Medicines Optimisation - Year 4

Diagnosis - Opioids

• Coma

• Miosis (small pupils)

• Reduced respiratory rate

• Hypoxia

Diagnosis - Stimulants (ecstasy, cocaine, amphetamine)

• Agitation

• Delirium

• Mydriasis (large pupils)

• Hypertension

• Hyperthermia

• Tachycardia

Diagnosis - Anticholinergics (hyoscine, promethazine, mirtazapine, TCA)

• Drowsiness

• Confusion

• Mydriasis (large pupils)

• Tachycardia

• Urinary retention

Diagnosis - Salicylates

• Nausea/vomiting

• Tinnitus

• Deafness

• Hyperpyrexia

• Hyperventilation

• Metabolic acidosis

Management of poisoned patients

• Symptomatic and supportive care

• Reducing absorption

• Enhancing elimination

• Specific antidotes

7 Ways to reduce absorption of a drug

• Gastric Lavage - potential benefit within 1 hour of ingestion

• Single dose activated charcoal - can absorb drugs if given within 1 hour of ingestion

• Whole bowl irrigation - 2 litres per hour orally until bowl effluent is clear

• Multiple dose activated charcoal - Binds to drug to maintain low concentration of free drug

• Urine alkalinisation - Enhances salicylate clearance by favouring ionisation

• Extracorporeal Elimination - haemodialysis - poisoning complicated by renal failure.

• Chelating agents - calcium is removed and replaced by lead.

Acetylcysteine

Antidote for paracetamol poisoning

Naloxone

Opiate antagonist antidote

Flumazenil

GABA receptor antagonist for benzodiazepine poisoning

Fomepizole

Toxic alcohol poisoning

8 hour rule for paracetamol overdose

• Provided the patient is treated within 8 hours of ingestion, they are unlikely to experience significant liver damage

• Antidote treatment after 8 hours does not guarantee protection

Diagnosis of CKD

• eGFR < 60mL/min/1.73m2 on at least two sperate occasions within 90 days

• Markers of kidney damage (ACR >3mg/mmol)

Either of the following must be present for a minimum of 3 months

Risk factors of CKD

• Hypertension

• Diabetes

• AKI

• Cardiovascular disease

• Structural renal disease or reoccurring kidney stones, or prostatic hypertrophy

• Multisystem disease eg lupus

• Gout

• Family history

• Incidental haematuria or proteinuria

What do you need to do if no diagnosis of CKD but has ongoing risk factors

• Serum creatine

• eGFR

• ACR

• Urine dipstick

Need to be checked annually

Allopurinol

Often used to treat gout so can indicate CKD

What should you change amlodipine to in someone with CKD

ACE inhibitor as is reno protective

Symptoms of CKD

• Fatigue

• Shortness of breath

• Nausea

• Palpitations

• Itch

• Cramps

• Heartburn

• Restless legs

• Frothy urine

• Reduced urine output

Clinical implications of CKD

• Impaired homeostatic function → Metabolic acidosis (treat with sodium bicarbonate), fluid overload (diuretics, dialysis, fluid restrictions), hyperkalaemia (sodium zirconium)

• Impaired endocrine function - anaemia, renal bone disease, hypertension

• Impaired filtration and excretion

Renal bone disease

• Initially asymptomatic

• Body compensates until CrCl < 25ml/min

• Calciphylaxis - deposits of PO and Ca around the body

Management of renal bone disease

• High phosphate diet - dietary restrictions, calcium-based binders are first line → calcium acetate

• Supressing parathyroid hormone release - PO binders may be sufficient, if insufficient add alfacalcidol

Adjustments are made in 4-12 week intervals to allow for time to respond

ONE OF THE MAIN COMPLICATIONS WHEN KIDNEY FUNCTION IS BAD

Renal Anaemia

• Kidneys are the main site of erythropoietin (EPO) production - EPO promotes RBC formation

• In CKD, EPO levels do not increase in response to falling PO2 and anaemia

TREATMENT - Ferritin > 200microg/L. Correct vitamin B12 and folate levels. Start on Erythropoiesis simulating agent (ESA). When someone has an infection ESA less effective

