10.
In coloured lens blanks, the tint is permanent and increases in darkness as the thickness of the lens increases. By means of vacuum coating, cosmetically appealing, single gradient tints can be applied to a glass lens. The darker tint at the top helps reduce glare from overhead, and the lighter shade at the bottom permits easy reading. Double gradient tints are darker in shade both at the bottom and top of the lens, with a clear zone in the middle. A uniform bluish colour can also be applied by coating on the back surface of a lens. Colours can be applied to a plastic lens as well. These colours can also be removed by means of bleaching. Bleached lenses can again be coloured when desired. Usually a colour sample chart is kept by the optical dispenser for the patient to choose from.
It is important to suggest a larger frame for sunglasses for wider coverage and sun protection. Also to be remembered is that the frame should be of appropriate size according to face (neither too big nor too small) when it is to be used for prescription sunglasses especially for high powered lenses. Since the eye lens is removed at the time of cataract surgery, aphakic patients need UV protection. They should be advised brown, green, or grey coloured lenses. Constant use of sunglasses may create light sensitivity, and patients may become habitual to their use. Constant use, is, therefore, not advisable. Clear glasses may be advised for indoor use. Polaroid is not a tint. Available in grey, brown, and green, it helps absorb glare such as road and water reflections. (to be continued next week ...)
Lab Test (Dr Navin Dang)
Treat the patient and not the lab reports. Always corelate with clinicl findings.
1-7 April Prostate Disease Awareness Week: Prostate SMS of the day (Dr Anil Goyal)
The prostate produces secretions that form part of ejaculated semen and help in motility of sperms.
11th March World Kidney Day ( Dr N P Singh)
Reducing risk of developing kidney diseases : Keep regular control of blood sugar level
Kidney Terms (Dr G M Singh)
Inflammation of bladder. Definition of acute cystitis includes dysuria, urgency and/or frequency with only 102CFU/ml in mid–stream specimen.
List of Approved drug from 1.01.2009 to 31.10.2009
Sodium metasilicate is NOW available in India as ZENIMMUNE Range of Products.
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