Pharmacology and Prescribing Module 2

What is an allosteric modulator?

A substance that binds to a receptor and changes the receptor's response to stimuli.

What is a drug?

Any substance other than food that affects living systems.

When is a drug legally considered a medicine?

When it is used therapeutically for administration to humans.

What are excipients?

Non-active ingredients contained in medicines alongside the active drug.

What are the legal medicine categories in order of greatest to least control?

Controlled Drugs

Prescription Medicines

Pharmacist Only Medicines

Pharmacy Medicines

General Sale Medicines.

How can drugs produce their effects?

Most drugs bind to protein targets in the body and initiate a chemical reaction.

What is a therapeutic effect?

The desired effect produced by a medicine.

What is an adverse effect?

An undesirable effect that occurs when a drug affects normal cells or tissues in an unwanted way.

What is the purpose of therapeutic drug use?

To achieve the desired effect with minimum hazard.

What is drug misuse?

Using a drug in a way that significantly increases its potential hazards.

What is drug abuse?

Repeatedly using a drug for purposes other than its intended therapeutic effects.

What does pharmacokinetics describe?

The movement and modification of a medication inside the body: absorption, distribution, metabolism and excretion.

What does pharmacodynamics describe?

How a medication interacts with the body to produce therapeutic and adverse effects.

What are the main factors that can modify renal drug excretion?

Renal function, urine pH and other drugs that compete for active tubular transport.

How can urine pH affect drug excretion?

Some drugs are ionised differently depending on pH, which can alter their excretion.

What is oral bioavailability?

The fraction of an orally administered drug that reaches the systemic circulation.

Why is oral bioavailability less than 100% for many medicines?

Not all of the orally administered dose is absorbed into the blood.

What is the bioavailability of an intravenous drug?

100%, because it is administered directly into the bloodstream.

Why are other injectable medicines not necessarily 100% bioavailable?

They must still be absorbed from their injection site into the systemic circulation.

What are the 4 important pharmacokinetic parameters?

Clearance, volume of distribution, half-life and bioavailability.

What is volume of distribution?

A pharmacokinetic measure describing the apparent distribution of a drug throughout the body.

What happens to half-life when clearance increases?

Half-life decreases.

What is a therapeutic range or therapeutic window?

The range between the minimum effective concentration and the minimum toxic concentration.

What is the minimum effective concentration (MEC)?

The minimum plasma concentration required to produce the desired therapeutic effect.

What is the minimum toxic concentration (MTC)?

The plasma concentration above which toxic effects may occur.

What is the therapeutic index?

A measure of the safety margin between therapeutic and toxic effects.

What does a wide therapeutic index mean?

There is a relatively large difference between the therapeutic and toxic concentrations, making accidental toxicity less likely.

What does a narrow therapeutic index mean?

There is little difference between therapeutic and toxic concentrations, so careful monitoring may be required.

What happens to plasma drug levels after a single dose?

They rise and then fall.

What is a steady state?

The plateau reached when repeated dosing results in relatively stable drug concentrations.

How long does it take to reach steady state with repeated dosing?

Approximately four half-lives.

What is a loading dose?

A dose designed to achieve a desired plasma concentration relatively quickly.

What is the loading dose formula?

V(d) × desired concentration.

Why is understanding pharmacokinetics important for midwives?

It helps maximise beneficial effects, minimise harm and select an appropriate dose, route and dosing frequency.

How can medicines interact pharmacokinetically?

For example, two medicines may be metabolised by the same enzymes and compete for enzyme sites.

How can medicines interact pharmacodynamically?

Two medicines may produce similar effects, increasing the overall response, or one medicine may oppose another.

What is pharmacogenetics?

The combination of pharmacology and genomics to help match medicines and doses to individual genetic profiles.

What is pharmacoepidemiology?

The study of differences in medicine responses between populations.

What is pharmacoeconomics?

The evaluation of the costs and benefits of medicines used in populations.

Why is pharmacodynamics important for midwives?

It helps explain why medicines work, why people respond differently, why side effects occur, how interactions develop and why the lowest effective dose should be used when appropriate.

What are the main drug targets?

Receptors, enzymes, ion channels and transporters.

What happens when a drug binds to a receptor?

It can activate, modify or block a physiological response.

What is the lock-and-key model?

A model where the receptor is the lock and the ligand is the key; the ligand must have the appropriate shape and chemical properties to bind.

How does an agonist interact with a receptor?

It binds to and activates the receptor, producing a response.

What is an example of an agonist?

Oxytocin acts as an agonist at oxytocin receptors to stimulate uterine contractions.

How does a partial agonist differ from a full agonist?

A partial agonist activates a receptor but produces a smaller response than a full agonist.

How does an antagonist interact with a receptor?

It binds to the receptor without activating it and prevents another ligand from producing its response.

What is an example of an antagonist?

Naloxone acts as an antagonist at opioid receptors and reverses opioid effects.

What is the difference between affinity and efficacy?

Affinity is how strongly a drug binds to its target, while efficacy is the ability of the drug to produce a response once bound.

What is the difference between potency and efficacy?

Potency relates to how much drug is required to produce an effect, while efficacy relates to the maximum effect the drug can produce.

What is receptor upregulation?

An increase in the number of receptors, making cells more responsive to a drug or natural ligand.

What happens to oxytocin receptors during pregnancy?

Their number increases as pregnancy progresses, making the uterus increasingly responsive to oxytocin.

Why is oxytocin receptor upregulation important in midwifery?

It helps explain increasing uterine responsiveness to oxytocin during labour and the use of synthetic oxytocin for induction or augmentation.

