Presentation on theme: "Oxford University Hospitals NHS Trust Injectable medicines study day:"— Presentation transcript:
1Oxford University Hospitals NHS Trust Injectable medicines study day: Claire WaghornPharmacist
2Kinetics oral vs IVStability and compatibilityInformation sourcesHigh risk medicines
3Why do we use Injectable medicines? If the oral route is unsuitable e.g. NBMIf medicines are destroyed by stomach acid e.g. insulinIf medicines are not absorbed orally e.g. heparinIf the IM route is inappropriate use IV medicines e.g. haemophiliaProvides flexibility:To obtain high blood concentrations very quicklyFor a rapid, continuous responseFor a slow, continuous infusion, titrated according to responseOther examples eg gentamicin
4Kinetics: oral dose vs. IV bolus Single IV bolus dose profile
5Multiple daily dosing vs. infusions Why would you want to give intermittent infusions eg red man syndrome.Speed shock – if given too quicklyMultiple daily dosing at steady state
6Kinetics: IV bolus + infusion Which drugs would you want to give loading dose?Why?Profile following a loading dose (bolus) and maintenance infusion
7Relationship between plasma level & effect = peakTherapeutic range= troughNarrow therapeutic range – what does it mean?Ask for examples – Theophylline, digoxin, gentamicin.Vancomycin – just do trough levels (see MI bulletin)
8Stability of Injectable products After a medicine has been prepared, it starts to degrade. This results in by-products, which may be pharmacologically active, inactive or even toxic.Incompatible medicines may:Block venous access deviceIntroduce an embolusThese may reduce the effectiveness of treatmentMinimise risks by:Adhere to compatibility informationPrepare immediately before useMaximum expiry 24 hours after preparationPrepare before use – injectables SOPCheck Embolus definition.
9Mechanisms by which medicines degrade pH dependent reactions (acid-alkaline)Photo degradation (light)Concentration dependent precipitationReaction with water (aqueous solutions)Absorption of medicine by components of drug delivery systempH dependent reactions – just some background wouldn’t expect you to work out if compatible.Most drugs are weak acids – mix with fluids ??
10pH Dependent Degradation pH < 7: acidicpH > 7: alkalineAcidic and alkaline medicines or solutions may react with one anotherGlucose 5% = pH 4-5Sodium chloride 0.9% = pH 7Mix like pH with like pH
11pH Sensitive medicines- examples Amphotericin = acidicFungizone brand: glucose 5% 4.2<pH<5.0Use glucose 5% flushesPhenytoin = alkaline always given in sodium chloride 0.9%, precipitation risk if pH<11.5Epoprostenol (Flolan), Sodium fusidate (Fucidin), Terlipressin (Glypressin) all come with buffered solution for preparing these medicines: always use it.Insulin comes buffered in solution of pH 7Phenytoin – needs a filter because of risk of precipitation
12Amphotericin and Terlipressin Use the diluent supplied. Don’t give it away unless it is needed.
13Photo-degradation Light is energy Promotes chemical reactions May result in degradationLight-sensitive medicines: brown ampoule for storageUsual effect is change in colour e.g. dobutamine turns pink.TPN cover bags to protect fat soluble vitaminsSodium Nitroprusside:Degrades to cyanide products on exposure to lightWrap infusion bag and giving set with foil providedBrown ampoules – vitamins, frusemideAminophylline – straw coloured to start with.
14Emulsions Emulsions are very delicate balance of oil and water. Upsetting this balance can cause cracking or splitting.Identified by milky white appearance.PN, diazepam emulsion, fat soluble vitamins, propofol.Why is there a diazemuls product and a diazepam injection???
16Concentration-dependent Precipitation Medicines often poorly soluble in aqueous solutionFormulated as salts to increase solubilityMay require minimum volume of dilutione.g. cotrimoxazole: (75mL glucose 5% or 125ml sodium chloride 0.9% per 5mL ampoule)Precipitation possible at low temp(e.g. mannitol, 20% = supersaturated solution)Calcium salts, magnesium salts, avoid mixing with other medicines, especially phosphatesFormulated in polyethylene glycol???Correcting magnesium and calcium far more these days.
17Adsorption by delivery system Medicines may adsorb onto plastic, glassPVC main problemInsulin, glyceryl trinitrate, ciclosporin, isosorbide dinitrateLeeching of phthalate plasticisers (ciclosporin)Low sorption giving setsNon-PVC bagsShort expiry times in PVC ?Not a problem with insulin as titrating it to response.Phthalates leached with cyclosporin – not a significant problem.
18What can you do to ensure that incompatibilities are avoided? Check if drugs are compatible with the infusion fluid and each other. Unless you have positive proof that they are do not give together.Ideally do not infuse drugs at the same time through the same venous access device.Where several drugs are given through the same device flush well with sodium chloride 0.9% (or glucose 5% if the injectable monograph advises) before, between and after administration to avoid mixing.If any obvious change occurs to a solution DO NOT ADMINISTER IT – ask the pharmacist for advice.
19Information sources Local medicines administration procedures Injectable medicine monographsBNF Appendix 6: intravenous additivesProduct information leaflets (SPC)Clinical Pharmacist on wardMedicines Information department (Ext )Extravasation Antidotes for different drugsPlastic surgery regHydrocortisone inj/creamDiclofenac gel
26High alert medicinesIncreased risk of causing significant patient harm when used in error.Knowing which medicines are high alert – remind you to use additional safety strategies.Injectable examples: amiodarone, chemotherapy, vasoactive agents, heparin, opioids, insulin, opioidsThree ways to safeguard therapy:Reduce or eliminate errors e.g. training, ready to administer solutionMake errors visible e.g. independent double checks, bar codingMinimise consequences of error e.g. monitoring, antidote prescribed and available.Dalteparin LMWHHeaprin now ready to useCardiac monitoring for phenytoin.Monitoring with PCAs
28National Patient Safety Agency Alerts March 2007 Promoting safer use of injectable medicines– competencies re: preparation, administration and monitoring of injectable medicinesMarch 2007 – competence re: preparing and administering Heparin therapy
29Nov 2010 Preventing fatalities from loading doses June 2010 Safer administration of insulinFeb 2010 Injectable medicines in theatresApril 2008 Heparin flushesMarch 2007 Promoting the safer use of injectable medicinesMay 2006 High dose diamorphine and morphineOctober 2002 Potassium solutions: risks to patients from errors occurring during intravenous administration
30High Alert Medicines Potassium Ampoules -Store in CD cupboard Max rate = 10-20mmol / hourMax peripheral concentration = 40mmol / litreCare with mixingAmiodaroneCentral administration if repeated dosesMax concentration for dilutionPhenytoinCardiac monitoringFilter when administering as an infusionWhere are ampoules kept?10 years ago research – lots of problems.Mix thoroughly but generally use ready made solutions.(with or without pump at 20mmols/L)