Aim for a Hb of 100-120g/L

ONE OF THE MAIN COMPLICATIONS WHEN KIDNEY FUNCTION IS BAD

Renal bone disease markers

• Vitamin D (low)

• Vitamin B12

• PTH

Anaemia markers

• Ferritin

• Hb

• FBC

Risk factors of AKI

• CKD

• HF

• Liver disease

• Diabetes

• Nephrotoxic drugs

• 65+

• Hypervolemia

• Oliguria

• Neurological or cognitive impairment

Signs and symptoms of AKI

• Regulation of acid/base balance → Acidosis

• Regulation of fluid balance → Oedema, reduced urine output

• Regulation of electrolytes → Hyperkalaemia, cardiac arrhythmias, muscle weakness

• Filtration and excretion → Toxicity of medications with narrow therapeutic window.

Nephrotoxic drugs which can contribute to AKI

• NSAIDS

• ACEI

• ARB

• Metformin

• Potassium sparing drugs - spironolactone

Prevention of AKI in hospital setting

• ACEI/ARBS discontinued on day of administration of bowl preparations and consider withholding for 72 hours.

• Diuretics - discontinue day of administration of oral bowl preparation and withhold for 24 hours

• Withhold ACEI/ARBS pre operatively

• Monitor fluid balance to ensure hydration

Recognising people at risk of AKI in community

• Conditions leading to dehydration - vomiting and diahorrea

• People using nephrotoxic drugs when already at risk of AKI

Observed changes following response to surgery

• Decreased haemoglobin

• Altered respiratory rate

• Altered electrolytes

• Reduced GI mobility

• Inflammatory response

• AKI

What happens to PD medication prior surgery

Parkinsons medication MUST be continued

Examples: Levodopa (co-beneldopa, co-carbedopa), pramipexole

What happens to anti epileptic drugs pre surgery

MUST be continued

• sodium valproate

• Lamotrigine

• Carbamazepine

• Topiramate

• Levetiracetam

What other drugs should you continue during surgery

• beta blockers

• digoxin

• anti- arrhythmias eg - amiodarone

• Steroids - prednisolone

• Statins

What happens to contraceptive pills prior surgery

Stop 4-6 weeks prior major surgery

Risk factors associated with surgical site infection

• Male

• Smoker

• Increased BMI

• Diabetes

• Low albumin and HB

• Open surgical approach

• Blood transfusion

• Blood loss

• Use of drains

• ASA below 2

• Long duration of surgery

5 factors associated with choice of antibiotic surgery

1) Type of surgery

• Clean → no prophylaxis

• Clean contaminated → One dose

• Contaminated → 5-7 days treatment

2) Prophylaxis vs treatment

3) Local resistance

4) Cost

5) Pharmacokinetics

Anti-coagulation considerations prior surgery

• Warfarin - stop 5 days prior

• DOACs (apixaban) - stop timeframe dependent on renal function

• Clopidogrel - 5-7 days pre surgery stop

• Aspirin - Continue less than or equal to 150mg

What do you use to treat post op nausea and vomiting

Cyclizine and ondansetron

Post op pain management

WHO ladder reversed - patients need sufficient pain control to mobilise and aid recovery

Protein binding in paediatrics

Less albumin so higher percentage of free drug

GFR in paediatrics

GFR is LOWER in paediatrics than adults, especially in the first week of life. Elimination by tubular secretion is also reduced

Medications to avoid in children

• Tetracyclines → Effects calcium and so bones and teeth

• Codeine → Respiratory depression

• Aspirin → Reyes syndrome

• Metoclopramide → Dystonic side effects

• Domperidone → Cardiac issues - not effective

Mesolimbic pathway

Reward pathway which includes Ventral tegmental area and nucleus accumbent

Opiates pharmacology

Opioids act at the u-opioid receptor on GABAergic neurons causing disinhibition of dopamine neurones in VTA

Ethanol pharmacology

Acts directly on the dopamine neurones in VTA decreasing after hyperpolarisation (by blocking K+ channel), leading to increased firing rate

Nicotine pharmacology

Acts on nicotine acetylcholine receptors on the dopamine neurones in VTA increasing the firing rate

THC pharmacology

THC acts on the cannabinoid receptor on GABAergic neurones - these are inhibitory, so when you activate them you reduce the amount of GABA released increasing the firing of the action potential.

