Basic principles of prescribing Flashcards by Katherine Neo

oxybutynin side effect

Antimuscarinic

memory loss
dry mouth
constipation
blurred vision

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adherence definition

the extent to which the the pt’s behaviour matches agreed recommendations from the prescriber

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compliance definition

the old term for adherence:

the extent to which the the pt’s behaviour matches agreed recommendations from the prescriber

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what is concordance

a process of prescribing and medicine taking based on partnership

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Diclofenac adverse effect

dyspepsia (NSAID)

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indapamide adverse effect

gout (thiazide diuretic)

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lisinopril adverse effect

intractable cough

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prednisolone adverse effect

alter mood and behaviour

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prochlorperazine adverse effect

ESPSE like dystonia (antipsychotic)

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what is intentional non-adherence

the pt makes a conscious decision not to follow treatment recommendations

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what is non-intentional non-adherence

the pt wants to follow treatment instructions but is prevented from doing so by certain factors

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at what age are patients entitled to free prescriptions

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how many half lives will it take to clear 97% of the drug from the body

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how does erythromycin effect warfarin

it inhibits warfarin metabolism

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how does phenytoin effect other antiepileptics

it increases metabolism of other antiepileptics

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how does rifampicin affect oestrogen in the COCP

it increases the metabolism of oestrogen

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what is the first pass effect

the concentration of a drug, specifically when administered orally, is greatly reduced before it reaches the systemic circulation

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what is the volume of distribution

the theoretical volume of fluid that would be needed to achieve the actual plasma drug concentration

total amount of drug in the body / plasma drug conc

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what is zero order elimination

Elimination of a constant quantity per time unit of the drug quantity present in the body

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what is first order elimination

Elimination of a constant fraction per time unit of the drug quantity present in the body. The elimination is proportional to the drug concentration

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elimination rate constant formula

k = clearance / volume distribution

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what does it mean when a drug induces the P450 system e.g. phenytoin

can accelerate the metabolism of concomitant drugs

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what does it mean when a drug inhibits P450 e.g. erythromycin

can slow down the metabolism of other drugs

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what are pro drugs

medicines or compounds that are converted (or activated) to pharmacologically active forms within the body

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what is an agonist

a chemical that binds to its target to increase its activity

what is an antagonist

a chemical that opposes the action of another chemical

define affinity

the tendency of a molecule to bind to a receptor

define efficacy

how well an agonist achieves a response

what is a partial agonist

a drug that has a lower maximal response resulting from lower efficacy

what are allosteric modulators

they bind to proteins atd site other than the site for the principal agonist

what is the greatest risk in overdose of TCA

ventricular dysrhythmias

why are statins given at bed time

the enzyme HMG CoA reductase is more active at night. Statins inhibit it which decreases synthesis of cholesterol

what is ED50

the dose required to elicit 50% of a maximal response

calculation to estimate a child's body weight

(age + 4) x 2(kg)

how many micrograms in 1mg

1000

how many nanograms in 1 microgram

1000

what is % w/w

percentage weight per weight e.g. hydrocortisone 0.5% w/w contains 0.5g of hydrocortisone in 100g of the cream

what is % w/v

percentage weight per volume e.g. NaCl 0.9% contains 0.9g of NaCl in 100ml of the infusion

what is % v/v

percentage volume per volume e.g. ChloraPrep, containing isopropyl alcohol 70% v/v contains 70ml isopropyl alcohol in 100ml solution

how much adrenaline is in 1 in 1000

1g in 1000ml so 1mg per ml

how much adrenaline is in 1 in 200,000

1g in 200,000ml so 5 micrograms per ml

how many lbs in a stone

how many grams in 1lb

450g

how many kg is 1 stone

6.35kg

how many cm in 1 inch

2.54cm

how many cm in 1 ft

30.48cm

in obese patients, gentamicin should be dosed to which body weight?

ideal body weight

on the BNF how do you find the opioid conversions?

treatment summaries --> prescribing in palliative care

on the BNF how do you find steroid conversions?

trx summaries --> glucocorticoid therapy

on the BNF how do you find the benzodiazepam conversions?

trx summaries --> hypnotics + anxiolytics

what should vancomycin be diluted up to?

