EHS 202 Pharmacology for EMS Week 5 Lecture 1 Drug Dosing Regimes 22_23 PDF

EHS 202 Pharmacology for EMS Week 5 Lecture 1: Drug Regimes and Special Consideration Objectives of this lecture: 1.Discuss common problems associated with pharmacotherapy and outline alternative treatments; 2.Describe the use of pharmacotherapy as an adjunct to treatment strategies...

EHS 202 Pharmacology for EMS Week 5 Lecture 1: Drug Regimes and Special Consideration Objectives of this lecture: 1.Discuss common problems associated with pharmacotherapy and outline alternative treatments; 2.Describe the use of pharmacotherapy as an adjunct to treatment strategies 3.Describe the physiological changes across the lifespan including pregnancy that may affect drug pharmacokinetics. 4.Identify and discuss the variables to consider prior to administration of a drug to a patient. 5.Discuss the transfer of drugs across the placenta as well as the effects of drugs on the foetus. 2 Special Considerations Medication regimes across specific patient groups require special consideration in relation to pharmacokinetics and pharmacodynamics. Special groups including pregnancy, pediatrics and the geriatric population. 3 Drugs During Pregnancy 4  We need to consider several aspects: When administering medication to a pregnant patient the paramedic must consider the care of two patients, the mother and fetus. Maternal exposure can result in fetal exposure. The effects of the drug during pregnancy & labour for the mother and the child. 5 Physiological Changes in Pregnancy From conception and throughout pregnancy there are a number of physiological changes which occur, many of which can alter the process of pharmacodynamics & pharmacokinetics. Physiological changes including: Cardiovascular System: Increased cardiac output and heart rate Decreased vascular resistance & reduced blood pressure Increase in circulating blood volume by around 50% Decreased preload and afterload Respiratory System: Increased respiratory rate Metabolic rate & oxygen requirements increases by around 20% Inspiratory & expiratory reserves & residual capacity reduced Hormone related respiratory alkalosis Other Systemic Changes: Increased renal function Hyponatremia and proteinuria 6 Relative anaemia  Altered Pharmacokinetics During Pregnancy: Absorption - May be increased or decreased from the GIT by delayed gastric emptying and motility. Drug absorption from the lungs may be increased due to increased ventilation rates. Drug absorption from the skin may be increased due to increased skin surface area. Distribution – An increase in body fat provides a larger volume for lipid soluble drugs. An increase in body fat reduces albumin concentration in the blood. A reduction in serum albumin affects distribution and plasma levels. 7 Altered Pharmacokinetics During Pregnancy: Metabolism - Hepatic function decreases and renal function increases. Hepatic enzyme activity can be either increased or decreased (metabolism of caffeine is reduced whilst metabolism of some anticonvulsants are increased). Excretion - Maternal renal blood flow and Glomerular Filtration Rate (GFR) increase during the first 8 months of gestation. 8 The placenta is the connection between mother and the fetus. Teratogenic drugs can pass through the placenta affecting the developing fetus. Variation in teratogenic susceptibility during gestation. Timing of the exposure is particularly important with the critical period for embryo development in the first trimester (18-55 days gestation). 9  Maternal drug use during pregnancy. Some drugs are beneficial to either the mother and/or developing fetus for example folic acid. Many drugs should be avoided or limited during pregnancy except where the benefit to the mother is considered greater than the risk to the foetus (antiepileptic, antipsychotic, antihypertensive and diabetes medication). If a drug regime for a maternal condition is required during pregnancy, the number of medications should be reduced if possible and that dose titrated to the lowest possible therapeutic dose. The effects of drug use on the embryo may occur before a woman is aware that she is pregnant (possibly associated with drug interactions). 10 Drugs and Children 11 Challenges Emotionally challenging when dealing with a sick child Administration challenges including IV access and cooperation Changes in body composition – water approximately 80% reducing to around 60% in adults Infants have higher percentage of body fat and lower muscle mass Increased metabolic rate Drug regimes in children are based on age, height, weight or body surface area 12 Changes in pharmacokinetics in children: In terms of drug administration and pharmacokinetics, children aren’t little adults. Drugs may cause a different (sometimes undesired) response when administered to a child compared to an adult (aspirin). Children and infants in particular have altered distribution of drugs compared to adults due to changes in body composition (less fat). Drugs dosage or frequency has to be adjustments to allow different rates of metabolism and excretion. 