Why are nicotine patches not addictive

Slow delivery of a drug isn’t rewarding and so isn’t addictive, whereas fast release is

Alcohol and tolerance

Alcohol reverses opioid tolerance so a normal dose of opioids can become fatal with alcohol - it does this by reversal of u-opioid receptor desensitisation (become more sensitive to opioids)

Withdrawal treatments with alcohol

Sudden stopping of alcohol can be lethal → seizures and psychotic episodes

Treat alcohol withdrawals with -

• Benzodiazepines - anxiety

• Anti-epileptics

• Anti-psychotics

Withdrawal treatment for opioids

Stopping opioids quickly is not lethal it just isn’t enjoyable.

Treat with-

• Clonidine (sedative)

• Benzodiazepines (anxiety)

• Sedation

• Replacement therapy - methadone or buprenorphine

How does replacement therapy for opioids work

With replacement therapy you are still activating the opioid receptors, but you dont go into physical withdrawal and you dont gain the euphoric effects.

Varenicline

Nicotine replacement therapy

Partial agonist against nicotinic receptors - stops physical withdrawal. It stops nicotine binding to the receptor so the euphoric effects of smoking are minimised.

Disulfiram

Used to treat alcoholics

Ethanol → Acetaldehyde → Acetic acid

Ethanol → acetaldehyde requires alcohol dehydrogenase

Acetaldehyde → acetic acid requires acetaldehyde dehydrogenase

Disulfiram blocks acetaldehyde dehydrogenase so that you get a build up of acetaldehyde - this makes people feel horrible so they stop drinking

Problem is people can just stop taking this medication

Opioid antagonists

• Naloxone

• Buprenorphine

• Naltrexone

3 main reasons humans relapse

• Taking a small dose of the drug

• Stress

• Being presented with a queue associated with taking the drug

Two factors which contribute to low baseline mood

• Dysregulation of stress hormone

• Increased production of dynorphin

Antalarmin and mifepristone

Treatment of stress hormones:

• CRH-1 receptor antagonist (antalarmin)

• Glucocorticoid receptor antagonist (Mifepristone)

If you could reduce stress you could reduce relapse.

Harm reduction

Aims to allow people to continue to do things but makes things safer whilst they still happen.

Opioid Substitution Therapy Principles

Replace illicit short half life drugs with legally prescribed long half life drugs.

Two drugs currently licensed for OST

• Methadone → activated mu receptor, antagonist of NMDA receptors

• Buprenorphine → Partial agonist mainly at the mu receptor at adequate doses, also a kappa receptor antagonist

Evidence about OST

• Adequate doses of methadone and buprenorphine retain people in treatment well.

• OST has a >85% chance of reducing overall mortality rate amongst opioid users.

• Higher doses are better at keeping people in treatment and reducing illicit drug use.

• Criminal activity decreases for people on OST

Heightened risks of death situations

• Polysubstance use - eg alcohols, benzodiazepines, other CNS depressants

• First 2 weeks of methadone titration

• Post detox from methadone and buprenorphine

• First two weeks after release from prison

• First two weeks after discharge from prolonged hospital stay

Maintenance doses of methadone and buprenorphine

• Methadone 60-120mg

• Buprenorphine 12-16mg - may need up to 32mg

• Methadone doses above 100mg require ECG due to QTc prolongation

• Patients on treatment of <60mg of methadone are twice as likely to leave treatment than those on 60-80mg

Reducing barriers to starting OST

• Optimal daily doses

• Flexibility of take home doses

• High quality medical and psychological services

Monitoring during OST prescribing

• Liver tests for buprenorphine, especially if HCV positive

• ECG - methadone >100mg

• Self reported alcohol and drug use

• Well being

• General health improvements - eg - weight

• Mental health

• Social functioning

Symptomatic relief when patients are detoxing

• Mebeverine

• Ibuprofen

• Prochlorperazine

• Diazepam

• Z-drugs

Effects of having lower D2 receptors

Lower D2 receptors can predispose you to being a user of illicit drugs.