5mg/ml and run at a rate not exceeding 10mg/min

what body weight should be used when calculating the dose for acetylcysteine?

actual body weight (max 110kg)

what should acetylcysteine be diluted in

glucose

describe the 3 part dose regimen of acetylcysteine

1) loading dose over 1h in 200ml glucose 5% 2) next dose over 4h in 500ml glucose 5% 3) final dose given over 16h in 1L glucose 5%

formula for volume of parenteral drug required to be administered or added to a infusion

volume required = (what you want/what you get) x what it's in

why should alendronic acid not be crushed

Biphosphonates should not be crushed because they can cause adverse GI affects

why is diclofenac CI'd post stroke

increased risk of thromboembolic event

can indapamide be crushed

yes

can nifedipine be crushed

what is bioavailability

the proportion of the medicine which finally makes it to the systemic circulation where it is available to act at the 'effector site'

what is the bioavailability of IV medicines

100%

name 3 commonly prescribed drugs where the bioavailability changes depending on the route

- morphine - ciprofloxacin - digoxin

how should ciprofloxacin be taken

- NOT with a glass of milk | - at different times to indigestion medication

why should there be a 'nitrate free period' of at least 8 hours

to prevent pts from developing a tolerance to the medicine

common drugs which interact with the enteral feed

- quinolones | - phenytoin

what can aid the absorption of iron salts

vit C (ascorbic acid)

why are enteric coated formulations CI'd in pts with an ileostomy

EC meds bypass the stomach and get absorbed in small intestine which is not possible if pt has ileostomy

are MR formulations appropriate for pts with an ileostomy

should you check gentamycin serum conc levels after giving 1 stat dose?

no need to unless planning to give another dose

what are bacteriostatic agents

they inhibit protein synthesis, stopping the cell from growing they don't kill the cell, but allow host defences to deal with the infection

Name some bacteriostatic agents

macrolides (clarithromycin) tetracyclines (doxycycline)

what are bactericidal agents

they inhibit a vital cellular process which leads to cell death

name some bactericidal agents

aminoglycosides (gentamicin)

what infection is co-amoxiclav associated with

c.difficile infection. Diarrhoea!

c.difficile infection mnx

1. send stool cultures to test for c.difficile toxin + antigen 2. stop co-amoxiclav or suspected drug 3. give narrow spectrum agent if needed for her pneumonia 4. start empirical metronidazole whilst awaiting stool culture

why are urine dipsticks an unreliable method for catheter related UTIs

urinary catheters quickly become colonised with bac and the dipstick will only detect their presence

which group of bacteria is vancomycin affective for

gram positive

how do you know if a drug is controlled

Schedule 2 and 3 preparations are labelled as CD2 or CD3 next to the drug in the BNF

what is meant by unlicensed drugs?

do not have UK marketing authorisation

what is meant by off label

has marketing authorisation but used outside the terms of its license

should tacrolimus be prescribed a a brand or drug name?

brand - to minimise the risk of inadvertent switching between products, which has been associated with reports of toxicity and graft rejection.

what is medicines reconciliation

ensures that the medicine prescribed on admission correspond to medicine prescribed before admission

what is the max dose of simvastatin when prescribed with amlodipine

20mg

what medicines should be omitted from an MDS

- Aspirin (likely to disintegrate) - cytotoxic drugs e.g. methotrexate as handling shold be kept to a minimum - PRN meds - chewable tablets

which medicines can reduce the effectiveness of the COCP

Cytochrome P450 inducers e,g, carbamazepine

equation to calculate eGFR in neonates

30 x height (cm) / serum creatinine (micromol/L)

equation to calculate eGFR in child>1y

40 x height (cm) / serum creatinine (micromol/L)

when should a Yellow card be submitted in <18y

all serious adverse drug reactions that result in harm and suspected ADRs to new vaccines/drugs

what can't F1's prescribe

- parenteral nutrition | - cytotoxic or immunosuppressants except corticosteroids