MODULE 1: BASIC DRUG KNOWLEDGE 1.1 How Drugs Work A drug is a medicine or substance (but not food or water) which when ingested (or otherwise introduced into the body) alters the way the body works physically or mentally. Drugs are either legal or illegal. Some legal drugs can be bought from a shop or pharmacy but many can only be obtained if a doctor prescribes them. ACTIVITY 1 Circle which of the following you think are drugs: HEROIN ASPIRIN ALCOHOL CHOCOLATE MORPHINE CAFFEINE Most medicines come as oral preparations (i.e. they are swallowed). However, some medicines are topical (applied to the skin), external (not swallowed e.g. eye drops, creams, nasal sprays, ear drops), inhaled or injected. A drug only has an effect when it is absorbed into the body. Most medicines are taken orally as tablets, capsules or liquids. After swallowing, the pill or capsule is broken up in the stomach and gut and then the drug is absorbed through the lining of the gut into the blood stream. Once in the blood stream, the drug is carried to where it will have its effect. However, the body sees the drug as a foreign substance. The kidneys and/or the liver will eliminate it from the body in the urine or faeces. This explains why drugs need to be given regularly to keep having an effect. This also explains why people with kidney or liver problems may need to have doses of medicines adjusted. 5
ACTIVITY 2 Explain how each of the following situations will change the effectiveness of a drug. Situation How will the effectiveness of the drug be changed? A particular medicine always causes someone to vomit within 5 minutes of taking it A person s kidneys are damaged (they have kidney failure) A drug is prescribed to be taken daily but the person only takes it twice a week 1.2 Drug Effects and Side-Effects Legal medicines have had to undergo clinical trials to check that the effect they have is real and to find out the range of doses that are effective but also safe. Hoever, all drugs have the potential to cause problems as well as solve them. The effect a drug has will determine what it is used for. For Example, a drug that lowers the blood pressure will be given to people who have blood pressure that is too high. Side-effects are other effects that are not actually needed or wanted. Some side effects will happen in nearly everyone; some will occur very rarely. Some people will be willing to put up with a particular side effect; some people will not. Some side-effects are mild or may disappear once someone gets used to the drug. Some side-effects can cause a lot of discomfort and occasionally, some can actually be life threatening. 6
ACTIVITY 3 A person is prescribed a drug called metformin to treat their diabetes (high blood sugar). The drug successfully reduces the person s blood sugar. However, they feel bloated and complain of feeling sick. What effect is the metformin having? What side-effect is the metformin having? 1.3 Drug Doses How much of a drug a person takes is very important. Too little and it will not have enough of an effect. Too much and the drug will cause more harm than good. In very severe cases, the drug can prove to be toxic and the person may die or be left disabled. From drug trails, the manufacturer will have discovered the minimum dose that will have the desired effect and the maximum dose that can be taken outhout harm being caused. Doctors will take into account a person s age, how well they are and some other factors in order to decide what dose of a drug to prescribe a patient. The BNF (British National Formulary) is a book available to all doctors that will provide them with much of the information they need to prescribe safely and effectively. 7
ACTIVITY 4 A doctor prescribes a medicine for a service-user with a dose of 10-30ml every night. What is the minimum dose that you could give this service-user? What is the maximum dose that you could give this service-user? The person found that 30ml was helping but they still had some symptoms. They ask you to give them 40ml. What would you do? 1.4 How Often to Give a Drug How often a drug needs to be given (i.e. once, twice, three or four times a day) depends on how long the drug works for when it is given. So, if a drug only lasts for 8 hours then the doctor will need to prescribe it to be taken every 8 hours (i.e. three times a day) if he/she wants it to have a 24 hour effect. The doctor will write this information on the prescription and the pharmacist will type this onto the drug label. Most people find it easier if they only need to remember to take a medicine once a day. Sometimes, drugs that only last for 6-8 hours as a normal tablet may be made into a special tablet which gradually releases the drug over a longer period of time. If you see any of the following in a label or box of medicine you know it is one of these specially formulated medicines: Shorthand SR XL MR Full Name Sustained Release Extra Long Modified Release It is very important that SR, XL, or MR tablets or capsules are never broken/crushed/chewed. Doing so will mean the drug will no longer be released gradually as planned and could harm the person taking it. 8
Some medicines have special coatings around them to make them taste better; or to ensure they do not irritate the throat; or stomach or to ensure they are passed into the intestine to be abosrbed. These tablets will be noted as being enteric-coated (EC) or film-coated. Again, it is very important that these tablets or capsules are never broken/crushed/chewed. 1.5 When to Give a Drug Some drugs need to be talen at specific times of the day in order to maximise their effect or to minimise side effects. Drugs that have a side-effect of drowsiness are often best given at night. If a medicine only needs to be taken once daily then it is usually taken in the morning. However, for most once daily drugs it does not actually matter what time of day they are taken as long as they are taken at the same time every day. Some medicines are best given before food (so they are absorbed better), some need to be taken with or after food (to minimise irritation to the stomach) and with some it does not matter when take them in relation to food. If it is important, the label will tell you whether a drug must be taken before or after food. ACTIVITY 5 Circle whether the following statements are true or false. Statement All medicines are given just once a day When you see the intials MR after a drug name, this means the drug must be given in the morning All tablets should be given after food XL, SR, MR and EC tablets must never be broken/crushed/chewed The label on the machine will tell you how often a drug needs to be given 1.6 Medicine Information As a care worker, you cannot be expected to know every detail about every available medicine. However, understanding how the medicine helps the service-user will actually allow you to care for them in a more informed way. Some service-users will not be able to tell you why they take each medicine. This means you may need to use other information sources. Some of these sources are listed on the next page: 9
Information Source Patient Information Leaflets (PILs) GP Pharmacist Nurse BNF (British National Formulary) Internet Colleagues Comments These are found in every original pack of medicine dispensed. They contain information on the dose, common side-effects and practical administration information. As the prescriber, the GP can tell you what the drug is for and how long it is to be given etc. The GP must be made aware of any problems a service-user is having with a medicine. It is the GP (or another prescriber) who must authorise any changes. Pharmacists can be provide you with any information relating to medicines. Some pharmacies are open in the evening and at weekends. A pharmacist can provide general information on a medicine even if it is not for a patient they know. Nurses have a lot of practical experience in administering medicines. If you are struggling with a particular medicine then nurses can often provide you with some helpful tips. A book that contains details of doses, side-effects and other clinical information for all the licensed medication in use in the UK. Some of the medical terminology can be hard to understand. www.medicines.org.uk contains all the available PILs. Internet not always available when working and need to be sure the site you access is reliable and UK based. You should not rely just on the knowledge of other care workers - they may be wrong. If in doubt about any issue, contact a suitable healthcare professional. 10