Blood Flashcards
list three antiplatelet (ADP receptor) drugs
clopidogrel
ticagrelor
prasugrel
clopidogrel, ticagrelor and prasugrel belong to which drug class?
Antiplatelets (ADP-receptor agonists)
list three indicatiosn for prescription of antiplatelet drugs?
- treatment of ACS
- prevention of coronary artery stent occlusion
- long-term secondary prevention of thrombotic arterial events in pts w cardiovascular, cerebrovascular and peripheral arterial disease
antiplatelet drugs are commonly prescribed with which other drug?
aspirin
MOA of antiplatelets?
prevent platelet aggregation by binding to ADP receptors (P2Y12 subtype) on platelet surface.
The MOA of antiplatelets is synergistic/additive with that of aspirin?
synergistic: ADP binding process is independant of the COX pathway
what is the most common adverse effect of antiplatelets?
Bleeding
GI upset (common)
Thrombocytpenia (very rare)
list contraindications to prescribing antiplatelets
pts with active bleeding
elective surgeries (should be stopped 7 days prior)
renal and hepatic impairment should be used with caution
clopidogrel is a pro-drug which requires metabolism by which hepatic enzyme?
cytochrome P450 (CYP enzymes)
which class of drug may inhibit the efficacy of clopidogrel?
CYP inhibitors i.e. omeprazole, ciprofloxacin, erythromycin
are ticagrelor and prusagrel also pro-drugs?
prasugrel yes- less suceptible to interactions
ticagrelor no- but interacts with CYP inhibitors possibly inc risk of toxicity
available preparation of clopidogrel?
only oral preparaption
low doses of clopidogrel require how long to reach their full anitplatelet effect?
up to a week
if rapid effect required what loading dose of clopidogrel should be prescribed?
this is followed by what maintainence dose?
300mg orally for ACS
once only before commencing maintainence dose of 75mg orally daily
how should clopidogrel use be comunicated to the pt?
used to reduce risk of MI or strokes and ot prolong life
if treatment following stent insertion emphasise importance of continuing treatment and usually for 12 months
is clopidogrel a reversible drug?
NO it is irreversible- takes up to 7-10 days (lifetime of a platelet) for its antiplatelet effect to wear off
what kind of drug is aspirin?
antiplatelet
common indications for aspirin use?
- treatment of ACS and acute ischaemic stroke
- long-term secondary prevention of thrombotic aarterial events in pts with cardiovascular, cerebrovascular and peripheral arterial disease
what is the MOA of aspirin?
irreversibly inhibits cyclooxygenase (COX) reducing production of factor thromboxane
how long does the antiplatelet effect of aspirin last?
the lifetime of a platelet
(platelets do not have a nuclues to synthesis new COX)
what are the common adverse effects assoc with aspirin?
GI irritation
peptic ulceration, haemorrhage, bronchospasm (hypersensitivity)
*life threatening in overdose*
why can aspirin not be given to children under 16 years?
risk of Reyes syndrome
life threatening illness affecting liver and brain
who should not be prescribed aspirin?
those with aspirin hypersensitivity
third trimester of pregnancy (prosaglandin inhibition may lead to premature closure of ductus arteriousus)
those with peptic ulcers (prescibe gastroprotection)
gout- can trigger ana cute attack
what prepararions of aspirin are available?
oral and rectal
how should aspirin be prescribed for 1. ACS and 2. acute ischameic stroke?
- 300mg loading dose followed by 75mg daily
- 300mg daily for 2 weeks
(75mg daily for long-term prevention fo thrombosis)
why should aspirin be taken with or after food?
minimise gastric irritation
*those who are high risk for GI upset should be coprescribed gastric protection i.e. omeprazole 20mg daily
name the 4 most common direct oral anticoagulants or DOACs?
apixaban, dabigatran, edoxaban, rivaroxiban
list two common indications for DOACs
- venous thromboembolism (DVT and PE)
- AF (prevent stroke and sytemic embolism)
what is teh MOA of DOACs?
act on the final common pathway of coagulation cascade:
apixaban, endoxaban, rivaroxaban inhibit activated factor X (Xa)
dabigatran inhibits thrombin (inhibits conversion of fibrinogen to fibrin)
what are the common adverse effects of DOACs?
bleeding: greater GI bleed risk than warfarin but lower risk of major bleed or intracranial haemorrhage
others: anaemia, GI upset, dizzness, elevated liver enzymes
DOACs should be avoided in which groups of people?
active, clinically significant bleeding
those with risk factors for major bleeding i.e. peptic ulcers, cancer, recent surgery
hepatic/ renal disease- DOACs can be esxcreted using CYP enzymes
DOACs are contraindicated in which patient groups?
preganancy and breastfeeding
what is the dosing regimen for DOACs?
varies by indication
duration also varies
how are DOACs prepared?
oral preparation
advantage obver heparin in outpatient or prevention/treatment of VTE
altepase and streptokinase belong to which class of drug?
fibrinolytic drugs
when is the use of finbrinolytics indicated?
- acute ischaemic stroke
- acute st elevation MI
- massive PE with haemodynamic instability
what is the MOA of fibrinolytics?
catalyse conversion of plasminogen to plasmin
*plasmin acts to dissolve fibrinous clots
fibrinolyitcs are otherwise known as?
thrombolytic drugs
list some adverse effects of fibrinolytics?
