This helps to explain why it has freedom from the gastrointestinal side-effects typical of other NSAIDs. A third previously unknown cyclooxygenase pathway is initiated by an enzyme found in the brain and spinal cord. This enzyme is specifically affected by paracetamol and it is this effect that explains its effectiveness in relieving pain and reducing fever without gastrointestinal side-effects. Ibuprofen Ibuprofen is another drug that blocks the enzyme that makes prostaglandins, resulting in lower levels of these in the body.
Ibuprofen is prescribed for mild to moderate pain, caused by many and diverse conditions. The usual dose for minor aches and pains, including painful periods and a high temperature, is to mg every four to six hours. As with other drugs in this class ibuprofen is usually enteric coated and should be taken with or just following food.
The drug does have suspected interactions. If taken with lithium a mood stabilizer it may lead to increased levels of lithium due to its influence on lithium excretion by the kidneys. Ibuprofen has a similar effect on an antibiotic known as gentamycin. Gentamycin levels may rise, thus increasing the risk of side-effects. It should also be avoided during pregnancy as no adequate studies have been completed on its safety during this period.
Side-effects are similar to other drugs in this category, such as rash, abdominal pain, nausea, diarrhoea and heartburn dyspepsia. Renal function is also affected so ibuprofen should be used cautiously in patients who already have a degree of renal impairment or congestive cardiac failure. Paracetamol Paracetamol relieves pain and fever in adults and children and is probably the most widely used medicine in fulfilling this role.
It can be prescribed by a doctor or pharmacist, but generally it is bought as an over the counter medicine. It is over years since the drug was first discovered and 36 Clinical tip The recommended adult dose for paracetamol is mg six hourly, and no more than eight tablets in a hour period. As long as this dose is adhered to, there are no toxic effects. There are no groups of people who should not take paracetamol and interactions with other medicines are rare. Paracetamol is quickly absorbed by the body and its peak serum levels occur within approximately 30 minutes to two hours after ingestion.
Elimination is also rapid: paracetamol has a half life of about two hours. It is vital that the recommended dose be adhered to, because a substantial overdose of paracetamol is likely to result in liver damage and requires immediate treatment.
When paracetamol is broken down by the liver it produces an active byproduct. In order to neutralise this, the liver attaches a substance known as glutathione to it. In overdose, the rate of the byproduct increases far quicker than the liver can manufacture glutathione. Eventually the liver stores are exhausted and the reactive byproduct starts to damage the liver tissue itself. Treatment of overdose requires skilled hospital management.
An antidote called n-acelylcysteine is available and is given intravenously. It is important that the antidote is administered quickly and it is best given within 12 hours of ingestion.
However, it has been shown Chapter 3 that even 48 hours post-ingestion the antidote has beneficial effects. Clinical tip It is worth remembering that paracetamol is often combined with decongestant ingredients in cold and flu remedies.
Therefore, this should be considered by the patient if taking the full dose so that accidental overdose can be avoided. The size of retail packs is also intended to reduce the risk of overdose. Pharmacies are limited to a maximum tablet pack and shops are limited to packs of Therefore, they are given for moderate to severe pain please refer to the World Health Organisation analgesic ladder.
Opioid drugs are a class of natural, synthetic and semi-synthetic agents and are used for their analgesic, anti-tussive stop you coughing and anti-diarrhoeal properties. This class of drug is derived from the opium poppy and its properties have been used for centuries.
Clinical tip You may find a number of terms that are used interchangeably when describing drugs in this category: narcotic, opiate and opioid. All opioids exert their effect through binding with specific receptors called opioid receptors located in the central nervous system brain and spinal cord or peripherally in the gastrointestinal tract.
There are four types of opioid receptor and they are designated by the Greek letters m mu , k kappa , s sigma and d delta. Different opioid analgesics bind in different ways with a variety of Local anaesthetics and analgesics these receptors, so explaining why a range of effects and side-effects can occur. Opioid drugs are agonistic in nature: they mimic our own endorphins, bringing about a similar analgesic reaction. There are numerous opioid analgesic preparations, some natural e.
We will focus on morphine as a strong agonistic drug and codeine as a moderate agonist or weak opioid. Morphine Opioid drugs are thought to work through a number of mechanisms. You will recall that at the beginning of this chapter we discussed the importance of calcium channels opening in order to bring about the transmission of a nerve signal across a synapse.