For example people who had more D2 receptors, when they had methylphenidate (ADHD medication) they found the side effects outweighed the benefits, whereas people with lower D2 levels found that the effects of methylphenidate were pleasurable.

D2 receptors

D2 receptors → encode euphoria

Single nucleotide polymorphisms (SNP)

Reduces the expression of a receptor - so if you have an SNP in your DNA for D2 receptor then you will make fewer D2 receptors than someone who doesnt have an SNP - studies show SNP is a risk factor for drug abuse.

Bupropion

Dopamine/ noradrenaline re-uptake inhibitors - aims to increase activation of D2 receptors - if you do this you get reward in your life and don’t seek reward by elicit drugs

4 Types of stem cells

Totipotent → Can differentiate into any type of cell

Pluripotent → Can differentiate into any cell within an adult organism

Multipotent → Limited potential - different stem cells in a particular tissue

Unipotent → Can differentiate into one type of cell

Analysis techniques to detect cell markers on stem cells

• Western blotting

• RT-PCR

• Immunochemistry

• Flow cytometry

Ways to enrich cell populations

• Centrifugation

• MACs

• Flow cytometry

Flow cytometry

Most powerful way of detecting specific molecules within a cell.

Can be used for sorting/ isolating different populations of cells

Powerful analytical technique

Power of flow cytometry is the use of fluorescent antibodies against particular antigen on the cell surface

Density centrifugation

Cells within the blood will be separated based on density - stem cells are in the mononuclear layer, but there is lots of other cells within this.

• One way to get rid of these other cells is by a using a cocktail of antibodies, or a more advanced way is by magnetic- activated cell sorting - this is where you have an antibody which recognises an antigen on cell of interest and is magnetically tagged.

Master regulators of pluripotency

• OCT-4

• SOX-2

• NANOG

All transcription factors → all pluripotency factors

Stem cell transplant rejection

The human leukocyte antigen (HLAs) complex determines whether our immune system sees cells as self or non self.

HLAs are co-dominantly expressed

If therapeutic cells aren’t HLA matched they can be rejected

Immunosuppression is necessary to prevent rejection

Human pluripotent stem cells

Express HLA class I antigen but not class II so needs careful HLA matching, and cant just be used off the shelf.

When they differentiated into different phenotypes the HLA markers do change

Hypoimmunogenic induced pluripotent stem cells

CD47 is a tumour antigen that is implicated in the avoidance of phagocytosis.

It was thought if they can replicate this with pluripotent stem cells they would avoided by the immune system and so could be used as off the shelf therapy

Haematopoietic stem cells (HSC)

Adult stem cells which produce all blood cells. All blood cells in the body descend from a rare population of cells called haematopoietic stem cells.

Haematopoiesis is predominantly occurring in the red bone marrow, and a single HSC is capable of reconstituting the whole haematopoietic system

Therapeutic use of haematopoietic stem cells

Bone marrow/ haematopoietic stem cell transplantation

Can be autologous (transplanted from own individual) or can be allogenic (from genetically non identical) depending on indication.

Most common indication was Acute Myeloid leukaemia

A lot of the time the transplant is in myeloablative conditions, this is where you wipe out the patients existing haematopoietic system by total body radiation or chemotherapeutics

Issues with rejection if not HLA matched

Initailly patients are treated with granulocyte column simulating factor, causing HSC to migrate to the systemic circulation, and then isolate and purify from blood.

Main issues with HSCs

Graft vs Host Disease

T cells from the graft attacking the host due to seeing it as non self.

One way to limit this is by enrichment of CD34+ -magnetic activated cell sorting system. Main marker on HSCs is CD34 on the surface - if cells from the donor are incubated with an antibody that is magnetically tagged but recognises CD34 then it will stick to HSCs and cells like T cells without CD34 will pass through

Mesenchymal Stem Cells (MSC)

Wrapped around blood vessels and exist in a perivascular niche.

Main source of MSCs:

• Bone Marrow

• Adipose Tissue

• Umbilical Cord

Role of MSCs

Involved in homeostasis and repair of tissue - mechanisms are not fully understood.