N&V, brusing, hypotension
serious bleeding, allergic reaction, cardiogenic shock and cardiac arrest require treatment to be stopped immediately
contradindications to thrombolysis using fibrinolytics include?
bleeding (recent trauma/surgery, disorders)
intracranial haenorrhage (must undergo CT prior to treatment)
previous treatment with streptokinase
risk of haemorrhage is increased in patients given fibrinolytics if they are also takin what drugs?
anticoagulants and antiplatelets
how are fibrinolytics administered?
given IV as bolus or infusion
should only be prescribed and administered by clinicians with epertise in their use
how can you describe fibrinolytics (thrombolyse) to patients and next of kin?
‘clot busting drug’ to dissolve clot and restore blood flow
how should pts be monitored follwing fibrinolytic therapy (thrombolyses)?
pts should be in HDU with vital signs checked every 15 mins in first 2 hrs
heparin is indicated for what (2)?
- primary prevention of DVT and PE (can also initially treat VTE until oral anticoag i.e. warfarin/DOAC)
- ACS - used with antiplatelet agents to reduce clot progression
what is the MOA of heparin?
enhances anticoagulant effect of antithrombin (AT)
what is the main adverse effect of heparin?
haemorrhage
hyperkalaemia occurs occasionally
anticoagulants should be used with caution in which pt groups?
those at increased risk of bleeding
- clotting disorders
- recent surgery/trauma
- severe uncontrolled HT
anticoagulants i.e. heparin shoil dbe withheld immediatley before and after which procedures?
invasive procedures such as LP and spinal anaethesia
combining heparins with other antithrombotic drugs i.e antiplatelets, warfarin has what effect?
additive effect
(can be desirable in ACS but otherwise assoc w inc risk of bleeding so should be avoided)
protamine is a option to reverse which drug if major bleedign presents?
reverses heparin
in renal impairment which anticoagulant is preffered due to risk of accumulation?
LMWH accumulates so lower dose of UFH should be used instead
how are heparins commonly administered?
SC injection- abdo wall and not arm
how could you explain heparin injections to a patient?
a daily injection to reduce risk of blood clots
in special cases i.e. renal impairment, pregnancy how can heparin levels be monitored?
plasma antifactor Xa activity
in prolonged therapy >4days, platelet count and serum K+ conc should be measured
when warfarin is used for VTE treatment why is antoher anticoagulant i.e. LMWH given alongside initially?
LMWH provides ‘bridging anticoagulation’ during the period where warfarin may be briefly pro-thrombotic before its effect on clotting factors
common indications for prescribing iron? (2)
- treatment of iron-deficiency anaemia
- prophylaxis of iron-deficiency anaemia (those w risk factors- poor diet, malabsoprtion, menorrhagia)
describe the MOA of iron and its absorption
essential for erythropoiesis and synthesis of haem
best asorbed in its ferrous state (Fe2+) in duodenum and jejunem
most common adverse effect of iron?
GI upset- nausea, epigastric pain, constipationa and diarrhoea
(can have black bowel movements on treatment)
iron should be used with caution in which patient groups?
atopic predisposition- risk of anaphylactic reaction
intestinal disease- exxacerbate symptoms
iron reduces absorption of which drugs (2)?
levothyroxine and biphosphonates
(should be taken at least 2hrs before oral iron)
how is iron available for prescription? (2)
oral and IV administration
how should iron be administered?
oral iron on an empty stomach (or with food to reduce GI upset)
IV injection over 10mins or infusion
how can you communicate the effects of iron to the patient?
used to top up iron stores to improve symtoms of anaemia- shoul dadvise it may take a few months to feel the full benefit
how should iron administration be monitored?
FBC until haemoglobin has returned to normal
(should expect Hb rise by around 20g/L per month)
people with iron deficiency often require a colonoscopy to investigate- what should be done with regards to iron therapy prior to scope?
iron treatment stopped 7 days before scope
(iron can make stool balck and sticky making it difficult to visualise anything)
list some common vitamins and their indications (4)
Thiamine B1- Tx and prevention of Wernickes encephalopathy and Korsakoff’s psychosis
Folic acid- megaloblastic anaemia and 1st trimester to reduce risk of neural tube defects
Hydroxocobalamin B12- megaloblastic anaemia and subacute combined degeneration of the cord (from B12 deficiency)
Phytomenadine Vit K- newborns to prevent vit K deficiency bleeds and to reverse warfarin
which two vitamins are important to give simultaneously if combined deficiency?
Vit B12 and folate
(replacing folate alone is assoc w neurological maifestations of B12 deficiency)
pabrinex is given for which deficiency?
thiamine deficiency
how is treatment with B12 and folate monitored?
FBC
common indications for warfarin (2)?
- VTE (DVT and PE)
- prevention of arterial embolism in pts w AF or prosthetic valves
MOA of warfarin?
inhibits vit K and in turn:
inhibits factors 2, 7, 9, 10 and proteins C and S
main adverse effect of warfarin
bleeding
warfarin should be used with caution in which pt groups?
risk of haemorrhage i.e. after surgery/trauma
liver disease (less able to metabolise drug)
1st trimester (teratogenicity risk)
changes in which enzyme can significantly change the anticoagulation effect of warfarin?
cytochrome P450 (CYP)
traditionally when is warfarin taken for consistent effects on the INR?
6 o’clock so consistent effect on INR the following morning
how can you comunicate warfarin use to pts?
balance between preventing clots and bleeding
will recieve anticoagulant book ‘yellow book’ to record doses, test results
what does the INR measure?
prothrombin time of a person
what is important to consider when looking at INR following a dose change in warfarin?
changes in INR lag behind dosing changes- look back over last 48-72hrs to see what doses have led to the current INR