Morphine is thought to block these channels from opening so that the pain signal breaks down. It is also thought that morphine opens potassium channels in neurones, so making the inside more negative, a condition known as hyperpolarization.
This makes the firing of a pain neurone more difficult. The most important effects of morphine occur on the central nervous system and the gastrointestinal tract and include: Analgesia. This term refers to the loss or relief of pain but without the loss of consciousness.
Morphine is useful in both acute and chronic types of pain. The person is still aware of the pain but does not recognize it as an unpleasant sensation. This in itself is a useful effect as pain often leads to anxiety and agitation. Euphoria tends to be present in patients who are prescribed the drug for acute pain, whereas patients with chronic longstanding pain may lose this effect. This is caused by the respiratory centre in the brain stem becoming less sensitive to the respiratory drive of carbon dioxide.
It is one of the more troublesome side-effects that you need to be aware of, particularly as it can occur with therapeutic doses. It is the commonest cause of death in acute opioid poisoning. Depression of the cough reflex. This does not match the analgesic or respiratory depressive effects of morphine. Therefore, weaker opiates, such as codeine, can be used in anti-tussive preparations. Nausea and vomiting. This occurs in up to 40 per cent of people who are prescribed morphine when they first start to take the drug.
As they become tolerant of the medicine this effect is reduced. Pupillary constriction. The drug stimulates a pair of cranial nerves called the occulomotor nerves which cause this phenomenon. Clinical tip The discovery of pinpoint pupils is still used as a significant diagnostic feature of opiate overdose as other causes of unconsciousness tend to cause the pupils to dilate. Effects on the gastrointestinal tract. Morphine reduces the rate at which the gastrointestinal system moves motility.
This leads to constipation, which is often severe and very troublesome for the patient. All patients receiving morphine should be considered for an aperient. Morphine also affects the smooth muscle of the biliary tract, causing a rise in the pressure within this system. It is due to this effect that morphine should be avoided in people suffering from biliary colic due to gallstones: if morphine is given it might actually increase the pain rather than lessen it.
The 38 general slowing of the gut may affect the absorption of other drugs. Despite its side-effects, morphine is still regarded as the gold standard by which other analgesic medications are measured. Absorption of the drug from the gastrointestinal tract is not particularly good. Significant first pass effect occurs in the liver, and therefore subcutaneous, intramuscular or intravenous injections are usually given. Repeated doses of morphine cause tolerance, resulting in the need to prescribe a higher dose of the drug to achieve the same effect.
Physical and psychological dependence does occur. Codeine This is a less potent analgesic than morphine, and is frequently referred to as a weak opioid.
However, it has an advantage over morphine in that it is well absorbed when taken orally, although when increased to higher doses for severe pain the analgesic effect does not increase above a certain range. Large amounts of the drug do not provide extra analgesia; therefore, it is only suitable for mild to moderate pain.
Codeine has a lower potential for dependency making abuse of the drug less likely, although cases have been reported. The drug has a good anti-tussive quality at doses that do not produce analgesia; therefore, it has the potential for use in cough medicines. However, in most non-prescription cough medicines, it has been replaced by newer drugs such as dextromethorphan, a synthetic narcotic, which has the same anti-tussive properties of codeine. Codeine is used in drugs which are classed as analgesic mixtures.
For example, co-codamol tablets contain codeine phosphate 8mg and paracetamol mg. Another example that you may come across regularly is co-dydramol, which contains dihydrocodeine 10mg and paracetamol mg per tablet.
Opioid antagonists As discussed above, respiratory depression is a side-effect of opiates. Therefore, in opioid overdose, an antidote is necessary. This comes in the form of a drug called Naloxone which has great Chapter 3 attraction to all three opioid receptors. Naloxone blocks the actions of morphine and our own endorphins by occupying the opioid receptors but not bringing about any response, so effectively stopping anything else connecting to the receptor.
Naloxone, therefore, quickly reverses the effects of opioid drugs. Clinical tip The main clinical use of Naloxone is to treat respiratory depression caused by opioid drugs in overdose, whether accidental or intentional.
It is usually given intravenously and its effects are immediate. It has a relatively short half life as it is quickly metabolised by the liver.
