Managing the Risks of Prescribing

Question 1

Yellow Card Scheme

Answer 1

Receives reports about SUSPECTED adverse drug reactions (ADRs) in the UK.

To submit a valid report to the scheme, you need to provide 4 items of info: identifiable patient; identifiable reporter; suspected reaction; suspect drug

Drugs include: prescriptions, vaccines, OTC, herbal remedies, e-cigs

Upside down BLACK TRIANGLE in BNF denotes medicines that require additional monitoring.

Question 2

Types of ADRs

Answer 2

Rawlins and Thomson:

• TYPE A > augmented. Are dose-related, common, predictable, related to pharmacology, unlikely to be fatal. E.g. bruising with warfarin, constipation with opioids.
• TYPE B > bizarre. Not dose-related, uncommon, unpredictable, often fatal. E.g. hypersensitivity to penicillin
• TYPE C > uncommon and related to cumulative dose. Time-related. E.g. suppression to the HPA axis with long-term corticosteroids.
• TYPE D > uncommon and usually dose-related. Occurs or becomes apparent sometime after use of drug. E.g. carcinogenesis.
• TYPE E > uncommon and occurs soon after withdrawal of the drug. E.g. opiate withdrawal syndrome
• TYPE F > common, dose-related, often caused by drug interactions. E.g. failure of oral contraceptive in the presence of enzyme inducer

**ADRs can also be classified based on their dose-relationship, their time-dependency and patient susceptibilities.

Question 3

Susceptibilities that increase risk of ADRs (IGASPED)

Answer 3

• Immunological reactions (e.g. allergies)
• Genetics (e.g. G6PD deficiency)
• Age (e.g. the elderly and children)
• Sex
• Physiology (e.g. pregnancy)
• Exogenous (e.g. other drugs the patient may already be taking, foods, temperature)
• Disease states affecting the patient (e.g. renal dysfunction, liver disease, CHF, which may influence prescribing)

Question 4

Drug-Drug Interaction (DDI)

Answer 4

When the effects of a drug are changed by the presence of another drug. Reported through the MHRA Yellow Card Scheme too.

Pt. factors that amplify DDIs:

• Age - older adults and neonates/children
• Sex - females increased risk
• Polymorphic enzyme expression
• Disease pathology - e.g. renal/liver failure will cause build-up of drug leading to toxicity
• Diet
• Smoking - causes accelerated removal of some drugs
• Illicit drug or alcohol intake

Question 5

Pharmacodynamic interactions

Answer 5

Makeup ~92% of DDIs.

Drugs amplify/negate each other’s pharmacological effects. Usually drugs with similar effects e.g. BB and CCBs. Occur at the level of the receptor, tissue, or organ.

E.g. interactions between Sildenafil and GTN by having similar effects on the expression of cyclic GMP - can lead to severe hypotension/MI

Warfarin DDIs: Users advised not to change their diet suddenly with regard to green leafy veg and other food stuffs with significant amounts of vit K in

Question 6

Pharmacokinetic interactions

Answer 6

Makeup around 5% of DDIs.

Occur when one drug, dietary or herbal chemical, impacts on the biotransformation of the drug, or even their distribution within the body.

E.g. Rifampicin and OCP - Rifampicin induces cytochrome P450 enzyme therefore reduces effectiveness of both oestrogens and progestogens, so contraceptive cover reduces too.

Question 7

CYP inducers (i.e. will eliminate active drug quicker)

Answer 7

• Rifampicin
• St. Johns Wort
• 1st gen anti-convulsants e.g. phenytoin, carbamazepine, phenobarbital
• Tobacco
• Alcohol

Question 8

CYP inhibitors (i.e. will lead to accumulation of active drug)

Answer 8

• Reversible > azole anti-fungals e.g. fluconazole
• Irreversible > erythromycin
• Grapefruit (canned fruit, juice or peel)
• Cranberry juice

Question 9

Herbal preparation-drug interactions

Answer 9

GARLIC > inhibits platelet aggregation, increased risk of bleeding with anticoagulants e.g. warfarin

GINSENG > minor hypoglycaemic activity, therefore interacts with oral hypoglycaemic agents (e.g. gliclazide)

GLUCOSAMINE > interacts with warfarin

ST. JOHNS WORT > interacts with anti-depressants. Increase risk of serotonin syndrome or hypertensive crisis when prescribed with MAOIs; interacts with warfarin by inducing its metabolism leading to reduction in INR; interacts with OCPs reducing contraceptive cover.

LIQUORICE > can cause hypokalaemia and therefore increase risk of digoxin toxicity if taken concomitantly.

Question 10

Types of human error

Answer 10

Mistake - error in formulating a plan

Slip - when one or more step is executed incorrectly. Occur when actions are automatic and do not require conscious thought. Likelihood increases due to psychological factors, physiological factors (e.g. fatigue), environmental factors (e.g. noise, heat, visual stimuli)

Lapse - when one or more step is omitted. Occur when actions are automatic and do not require conscious thought. Can’t be improved by more training as automatic.

Violations - deliberate - although perhaps not reprehensible - deviation from regulated codes of practices or procedures

(Mistakes can be classified as either KNOWLEDGE based or RULE based)

Question 11

Responding and Reporting Medication Errors

Answer 11

Respond:

• Provide prompt and appropriate clinical treatment to prevent further harm to pt.
• MDT discussion to determine level of response required
• Timely and open discussion with the pt.

Report:

• Report at a local level even if no harm has happened.
• Report submitted to the National Reporting and Learning System (NRLS)

**Large healthcare organizations should have an identified individual as the Medication Safety Officer (MSO)