What are transporters?

Proteins that move substances across cell membranes.

How can transporters affect medicines in pregnancy?

Placental transport systems influence movement of drugs between maternal and fetal circulations.

How can transporters affect medicines during breastfeeding?

Some drugs enter breast milk through passive diffusion while others may be actively transported by proteins.

How can medicines act on enzymes?

Many medicines work by inhibiting enzymes and reducing the production of substances involved in disease processes.

What are ion channels?

Proteins that control the movement of ions such as sodium, potassium and calcium into and out of cells.

Why are ion channels important drug targets?

They play important roles in nerve conduction, muscle contraction and cardiac function.

How can pregnancy affect medicines acting on ion channels?

Physiological cardiovascular changes during pregnancy can influence responses to drugs acting on calcium, potassium and sodium channels.

How do antacids work?

They neutralise gastric acid through a direct chemical reaction.

How do osmotic laxatives work?

They draw water into the bowel through osmosis, softening stool and promoting bowel movements.

What is the placental barrier?

An interface between maternal and fetal circulation, allowing exchange of oxygen, nutrients and waste while also allowing many drugs to cross.

Does the placenta completely protect the fetus from medicines?

No. It is selective rather than completely protective, and drugs can cross it.

What factors influence whether a drug crosses the placenta?

Molecular size, lipid solubility, protein binding and degree of ionisation.

Why is placental drug transfer important to midwifery?

Medicines taken during pregnancy can reach the fetus and potentially affect fetal development or physiology.

Why is pharmacokinetics particularly important during pregnancy?

Pregnancy changes ADME.

Increased plasma volume

Increased cardiac output

Increased renal blood flow

Increased GFR

Reduced albumin

Altered liver enzymes

Meaning medicine responses and safety may differ from the general population.

Why is pharmacology important during breastfeeding?

Medicines may pass into breast milk and potentially affect the breastfeeding infant.

What should a midwife consider when a woman uses herbal remedies alongside prescribed medicines?

The herbal remedy may alter pharmacokinetics or pharmacodynamics and may change the safety or effectiveness of the prescribed medicine.

What is the ideal goal of pharmacotherapy?

To achieve the desired therapeutic effect while minimising harm.

What is the purpose of selecting an appropriate dose, route and dosing schedule?

To achieve drug concentrations high enough for the desired effect while avoiding concentrations that cause adverse effects.

What is a drug interaction?

When one medicine or substance changes the effect, concentration, metabolism or action of another medicine.

What is a contraindication?

A situation or condition in which a medicine should not be used because it may cause harm.

What is a precaution?

A circumstance where extra care, assessment or monitoring is needed when using a medicine.

What is the role of laboratory tests in medicine management?

They can help assess clinical status, monitor medicine effects and support safe treatment decisions.

Why are clinical trials important?

They establish the safety and effectiveness of treatments, including medicines.

Why are pregnant and breastfeeding people underrepresented in clinical trials?

Ethical and safety concerns around research involving pregnancy and breastfeeding.

Why does underrepresentation of pregnant people in trials matter?

Most evidence may come from the general population even though physiological changes in pregnancy can affect ADME and medicine responses.

Why does the WHO support ethical inclusion of pregnant and breastfeeding people in research?

To improve the quality of evidence and support equitable care.

What is ON TRACK in Aotearoa?

A network supporting maternal and perinatal research towards stronger evidence for effective care.

What does Medsafe do in relation to clinical trials?

It regulates medicines and oversees clinical trials, including ensuring research is ethical, robust and prioritises participant safety.

What happens during Phase I-II clinical trials?

Basic safety, dosage and initial efficacy are established in a relatively small group.

What happens during Phase III clinical trials?

Large-scale trials confirm effectiveness compared with existing therapies and monitor side effects.

What happens during Phase IV clinical trials?

Post-marketing surveillance tracks longer-term safety.

Why are medicines required to undergo strict regulation before use?

To demonstrate quality, safety, efficacy and appropriate manufacturing standards.

What does therapeutics mean?

The application of evidence-based practice to treatment decisions as part of a treatment plan.

What does pharmaceuticals mean?

The study and use of drugs to prevent, diagnose and treat disease.

What must new medicines demonstrate before use?

Quality, safety, efficacy and that they meet manufacturing standards.

What is the role of PHARMAC in medicine access?

Assesses evidence about effectiveness, health benefits and impact on the health system and makes decisions about funding and access.

Why is health literacy relevant to medicine access?

People need to understand how to take medicines safely and effectively.

Why can rural location affect access to medicines?

Geographical barriers may make accessing healthcare providers, prescriptions and medicines more difficult.

Why is cultural safety relevant to medicine access?

Culturally unsafe healthcare can create barriers to accessing and engaging with appropriate treatment.

Why is it important for a midwife to understand medicine funding and access systems?

These systems influence whether wāhine and whānau can obtain medicines and may contribute to inequities in access to treatment.

Where can a midwife find information about medicine safety during pregnancy?

Resources such as the New Zealand Formulary, Medsafe information, Healthify, clinical guidelines and other approved medicines information resources.

Where can a midwife find information about medicines and breastfeeding?

LactMed, the Drugs and Lactation Database.

What is the overall purpose of pharmacology knowledge in midwifery?

To support safe, evidence-informed prescribing and administration by understanding how medicines work, how the body handles medicines, potential risks and interactions, and how pregnancy and lactation can affect medicine safety.

List four receptor types?

Ligand-gated ion channels

GPCR

Kinase-linked receptor

Intracellular receptor

List three functions of CARM?

Collect ADR reports

Monitor medicine safety

Identify medication safety concerns