Therefore, when treating a patient you may see the drug repeatedly used in order to maintain respiratory function. Local anaesthetics and analgesics Adjuvant drugs Opioid antagonists are used in combination with non-opioid and opioid drugs to facilitate the management of pain in patients, particularly complicated and chronic pain. They can be divided into two broad categories: co-analgesic drugs and drugs that are used to relieve the side-effects of analgesics.
Co-analgesics include drugs such as antidepressants, anticonvulsants, local anaesthetic agents and anxiolytics. Drugs commonly used to treat side-effects include laxatives, antihistamines, neuroleptics and antiemetics. Case studies j Dawn Mason, a year-old woman, has undergone major abdominal surgery. The medical staff have decided to change her analgesia from opioids to non-steroidal anti-inflammatory medication as she is four days post-surgery.
A health care assistant approaches you and asks you to explain the mode of action of the different types of analgesia and why the patient is now stepping down from one set of analgesia to another.
Discuss this with reference to: the mode of action of these two drugs; the importance of stepping down post-operative analgesia; the maintenance required to achieve a steady plasma concentration of analgesic; how you would put this information into terms that the health care assistant will understand. The doctor has prescribed him paracetamol and ibuprofen. The dose he can have for each drug is: ibuprofen, mg every 6—8 hours; paracetamol, mg every 4—6 hours, maximum 2g in 24 hours.
Discuss this with reference to: pharmacodynamics: mode of action of the two drugs; pharmacokinetics: the need for regular dosing to achieve therapeutic plasma concentration; how you would put this information in terms that Alex and his parents will understand. It is a defence mechanism. We can suffer pain without tissue damage.
Pain is a difficult concept to define. At rest the inside of a neurone carries a negative charge. In order for the neurone to fire the inside must become positive. Sodium moves into the neurone to make it positively charged. The pre-synaptic neurone allows calcium to enter. The neurotransmitter allows the post-synaptic neurone to be excited or inhibited. Pain is received by nociceptors. Nociceptors are fired by heat, pressure or chemicals. Nociceptors are non-adapting, high threshold fibres.
Pain is transmitted by A delta and C fibres. A delta and C fibres synapse in the dorsal horn of the spinal cord. The pain impulse is interpreted in a number of areas in the brain. The analgesic system is a descending system. It is thought to close the gate to pain stimuli.
Endorphins, dynorphins, enkephalins are important in modifying pain. There are two classes: esters group and amides. Block sodium channels in the neurone. Usually presented as dilute preparations e. Can cause vasodilation so are often given with adrenaline. Can be given topically, via infiltration, as a nerve block, as an epidural, as a spinal anaesthetic or as an intravenous injection.
Lower body temperature and have anti-inflammatory properties. Block the production of prostaglandins. Block cyclo-oxgenase pathways.
Limit prostaglandin E effects on the nociceptors. Have marked gastrointestinal and renal side-effects. Paracetamol damages the liver if the recommended dose is not followed.
Paracetamol overdose is treated with n-acetylcysteine. Work on receptors in the central nervous system. Some drugs are natural compounds and some are synthetic agents. Block entry of calcium into pre-synaptic neurone. Open potassium channels making it harder for the pain neurone to fire. Their main effects are on the central nervous system and gastrointestinal tract.
Morphine is the gold standard by which other opioids are measured. Morphine can cause tolerance and dependence. Codeine is a weak opioid. Naloxone is given to reverse the effects of morphine. Calculations 1 Pethidine mg in 2ml is available to you. However, the patient has been prescribed 75mg.
How much do you give? The stock you have contains mg in 5ml. How many ml would you give? What is the least number of tablets you can give if the prescription is a dose of 50mg? You have 5mg in 1ml ampoules.
How much would you give? You have available mg in 1ml. How much fluid would you draw up? The patient is prescribed 75mg. How much do you draw up? Tablets are mg. What is the maximum number of tablets you can give in a hour period? You have reconstituted the morphine to make a dose of 10mg in 1ml. You have available 50mg in 1ml. How much do you administer? You have fentanyl 0. How much would you draw up? Cornock, M. Godfrey, H. Mann, E.
Melzack, R. Science — London: NICE. Explain the mode of action of a range of antibiotics used in practice settings. Demonstrate an understanding of what unwanted effects antibiotics have on humans. Discuss drugs that are used to treat tuberculosis. Define what is meant by viral disease. Describe the mode of action and side-effects of antiviral medicines. Identify the three main causes of fungal infection.
