Week 3 - Common Medicines

Define polypharmacy

The concurrent use of multiple medications

List the 9 overall categories of common medicines

• Analgesics

• Anti-inflammatories

• Anti-histamines

• GI medications

• Antibiotics

• Anaesthetics

• Sedative-hypnotics

• IV fluid therapies

• Vaccines

Explain analgesics

Medications formulated for pain relief

Name the 2 types of analgesics and give an example of each

• Non-opioids - paracetamol

• Opioids - morphine

Explain the mechanism of action of non-opioids

Modulates the COX-3 enzyme to reduce the production of pain signalling molecules.

Explain the mechanism of action of opioids

An μ-opioid receptor (type of g-protein coupled receptor) agonist, activating g-proteins which blocks the transmission of painful stimuli.

Explain the side effects of non-opioids and opioids

• Non-opioids - safe unless overdose

• Opioids - drowsiness, respiratory depression, constipation

List the 2 types of anti-inflammatory medications and give an example of each

• Non-steroids (NSAIDS) - ibuprofen

• Corticosteroids - prednisone

Explain the mechanism of action of NSAIDS

Inhibit COX-1 and COX-2 enzymes, blocking prostaglandin production to reduce inflammation

Explain the mechanism of action of corticosteroids

Glucocorticoid receptor agonists (type of intracellular receptor), which enhances the transcription of anti-inflammatory mediators, reducing the transcription of inflammatory proteins.

Explain the side effects of NSAIDS and corticosteroids

• NSAIDS - bleeding risk

• Corticosteroids - immunosuppression, fluid retention

Explain how corticosteroids can alter image appearance

Fluid retention can increase lymph node size and alter anatomy

List the 2 types of anti-histamines

• Sedatimg

• Non-sedating

Give the suffix for anti-histamines

-ine

Explain the mechanism of action of all anti-histamines

H₁ receptor (G-protein coupled receptor) antagonist, blocking histamine from binding to reduce allergic symptoms.

Explain the difference between sedating and non-sedating anti-histamines

• Sedating - 1st generation anti-histamines which are non-polar and lipid soluble, therefore can penetrate BBB and result in drowsiness

• Non-sedating - 2nd generation anti-histamines which are polar, ionised and water-soluble, therefore cannot penetrate the BBB and has minimal CNS effects

List the 3 types of GI medications

• Antiemetics

• Acid suppression medications

• Bowl regulation medications

Explain the mechanism of action of antiemetics

Primarily antagonists for cell surface receptors, blocking transmission of nausea-related signals

Give a side effect specific to antiemetics

Drowsiness

Explain the 3 mechanisms of action of acid suppression medications

• Proton pump inhibitors - block the last step of acid secretion

• Anti-histamine antagonists - block H₂ receptors to reduce acid production

• Physicochemical agents - neutralise acids and form a protective barrier by lining the stomach

Give side effects specific to acid suppression medications

• Changes in digestion

• Changes to food tolerance

Explain the 2 mechanisms of action of bowel regulation medications

• Phyiscochemical agents - alter water levels in the bowel

• Opioids agonists - bind to receptors to slow down transit time through the the bowel, preventing diarrhoea

List the side effects for all GI medications

• GI upset

• Altered bowel habits

• Constipation

Explain how GI medications can affect imaging

The presence of excess gas and stool in the bowel can alter the anatomy of the GI tract

Define antibiotics

Medications that disrupt essential functioning of bacteria

List the 4 most common mechanisms of action of antibiotics

• Decreased cell-wall synthesis

• Decreased protein production

• Decreased DNA replication

• Decreased metabolism

Name the most common antibiotic

Penicillin

List side effects of antibiotics

• GI upset

• Altered bowel habits

• Headaches

• Fatigue

Define antimicrobial resistance

Major health threat in which bacteria have become resistant to antibiotic treatment due to the overuse and misuse of antibiotics in healthcare.

Define anaesthetics

Medications that reduce nerve transmission for the purpose of sensation loss

List the 3 types of anaesthetic medications

• Local

• Regional

• General

Explain mechanism of action of local and regional anaesthetics

Blocks voltage-gated sodium channels to reduce neural transmission.

Explain the difference between local and regional anaesthetics

They have the same mechanism of action however local is for numbing a specific area, whereas regional is for numbing major nerve bundles.

Name the routes of administration for local and regional anaesthetics

• Local - topical creams or injections

• Regional - injections

State the suffix for local and regional anaesthetics

-caine

Explain the mechanism of action for general anaesthetics

Drug acts on multiple CNS targets to prevent excitatory neurotransmission and enhance inhibition

Name the 2 routes of administration for general anaesthesia

• IV

• Inhalation

List the 3 types of sedative/hypnotic medications

• Benzodiazepines

• Non-benzodiazepines

• Barbiturates

Explain the mechanism of action of all sedative medications

Modulators that bind to the allosteric site on GABA-A receptors, enhancing the activity of GABA, therefore increasing the amount of Cl^- within neurons to inhibit neural transmission.

Explain the difference in mechanism of action for each sedative medication

• Benzodiazepines - increase the frequency of Cl^- channel opening

• Non-benzodiazepines - selectively bind to only the a1 subunit to increase the frequency of Cl^- channel opening

• Barbiturates - increase the duration of Cl^- channel opening in the absence of GABA

State what letter non-benzodiazepines typically start with

Z

Explain the risks of barbiturates

High risk of dependency and toxicity

Explain the difference between general anaesthesia and sedation

• Sedation - patients are relaxed or in a light sleep and can breathe independently

• General Anaesthesia - patients are unconscious and require breathing support

List the 5 IV fluid therapies

1. Isotonic crystalloids

2. Dextrose-containing fluids

3. Electrolyte replacement solutions

4. Flushes

5. Hydrations fluids

Explain isotonic crystalloids

Water-based solution that contains dissolved salts that replicate the osmolarity of blood plasma

Explain dextrose containing fluids

Water-based solution that contains dextrose (completely dissolved glucose) to provide energy.

Explain electrolyte replacement solutions

Water-based solution that contains a high concentration of a specific ion to be corrected.

Explain flushes

Small volume of a water-based solution containing dissolved ions with the purpose of clearing, checking or maintaing the patience of an IV line

Explain hydration fluids

Water-based solution containing dissolved salts that are given in large volumes to maintain hydration or support kidney function.

Explain the purpose of a vaccine

To expose the body to a safe form of antigen in order to produce an immune response with memory that allows for a faster and stronger response on re-exposure.

Explain inactivated vaccines

Contains dead pathogens

Explain live-attenuated vaccines

Contains a weakened pathogen

Explain mRNA vaccines

Contains mRNA that causes antigen production

Explain viral-vector vaccines

A carrier virus that causes antigen production

Explain protein/subunit vaccines

Contains a component of a pathogen

Explain how some vaccines can affect imaging

Can alter lymph node size and appearance due to immune system activation

Explain how drowsiness and decreased cognition as a side effect of a drug is relevant to medical radiation practice

This can effect a patients ability to understand as well as their decision-making skills, questioning informed consent procedures and their patients ability to listen to instructions.