13 Altered Physiological Responses to Drugs – Extrapyramidal Reactions Extrapyramidal reactions are relatively common following the administration of some antipsychotic drugs (centrally acting dopamine antagonists). Dystonia – spasms, trismus, oculogyric crisis, laryngospasm and opisthotonus (severe hyperextension and spasticity where the head, neck and spinal column enter a bridging or arching position). Akathisia – feeling of motor restlessness (restless leg syndrome) that may look like agitation. Parkinsonism – tremor, rigidity or bradykinesia. Tardive dyskinesia – involuntary movements of the face, mouth or tongue and sometimes of the head, neck, trunk or limbs. 14 Drugs and the Elderly 15 Potential for drug interactions in the elderly Ageing persons undergo a variety of physiological changes that may increase their sensitivity to drugs and adverse drug reactions. It has been estimated that 70-80% of all adverse drug reactions in the elderly are dose related. Often the elderly take multiple medications for multiple conditions including those prescribed by various clinicians and any non- prescribed or over the counter medications self-administered. Due to wide ranging variations in the pharmacokinetic changes in the elderly there is often a narrow index between effectiveness and toxicity. 16 Polypharmacy Polypharmacy refers to any patient taking two or more medications for the treatment of multiple conditions. With an increase in medications and altered physiology in the elderly, there is an increased risk of adverse and serious drug reactions. Adverse drug reactions are a major cause of avoidable falls and preventable hospitalization in the elderly. As the number of medications increase, so does the risk of adverse reactions. 17 Altered pharmacokinetics in the elderly: Absorption Reduction in stomach acid Altered gastric emptying and intestinal blood flow Decrease in first-pass metabolism in the liver Distribution Altered body composition (increased proportion of fat stores) Decrease in total body water Decrease in plasma albumin Decrease in blood flow and cardiac output Metabolism Decrease in hepatic blood flow Decrease in oxidative metabolism (cytochrome P450 system) Excretion Decrease in glomerular filtration rate and renal function 18 Adjuncts to Pharmacotherapy 19 Adjuncts to treatment Do we always need to reach for the reach for drugs to solve our medical or trauma emergencies? What else can we do as clinicians? 20  Anxiety management Fracture stabilization Burns dressings Splinting Bandaging Calm approach/reassurance 21 Before treating our patients with a medication, what things do need to consider? 22 What is a drug indication? ‘An presentation, illness or disorder for which a drug has a documented specific usefulness’. Furthermore, drug indications are: ‘Marketed indications that have been approved by the Therapeutic Goods Administration or an indication for which there is appropriate scientific evidence and/or broad clinical consensus to support their use.’ 23 What is a drug precaution? ‘Clinical caution practiced in advance of administering a drug’. Furthermore: A precaution indicates that there is a possibility of an adverse outcome as a result of drug administration or procedure. Forethought should be used to determine the potential negative outcomes and then whether the benefit of administration is outweighed by the risk (short or long term) to the patient. 24 What is a drug contraindication? ‘A factor that makes dangerous or undesirable the administration of a drug or the performance of an act or procedure in the care of a specific patient’. Contraindications can be further divided into relative contraindications and absolute contraindications. 1. A relative contraindication means that caution should be used when two drugs or procedures are used together (it is acceptable if the benefits outweigh the risks) i.e.. Intramuscular injection prior to thrombolysis. 2. An absolute contraindication means that the drug could result in a life-threatening situation and should not be used under any circumstances 25 Where can we check get more information about a medication ? 26 The drug manufacturer The drug company is required to provide important information about the drug including: Approved name(s) Pharmacodynamic effects Mechanism of action Pharmacokinetic parameters Clinical indications Contraindications and precautions Significant drug interactions 27  The drug manufacturer Drug companies are required to supply a significant amount of information about their drug for both the general public and health professionals. Drug companies tend to be extremely cautious about the approved clinical use and possible adverse effects of their drugs. Information about a drug from a drug company should always be read critically. 28 MIMS – Monthly Index of Medical Specialties 29  MIMS Both the full and abbreviated product information is available including images of the actual medication. 30 Other sources of Information: Drug Formulary of organization where you work. 31 Medication Revision For next week’s quiz, study the following medications using JRCALC, Abu Dhabi Civil Defence formulary & PHECC. Flumazenil Naloxone Activated Charcoal 32  References 1. Guy J (2020). Pharmacology for the Prehospital Professional, Second Edition. Jones & Bartlett Learning. 2. ‘Pharmacology for Health Professionals’, 2nd Edition. (Bryant & Knights) 3. ‘Fundamentals of Pharmacology’, 5th Edition. (Bullock et al.) 4. ‘Prescribing medicines in pregnancy’, 4th Edition. (Australian drug evaluation committee & TGA) 5. ‘Medications in pregnancy and lactation’ parts 1 &2. (Buhimschi & Weiner, 2009). 6. ‘Adverse drug reactions: definitions, diagnosis and management’. (Edwards & Aronson, 2000) 33