Explain how antifungal medicines act. Demonstrate an understanding of the links between the pharmacology of antimicrobial therapies and the care given by the health practitioner. Correctly solve a number of drug calculations with regard to antimicrobial medicines. Introduction Infectious disease is a major cause of death and disability throughout the world. Many microorganisms live either inside or on the outside of the human body. These cause disease only when our resistance is lowered through other diseases or when our natural barriers have been affected by disease or trauma.
Other micro-organisms are present in the external environment and are taken into our bodies through eating and drinking, breathing or on physical contact. Micro-organisms that live in or on our bodies for the most part have a harmless relationship with us and can be beneficial — for example, bacteria in the gastrointestinal system break down foodstuffs allowing us to absorb vitamin K.
Unfortunately, at times of vulnerability these same organisms can cause infection and damage. Many other microorganisms not normally present in the body attempt to invade our tissues causing damage which can be life-threatening.
Any invasion or abnormal growth pattern of micro-organisms which causes our body to defend itself is an infection. An example would be peritonitis — the inflammation of the delicate serous membrane which lines the abdominal and pelvic cavities and covers the organs which lie within. Infectious micro-organisms are categorized into four main groups: bacteria, viruses, protozoa 46 and fungi. Bacteria and fungi are capable of existing independently of their host — i. Some protozoa and certainly viruses need the mechanisms from our cells in order to replicate and grow.
A further category of infectious agent is called a prion. These have been particularly press-worthy as they cause bovine spongioform encephalopathy BSE. This chapter is designed to give you an introduction to some of the medicines used in combating infections caused by micro-organisms.
Drugs used to combat the variety of microorganisms which may cause us harm are referred to as antimicrobials. The chapter is in no way comprehensive and is intended to whet your appetite to read further, so increasing your knowledge.
The chapter covers antibiotic therapy, antiviral therapy, antiprotoza therapy and finally antifungal therapy. We have tried to give examples of common drugs that you may come across in practice rather than concentrate on a range of drugs that you may only encounter rarely. Bacterial infection We are surrounded by bacteria, most of which are harmless.
Having said this, it is probably safe to say that more deaths and disease have been caused by bacteria than any other cause. Bacteria are classified into a number of types based on how they appear through a microscope — Chapter 4 Antimicrobials Interference with the synthesis of essential bacterial cell components e. Some look like rods, and are called bacilli. Some are round in shape and are called cocci. Others have a spiral or corkscrew shape and are known as spirochaetes.
Bacteria are also categorized by whether they take up a stain called gram stain. Bacteria that absorb this stain are termed gram positive, while those that do not are gram negative. The reason for the difference in the uptake of gram stain is a difference in the cell walls of the bacteria. Gram positive bacteria have a simple cell wall whereas the cell wall of gram negative organisms is much more complex. Difficulty in penetrating this complex wall is likely to be why some antibiotics are less effective against gram negative than gram positive bacteria.
Bacteria cells are different from those of humans. Bacteria do not have a nucleus and so are called prokaryotes. Our cells do have a nucleus and are called eukaryotes. This and other differences between bacteria and human cells is important as antibiotics are designed to target these differences, thus destroying the bacteria while leaving our own cells intact. On the very outside of a bacterium is a wall made largely from a sugar called peptidoglycan.
This is unique to prokaryotic cells. Beneath this wall is a plasma membrane very similar to our own and consisting of a sandwich of phospholipids and proteins.
The cell wall and plasma membrane together are called the bacterial envelope. A bacterium contains cytoplasm which carries similar organelles to our own.
However the genetic material is arranged in one long strand that floats around in the cytoplasm. A prokaryotic cell does not have any mitochondria and energy production is carried out in the plasma membrane see Figure 4. Antibiotics are often described as being bactericidal: in other words, they kill bacteria, usually very rapidly. They are also bacteriostatic, which 47 Chapter 4 Antimicrobials means that the antibiotic prevents the growth of an infection but does not eradicate it totally.
The distinction between these two terms is not black and white because in certain conditions a bactericidal antibiotic may only have a bacteriostatic effect and vice versa.
