EHS 202 Pharmacology for EMS - Week 5

EHS 202 Pharmacology for EMS - Week 5 Lecture 1

• Week 5 Lecture 1 covers Drug Regimes and Special Considerations.
• Lecture objectives include discussing common pharmacotherapy problems and alternative treatments.
• Discussing the use of pharmacotherapy as an adjunct to treatment.
• Describing physiological changes across the lifespan, including pregnancy, that may affect drug pharmacokinetics.
• Identifying and discussing variables to consider before administering a drug to a patient.
• Discussing drug transfer across the placenta and effects on the fetus.

Special Considerations

• Medication regimens for specific patient groups require special consideration related to pharmacokinetics and pharmacodynamics.
• Special groups include pregnancy, pediatrics, and the geriatric population.

Drugs During Pregnancy

• When administering medication to a pregnant patient, the paramedic must consider both the mother and fetus.
• Maternal exposure to drugs can result in fetal exposure.
• The effects of the drug affect both the mother during pregnancy & labor, and the child.

Physiological Changes in Pregnancy

• Physiological changes occur throughout pregnancy, affecting pharmacodynamics and pharmacokinetics.
• Cardiovascular system changes include increased cardiac output, heart rate, decreased vascular resistance, an increase in circulating blood volume, and changes in preload and afterload.
• Respiratory system changes include increased respiratory rate, increased metabolic rate and oxygen requirements, and reduction in inspiratory and expiratory reserves, and residual capacity.
• Other systemic changes include increased renal function, hyponatremia, proteinuria, and relative anaemia.

Altered Pharmacokinetics During Pregnancy

• Absorption may be increased or decreased due to factors like delayed gastric emptying and motility, increased ventilation rates, and increased skin surface area.
• Distribution is affected by increased body fat, which increases the volume available for lipid-soluble drugs, and a reduction in serum albumin concentration.
• Metabolism may be either increased or decreased, with hepatic function decreasing and renal function increasing. Caffeine metabolism is reduced while some anticonvulsant metabolism is increased.
• Excretion is affected by increase in maternal renal blood flow and glomerular filtration rate (GFR) during the first 8 months of gestation.

Variation in Teratogenic Susceptibility During Gestation

• The placenta connects the mother to the fetus and allows teratogenic drugs to pass through.
• Timing of exposure is critical, especially during the first trimester (18-55 days gestation), when embryo development is most susceptible.

Maternal Drug Use During Pregnancy

• Some drugs are beneficial for either the mother or the developing fetus (e.g., folic acid).
• Many drugs should be avoided or limited during pregnancy unless the benefit to the mother outweighs the risk to the fetus.
• Drug regimes for maternal conditions should be reduced to minimum therapeutic dose possible.
• Drug effects on the embryo can occur before the mother realizes she is pregnant.

Drugs and Children

• Administering medication to a child can be emotionally and practically challenging, particularly with IV access and cooperation.
• Children’s body composition differs from adults, with higher water content and a higher percentage of body fat, and lower muscle mass.
• Children also show increased metabolic rates.
• Drug regimens for children depend on age, height, weight, or body surface area

Altered Pharmacokinetics in Children

• Children’s pharmacokinetic profiles are different from adults; they are not simply "little adults".
• Drugs can have different, sometimes unintended, effects in children.
• Distribution of drugs is affected by composition differences from adult counterparts.
• Drug dosage or frequency needs adjustments to account for different metabolic and excretion rates.

Altered Physiological Responses to Drugs – Extrapyramidal Reactions

• Extrapyramidal reactions are common with antipsychotic drugs.
• These reactions include dystonia, akathisia, parkinsonism, and tardive dyskinesia.
• Reactions are characterized by various motor and body movements.

Drugs and the Elderly

• Aging leads to various physiological changes that affect drug responses.
• Elderly people are more sensitive to drug effects.
• A high percentage (70-80%) of adverse drug reactions in the elderly are dose-related.
• Elderly people often take multiple medications for various conditions (polypharmacy).
• The variation in pharmacokinetics in this population may lead to a narrow index between effectiveness and toxicity.

Polypharmacy

• Polypharmacy refers to situations where a patient takes multiple medications for various conditions.
• Such situations increase the risk of adverse drug reactions, falls, and hospitalizations in older adults.
• Risks of adverse drug reactions increase with the number of medications.

Altered Pharmacokinetics in the Elderly

• Absorption is reduced in the elderly due to reduced stomach acid, delayed gastric emptying, and decreased blood flow to intestines.
• First-pass metabolism in the liver tends to decrease.
• Distribution changes occur with altered body composition (increased proportion of fat stores), decreased total body water, decreased plasma albumin, and decreased blood flow to tissues.
• Metabolism slows with decreased hepatic blood flow and reduced oxidative activity of the cytochrome P450 system.
• Excretion decreases due to reduced glomerular filtration rate and renal function.

Adjuncts to Pharmacotherapy

• Discusses non-medication approaches for treating medical issues.
• Includes alternatives to medicating patients in emergency treatment.
• Examples are anxiety management, fracture stabilization, burn dressings, splinting, bandaging, and calm approach/reassurance.

Before Treating Patients with Medication

• Factors to consider before prescribing medication.
• Includes what criteria a paramedic should use to make a drug choice.

Drug Indications

• A drug indication defines the condition for which a drug is useful.
• Marketed indications (approved by the relevant regulating body, e.g. therapeutic Goods Administration).
• Approvals may require scientific evidence for effectiveness and appropriate use.

Drug Precautions

• Drug precautions are conditions that prompt advance caution when dealing with a drug.
• The criteria need to be considered to assess the benefits and dangers of the drug in the specific patient.

Drug Contraindications

• A contraindication is a factor that poses an unacceptable risk when administering a drug.
• Relative contra-indications occur when there are potential risks to using the drug that outweigh the identified benefits
• Absolute contraindications occur when use of the drug will result in life-threatening endangerment or detriment.

Where to Get Information on Medication

• Sources of medication information include the drug manufacturer and other sources like MIMS (Monthly Index of Medical Specialties).
• The drug manufacturer must provide details of their drug's indications, contra-indications, pharmacological mechanisms, pharmacokinetic parameters, and potential adverse effects.
• Other sources detail details on the drug for use by the public and health professionals.

Medication Revision

• For next week, review Flumazenil, Naloxone, and Activated Charcoal using the JRCALC and Abu Dhabi Civil Defence formulary and PHECC.

References

• A range of approved sources and references are provided.

Week 5 Lecture 1 focuses on Drug Regimes and Special Considerations in pharmacotherapy. It includes discussions on pharmacokinetics and pharmacodynamics specifically for pregnant, pediatric, and geriatric patients. Learners will understand the factors influencing drug administration and the importance of fetal safety.