Clinical Review
Clinical Review Clinical Review identifies issues in
the medical literature of interest to clinicians in Africa. Essential
references are given at the end of each section
Pharmacy Review
Several years ago I wrote about a new method for disin- fecting water using nothing more than sunlight and old plastic bottles. The method has been further developed over the past few years and now an update is needed. The basic method is now called SODIS (solar water dis- infection). A study published in the American Journal of Tropical Medicine and Hygiene1
looked at the effectiveness of
the method in laboratory conditions and in natural sun- light. Two-litre polyethylene terephthalate (PET) bottles of water were contaminated with different pathogens and exposed to natural sunlight and to artificial ultra- violet (UV) light.
Duplicate bottles were used with additives to see if the effectiveness of the method could be improved. Some bottles had added lime juice (equivalent to one lime in each 2litres of water), others had added slurry made from pulping whole limes (about one lime in 2litres) including the rind. Limes were chosen as they are widely available in tropical countries, and because they contain chemicals known as psoralens that disrupt DNA in the presence of UV light. PET plastic allows the correct frequency of UV light to pass through. The results showed that the lime slurry killed all de-
tectable Escherichia coli bacteria (a common contami- nant of water polluted by human faeces) in 30 minutes of sunlight exposure, and killed off nearly all the bacteria in the dark. The lime juice killed off all detect- able bacteria in 2.5 hours in sunlight, and nearly all in 30 minutes. The bottles without the lime juice took 2.5 hours to kill off all the bacteria, and after 30 minutes only half the bacteria were killed.
Another set of bottles were contaminated with MS2 virus; it took 6 hours to kill all measurable viruses with both lime juice and lime slurry, and the bottles con- taining lime slurry were disinfected after 2.5hours in sunlight.
Another set of bottles were contaminated with murine norovirus (norovirus is a common cause of diarrhoea and vomiting), but the SODIS technique was not effective with either lime juice or lime slurry. This is possibly because the virus contains no DNA. SODIS works best in full sunlight, on cloudy days there is not enough UV light to kill bacteria, but as lime slurry was effective even in the dark, it shows that this technique is effective in decontaminating water polluted by bacteria.
July 2012 Another paper on SODIS2 looked at ways of reduc-
ing the cloudiness of water. Suspended clay from soil makes some water cloudy and reduces the effect of UV light. Water needs to be substantially clear in order for sufficient light to pass through and kill bacteria. Sodium chloride (NaCl, common salt) is effective in making some clay settle from the water, leaving it sufficiently clear to be effective. The paper looked at the effect of different concentrations of NaCl on the different types of clay that are commonly found in water. The addition of NaCl at a concentration of 1g/litre
was effective in clearing water containing bentonite (one of the clays studied), but not the other clays. NaCl solutions of this strength taste salty, but are palatable, and not harmful to health. Water containing this much salt is not suitable for making tea, but as water is boiled for tea (or coffee) the method is unnecessary as boiling the water for a few moments is sufficient to kill off all the bacteria. These advances of SODIS show that it can be used in some areas with cloudy water (1g/litre is about the same as half a teaspoon of salt in a 2-litre bottle), and that adding lime pulp reduces the time needed to disin- fect water contaminated by bacteria from 2.5 hours to 30 minutes. Cold water can be made fit to drink without having to boil it and then allowing it to cool I cannot allow 2012 to pass without mentioning the Olympic Games. In the next few months, London and other parts of the UK will see a large increase in the number of people who do not have English as their first language. The Olympic village in London has a medical centre staffed by volunteer medical staff including phar- macists who will be dealing with athletes and visitors from hundreds of different countries and will be faced with the task of labelling medicines in a way that the patients will be able to understand. Poor health literacy – an inability to understand either written or spoken health-related information – is a problem in most countries. Several studies have been done in the USA looking at different methods of making instructions on prescribed medicines easier to under- stand. An early Canadian study3
looked at the effects
of adding simple line drawings to the warning labels of medications (e.g. a cocktail glass crossed out for ‘no alcohol’). The illustrations used made no difference in the understanding of the labels, largely I expect because the drawings were of such poor quality that there were incomprehensible. A recent study4
looked at three different ways of
labelling the basic instructions for taking medicines: standard labelling (e.g. take two tablets twice a day); patient centred labelling (e.g., take two tablets in the morning and two tablets at bedtime); graphic represen- tation of four boxes each representing different times of day (morning, mid-day, evening, night) with the ap- propriate number written in the corresponding box, the blank boxes being blacked out (e.g. 2nn2). The study showed that the graphic representation helped with more complicated dose regimens (e.g., two tablets twice daily), but had no effect on simpler regimens (e.g. one tablet at night). A study using information leaflets for individual
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