Their effects are somewhat governed by dosage, outside influences and the health of the patient. The side-effects of trimethoprim include nausea, vomiting, certain blood disorders and skin rashes. The drug can also lead to the development of a type of anaemia due to its affects on folate. This is usually counteracted by giving the patient folinic acid. Selective toxicity is the ability of the antimicrobial to harm a pathogen bacteria without harming our own cells.
Therefore, when discussing selective toxicity in terms of an antibiotic health care workers are referring to the range between the dose necessary to inhibit or destroy the bacteria and the dose at which our own cells become harmed. Thus an antibiotic that is far more toxic to the bacteria than our cells is said to have a greater selective toxicity. Peptidoglycan makes up to 50 per cent of the cell wall in bacteria.
In some cells this wall is very thick. However, certain antibiotics stop the bacterial cell from making this substance, thus rendering the cell useless. This is how drugs such as penicillins and cephalosporins work. Interference with folate Folate is a vitamin required by both bacterial and human cells.
Human cells have evolved a mechanism to directly take up folate from the interstitial fluid. Bacteria on the other hand have to make their own folate and cannot absorb it directly from the environment.
A group of antibiotics called sulfonamides exploit this difference between bacterial and mammalian cells. Bacteria need a substance called para-aminobenzoic acid PABA in order to make the folate they need. Sulfonamides fool the bacteria into taking up a substance that looks identical to PABA but cannot be used by the bacteria. In this way, they prevent the cell reproducing and are therefore bacteriostatic in nature.
Trimethoprim This sulfonamide drug is sometimes given as a combination called co-trimoxazole. Trimethoprim is given orally as it is well absorbed by the gastrointestinal system. In this sense, books on pharmacology in anesthesia are essential, since they provide information on this process, and also on the preparation of drugs.
In the pharmaceutical field there is a variety of drugs that if not properly administered can damage the heart, altering its functioning and may cause severe consequences when the situation is not immediately attended to. In view of this situation, it is advisable to consult cardiovascular pharmacology , defined as the specialty that studies the effects of drugs on the circulatory, vascular, nervous and endocrine systems that play an important role in this process.
Likewise, there are ideal medical procedures to treat the pathologies related to these clinical conditions, which are included in the referred texts, where any reader, student or expert will obtain support to reinforce their knowledge in the area. Cardiac Pharmacology author Jassin M.
Jouria Source: NurseCe4Less Cardiovascular Pharmacology author Roger L. Royster, John F. Cardiovascular drugs author Umesh R. Desai Source: Virginia Commonwealth University. At the time of administering a drug, the gestation process represents a condition of care for all women; therefore, correct knowledge is required regarding the properties of the drug, characteristics of the patients, as well as the stages of pregnancy and lactation.
A good guide for acquiring information on this subject is provided by books on pharmacology in obstetrics , which describe all the special considerations that should be taken into account when prescribing medical treatment for pregnant women. The purpose of these texts is to avoid making mistakes in the administration of medication that could have serious consequences for both the mother and the fetus, which would bring misfortune instead of maintaining the happiness for the new creature.
Adams was on the faculty of Lansing Community College and St. Leland Norman Holland, Jr. PhD Norm , over 25 years ago, started out like many scientists, planning for a career in basic science research.
He was quickly drawn to the field of teaching in higher medical education, where he has spent most of his career. Among the areas where he has been particularly effective are preparatory programs in nursing, medicine, dentistry, pharmacy, and allied health.
Holland is both a professor and supporter in nursing education nationwide. Drug interactions may result from either increased or decreased pharmacodynamics. Drug interactions may result from either increased or decreased excretion. What occurs when two drugs compete for the same receptor site, resulting in increased activity of the first drug?
Synergistic effect c. Carcinogenicity d. Displacement ANS: D The displacement of the first drug from receptor sites by a second drug increases the amount of the first drug because more unbound drug is available. An expected response of a drug is the desired action.
A synergistic effect is the effect of two drugs being greater than the effect of each chemical individually or the sum of the individual effects. Carcinogenicity is the ability of a drug to cause cells to mutate and become cancerous. What do drug blood levels indicate? They confirm if the patient is taking a generic form of a drug. They determine if the patient has sufficient body fat to metabolize the drug. They determine if the amount of drug in the body is in a therapeutic range.
