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Flashcards in PSA Revision Deck (449)
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Effect of a P450 inducer?

Increase metabolism of P450, therefore drug exerts less of an effect


Effect of a P450 inhibitor?

Reduced metabolism of P450, therefore drug exerts more of an effect.


Examples of P450 Inducers ?

Increased enzyme activity, decreased drug concentration
- Phenytoin
- Carbamazepine
- Barbiturates
- Rifampicin
- Alcohol (chronic excess)
- Sulphonylureas


Examples of P450 inhibitors?


- Allopurinol
- Omeprazole
- Disulfiram
- Erythromycin
- Valproate
- Isoniazid
- Ciprofloxacin
- Ethanol (acute intoxication)
- Sulphonamides


Drugs to stop before surgery - COCP?

4 weeks before surgery


Drugs to stop before surgery
- Lithium

Day before


Drugs to stop before surgery
- Potassium sparing diuretics and ACEi?

Day of surgery


Drugs to stop before surgery
- Warfarin/heparin)
- Antiplatelets

- Variable.
Generally Warfarin is stopped and bridged with LMWH.


Drugs to stop before surgery -
Oral hypoglycaemic drugs and insulin?

Patient is NBM before surgery.

Metformin should be stopped because it will cause lactic acidosis.

In all cases - a sliding scale should be started instead - hourly blood glucose monitoring and adjust hourly dose.


Mnemonic for drugs to stop before surgery?

- Insulin
- Lithium
- Anticoagulants
- K-sparing diuretics
- Oral hydoglycaemics
- Perindopril


Management of long-term corticosteroids (pred) before surgery?

Increase steroid requirement
At IOA, patient should be given IV steroids.


Drugs to stop for a patient with haemoptysis?

Aspirin (Antiplatelet)
Enoxaparin (LMWH)


Drugs to stop patient is hyperkalaemic?

IV fluid with K should be stopped.

Also patient is receiving 6g of paracetamol so should be stopped.


Common pitfalls for prescribing?

Ensuring we have correct patient's prescription/drug chart

Noticing and recording allergies

SIgning the front of the chart.

Considering contraindications for each drug we prescribe.

Consider the route for each drug we prescribe

Consider the need for IV fluids.

Consider need for thromboprophylaxis

Consider need for antiemetics

Consider need for pain relief.


What is the PReSCRIBER mnemonic?

Patient Details
Sign the front of the chart
check for Contraindications to each drug
Prescribe Intravenous fluids if needed
Prescribe Blood clot prophylaxis if needed
Prescribe antiEmetic if needed
Prescribe pain Relief if needed.


When working on a new chart what must you write?

3 piece of patient identifying information on the front
- Patient Name
- Hospital Number


Reactions for drug charts?

Check allergy box to include any drug reaction

Don't forget that co-amoxiclav and Tazocin both contain penicillin.


Contraindications in drug charts? - Bleeding

Consider whether it is contraindicated.

Drugs that increase bleeding (aspirin, heparin and warfarin). Should not be given to those risk of bleeding (liver disease).

Prophylactic heparin is contraindicated in acute stroke - risk of bleeding.

Be wary that enzyme inhibitors AODEVICES can increase PT and INR.


Contraindications for drug chart - Steroids?

Side effects -
- Stomach ulcers
- thin skin
- Oedema
- Right + left heart failure
- Osteoporosis
- Infection
- Diabetes
- Cushing's syndrome


Contraindications for rugs - NSAIDS?

- No urine (renal failure_
- Systolic dysfunction (heart failure)
- Asthma
- Indigestion
- Dyscrasia (clotting abnormality)

Aspirin, whilst not technically an NSAID. It is not contraindicated in renal or heart failure.


Antihypertensives - SE?

Hypotension that may result from all groups of antihypertensives.

Bradycardia = beta blockers + CCBs .

Electrolyte disturbances with ACE and diuretics.

Individual drug classes have specific side effects
- ACEi = Dry cough
- Beta-blockers = wheeze in asthmatics
- CCB = Peripheral oedema and flushing
- Diuretics = renal failure. Loop diuretics can also cause gout.
Spironolactone causes


Route for patients?

if vomiting = antiemetics should be given by non-oral routes = IV/IM/SC

E.g Cycline 50mg 8hrly IV or PO
Metoclopramide 10mg 8 hrly.

If a patient is nil by mouth should still receive oral medication.


When are IV fluids prescribed?

As replacement for dehydrated/acutely unwell patient

As maintenance in patient who is nil by mouth.


Which fluid to prescribe?

0.9% saline UNLESS:

- Patient is hypernatraemic or hypoglycaemic: then give 5% dextrose instead.

- Has ascites: give human-albumin solution instead.

- Shocked with systolic BP <90: give gelofusine instead as it has high osmotic content so stays IV, thus stays intravascularly, maintaining BP for longer.

- Is shocked from bleeding: give blood transfusion, but a colloid first if no blood available.


How much fluid and how fast? - tachycardic or hypotensive

If tachycardic or hypotensive give 500ml Immediately in 10 mins

250ml if heart failure.

Then reassess patient, especially HR BP and urine output to assess response + speed of next bag.


How much fluid and how fast - oliguric (not due to obstruction)?

IL over 2-4hrs.

Then reassess HR, BP and urine output.


How volume depleted is a patient with reduced urine output (<30ml/h)

500ml of fluid depletion


How volume depleted is a patient with reduced urine output (<30ml/h) plus tachycardia?

1L of fluid depletion


How volume depleted is a patient with reduced urine output (<30ml/h), tachycardic plus is shocked?

Indicated >2L of fluid depletion.


Maintenance fluids requirements over 1 day?

Adults = 3 IV fluid per 24hrs
Elderly = 2L per 24hrs

Adequate electrolytes are provided by 1L of 0.9% saline and 2L of 5% dextrose.

1 salty and 2 sweet.

K+ = Bags of 5% dextrose or 0.9 saline containing KCL can be used. Patients require roughly 40mmol KCL per day = 20mmol KCL in 2 bags.

Never give IV potassium at more than 10mmol/hour.