Possible roles:

• Providing daughter cells which differentiate and participate in repair

• Home to sites of injury

• Secretion of factors that support wound repair by recruiting other cell types and modulating immune response

Therapeutic use of MSCs

Paracrine signalling

They can be used as off the shelf treatment as they don’t illicit immune response in a recipient

Not pluripotent so don’t proliferate indefinitely so don’t form teratomas

Have immunomodulatory function so can dampen down the immune system - so useful in prevention of graft and host disease

Potential as for delivery of therapeutic proteins

MSCs in the treatment of cancer

Can secrete micro- RNAs which can interfere with the signalling of cancer, toning down the proliferation of cells suppressing tumour growth.

MSCs can be engineered to secrete antitumor proteins and because they hone to the site of the infection, they can be injected into the patient when the hone to the tumour.

You can also load them fully of chemotherapeutic drugs because they will go straight to the tumour.

Techniques to purify cells (removing unwanted cells)

1) Differential adhesion - Some cells will stick to surfaces more than others

2) Density configuration - Size

3) FACs (florescent activated cell sorting) - Size, granularity, surface markers

4) MACs (magnetic activated cell sorting- surface markers)

Ways to scale up cell expansion

1) Microcarriers can be used to grow cells - increase surface area to volume ratio

2) Fluidised beds

3) Clusters of hollow fibres

4) Stirred tanks

Scaffolds materials

1) Polypeptides - Natural eg - collagen, gelatine, fibronectin, fibrin, laminin, silk, fibrin, zein

2) Polysaccharides - Hyaluronic acid, alginate, chitosan

3) Synthetic polymers

4) Bioceramics and bioactive glass

5) Deculturized tissue - take whole tissue/organ and take away cellular component, and grow cells on a matrix

Methods of scaffold formation

• Compression

• Solvent casting

• Particle leaching

• Freeze drying

• Spinning

• Electrospinning

• 3D Printing

Why is a 3D structure important in scaffolding

The 3D structure is important as we want to replicated cell signalling in the body

Electrospinning

Polymer is pushed out of a syringe driver at a slow rate with high voltage causing charge and repelling forming nanofibers - 3D scaffold, which you can collect on spinning collectors.

When these fibres line up, orientation of the fibres will increase - useful for tissues where you want alignment of cells. Eg - nerve and muscle fibres

Bioreactors

Most effective way to mature tissue in vitro, different physical and chemical cues may be required.

Simplest form of bioreactors is the stirred flask - the stirred flask will mature the tissue and stimulate growth of cells

Rotary bioreactors

This is a rotating system where you have a scaffold with cells floating in a stimulated system. All the time you’ve got medium flowing round and round, having nutrients flowing into the cell and waste coming out.

• This is gentler than the stirred tank as there is a balance of acting forces on the tissue

Using the body as a bioreactor

The body is the correct environment for tissue development, chemical signalling and mechanical forces. Insert the scaffold into the host and let the body do its work. You can generate such cells/tissues and use them as therapeutic applications.

It an acellular strategy which is an advantage over engineered tissues

Challenges of bioreactors - complexity of vascularisation

Vascularisation is a big issue in tissue engineering as cells need to be within 200um of a vessel to survive in the body.

Solutions:

• Seed scaffold with endothelial cells - randomly or using pre formed channels

• Incorporate vascular endothelial growth factors into scaffold

• Build scaffold around a vascular bed ex vivo

Bioreactors - way to form vascularisation

1) Take platelet rich plasma and sonicate it to break up all the cells. Then centrifuge off the membranes so that you have plasma full of growth factors.

2) You will have fibrinogen within this, so if you add thrombin and calcium in this you can have a gel network.

3) You can also have endothelial colony forming cells within this - and because the gel has lots of growth factors in, overtime the cells will be stimulated to grow and mature forming a vascular network

Challenges of 3D bioprinting

• Cell density

• Resolution

• Vascularisation

• Innervation

• Mechanical integrity

Myoseverin

can de differentiate cells promoting cell differentiation

Reversine

Can convert mononuclear cells into stem cells - these can then be dedifferentiated into other types of cells