ANS: D The amount of drug present may vary over time and the blood level must remain in a therapeutic range in order to obtain the desired result. Generic drugs do not necessarily produce a different drug blood level than proprietary medications.
Body fat is not measured by drug blood levels. Drug blood levels only measure the amount of drug in the body; they do not determine the source of the medication. What is the process by which a drug is transported by circulating body fluids to receptor sites? Osmosis b. Distribution c. Absorption d.
Biotransformation ANS: B Distribution refers to the ways in which drugs are transported by the circulating body fluids to the sites of action receptors , metabolism, and excretion. Osmosis is the process of moving solution across a semipermeable membrane to equalize the dilution on each side.
Absorption is the process by which a drug is transferred from. Biotransformation, also called metabolism, is the process by which the body inactivates drugs.
The nurse assesses which blood level to determine the amount of circulating medication in a patient? Peak b. Trough c. Drug d. Therapeutic ANS: C When a drug is circulating in the blood, a blood sample may be drawn and assayed to determine the amount of drug present; this is known as the drug blood level.
Peak levels are only those drug blood levels that are at their maximum before metabolism starts to decrease the amount of circulating drug. Trough levels are only those drug blood levels that are at their minimum when metabolism has decreased the amount of circulating drug and before an increase caused by a subsequent dose of the medication.
Therapeutic levels are only those within a prescribed range of blood levels determined to bring about effective action of the medication. The nurse administers 50 mg of a drug at AM that has a half-life of 8 hours. What time will it be when 25 mg of the drug has been eliminated from the body? What will the nurse need to determine first in order to mix two drugs in the same syringe?
Absorption rate of the drugs b. Compatibility of the drugs c. Drug blood level of each drug d. Medication adverse effects ANS: B Knowledge of absorption is important but not in order to mix drugs. In order to mix two drugs, compatibility is determined so there is no deterioration when the drugs are mixed in the same syringe. Drug level does not indicate if it is acceptable to mix medications in the same syringe. Adverse effects are important for the nurse to know, but not in order to mix drugs.
A patient developed hives and itching after receiving a drug for the first time. Which instruction by the nurse is accurate? Stop the medication and encourage the patient to wear a medical alert bracelet that explains the allergy. Explain to the patient that these are signs and symptoms of an anaphylactic reaction.
Emphasize to the patient the importance to inform medical personnel that in the future a lower dosage of this drug is necessary. Instruct the patient that it would be safe to take the drug again because this instance was a mild reaction. ANS: A This initial allergic reaction is mild, and the patient is more likely to have an anaphylactic reaction at the next exposure; a medical alert bracelet is necessary to explain the reaction.
Signs and symptoms of an anaphylactic reaction are respiratory distress and cardiovascular collapse. A more severe reaction will occur at the next exposure, and the patient should not receive the drug again. History of liver disease b. Intake of a vegetarian diet c. Sedentary lifestyle d. Teacher as an occupation. ANS: A Liver enzyme systems are the primary site for metabolism of drugs. Intake of a vegetarian diet may affect absorption but not metabolism.
Sedentary lifestyle and occupations could affect metabolism exposure to environmental pollutants , but these do not have the most significant effect on metabolism. The nurse can anticipate that the patient will receive this medication a.
ANS: C The percutaneous route refers to drugs that are absorbed through the skin and mucous membranes. Methods of the percutaneous route include inhalation, sublingual under the tongue , or topical on the skin administration. The parenteral route bypasses the gastrointestinal GI tract by using subcutaneous subcut , intramuscular IM , or intravenous IV injection. In the enteral route, the drug is administered directly into the GI tract by the oral, rectal, or nasogastric route.
A nurse is preparing to administer tetracycline to a patient diagnosed with an infection. Which medication should not be administered with tetracycline? Ativan b. Tylenol c. Colace d.
Mylanta ANS: D Administering tetracycline with Mylanta can provide an antagonistic effect that will result in decreased absorption of the tetracycline. Ativan, Tylenol, and Colace are not contraindicated to administer with tetracycline. Select all that apply. A drug must be dissolved in body fluids before it can be absorbed into body tissues. A solid drug taken orally must disintegrate and dissolve in GI fluids to allow for absorption into the bloodstream for transport to the site of action.
The process of converting the drug into a soluble form can be controlled to a certain degree by the dosage form. Elixirs take longer to be liberated from the dosage form.
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