Pharmacology 💊 Flashcards
What is the source and chemistry of heparin?
- Natural sulfated polysaccharide present in mast cells & carries –ve charge
- It is high molecular weight 30000 dalton. “Widely changes which causes problems”
What is the route of administration of heparin?
Not taken orally as it precipitated by gastric HCl (given by IV, SC)
Does heparin cross BBB?
Cannot cross BBB or placenta (safe in pregnancy).
What is the onset and duration of heparin?
Rapid onset & short duration (t1/2 60 min.) “used in emergencies”
What is the mechanism of action of heparin?
- Its action depends on the presence of a natural clotting inhibitor called antithrombin III.
- Small quantities of heparin can activate antithrombin III inhibition of several clotting factors especially [factor X & thrombin (factor II)].
where does Heparin act?
In vivo & in vitro
What are the therapeutic uses of heparin?
- Treatment of established thrombosis “prevent propagation”
- Prevention of thrombosis “bid-ridden patients and artificial parts of the body”
- Keep coagulation time & activated partial thromboplastin time (APTT) at 2-3 times of its normal value (for Control of Therapy).
What are the adverse effects of Heparin?
- Bleeding is the most common and dangerous SE can be reversed by antidote protamine sulfate “physical antagonism” a basic +ve charged protein that combines with heparin.
- Heparin-induced Thrombocytopenia “decreased platlets” (HIT) (autoimmune). arises from the development of antibodies to the heparin–platelet factor 4 complex. “Thrombocytopenia + thrombosis”
- Hematoma if given IM
- Osteoporosis
- Alopecia
What is the nature of LMWH (enoxaparin)?
❖ Standard (unfractionated) heparin is a mixture of different molecular weight fractions (MW 3000-30,000 Da) that can affect more than one coagulation factor and produce thrombocytopenia (↑ risk of bleeding).
LMWH has molecular weight less than 8000 dalton which causes more specificity
What is the molecular weight of LMWH and what is the significance of that?
❖ LMWH has a MW less than 8000 Da that makes it specific for factor X with minimal effects on platelets and other clotting factors. “Not like heparin which activates antithrombin III that inhibits many factors”
Compare between unfractionated heparin and LMWH according to:-
Molecular weight range anti-factor 10 activity Nonspecific binding to plasma proteins Bioavailability after subcutaneous injection Half-life Thrombocytopenia Risk of bleeding Lab monitoring
High - low
Less specific - more specific
High - low
Low (due to binding to S.C tissue) - High
Short (3 daily) - long (once daily)
Common 10% - less common (<2%) (less affinity for platlet factor 4)
High “all coagulation factors” - low
APTT (essential) - extent of inhibition of factor Xa (may br unnecessary)
Give examples for synthetic factor X inhibitors.
Fondaparinux
Rivaroxaban
What is the nature of Fondaparinux?
Synthetic pentasaccharide that have the same mechanism like LMWH (i.e. selective inhibitor of factor Xa).
What is the route of administration of Fondaparinux?
It is given by s.c. injection once daily (has long t1⁄2).
What is the route of administration and it is the mechanism of action of Rivaroxaban?
- Oral inhibitor of (factor Xa).
- Bind to the active site of factor Xa Preventing its ability to convert prothrombin to thrombin
Give examples for direct thrombin inhibitors.
Argatroban (parenteral) Dabigatran (Oral)
What is the use of DTIs?
alternative to heparin to treat patients with heparin- induced thrombocytopenia
What is the Chemistry and nature of DTIs?
A “SDCTI” selective direct competitive thrombin inhibitor that binds to and inhibits both circulating and thrombus-bound thrombin (factor II a).
What is the source and the chemistry of warfarin?
Synthetic coumarin compound
What is bioavailability of warfarin?
Good (bioavailability is 100%).
Can warfarin pass BBB and the placenta?
Yes
Does warfarin bind highly to plasma proteins?
Highly bound to the plasma proteins “causes drug interactions”
What is the enzyme that is responsible for Biotransformation of warfarin?
hepatic CYP450.
What is the mechanism of action of warfarin?
- Warfarin inhibits vitamin K epoxide reductase enzyme in the liver leading to inhibition of formation of the active form of vitamin K → ↓ synthesis of vitamin K-dependent clotting factors (II, VII, IX, and X).
- The action of warfarin could be antagonized by vitamin K.
What are the therapeutic uses of warfarin?
Warfarin is given oral 2-10 mg/day for prevention and treatment of thrombosis. “But not in emergency”
How is warfarin monitored?
- Monitoring is by prothrombin time (PT) or International Normalized Ratio (INR): It is the ratio of the PT in the patient to that of normal person.
- It must be kept 2-3 times as the normal value. “Like heparin”
What are the adverse effects of warfarin?
- Bleeding: gingival “related to gums” bleeding, nose bleeding…
It could be treated by the following:
• Immediate stopping of the drug.
• Fresh frozen plasma (FFP). “Has clotting factors”
• Vitamin K1(phytomenadione): to enhance synthesis of clotting factors.
- Teratogenicity: serious birth abnormalities “fetal warfarin syndrome”
- Serious thrombosis: on sudden withdrawal
What are the drug interactions of warfarin?
- Drugs that potentiate↑ warfarin action:
1) Liquid paraffin: ↓ vit K absorption
2) Oral antibiotics: ↓ vit K synthesis by killing the gut flora
3) NSAIDs: displace warfarin from pp.
4) Microsomal enzyme inhibitors (e.g. cimetidine, chloramphenicol) ↓ metabolism of warfarin. - Drugs that inhibit warfarin:
1) Aluminum hydroxide: ↓ warfarin absorption
2) Oral contraceptives and vit K. ↑ synthesis of clotting factors
3) Microsomal enzyme inducers (e.g. phenobarbital, rifampin) ↑ metabolism of warfarin.
And compare between heparin and warfarin according to: –
Source Action Kinetics Mechanism of action Dose Control Onset Duration Antidote
Natural - Synthetic
In vivo and in vitro - In vivo
Absorbed from GIT, Cross the placenta and milk
It activates antithrombin III - They compete with Vit. K. on vit K epoxide reductase
S.C - oral
Blood coagulation time APTT - prothrombin time, INR
Immediate - Delayed1-3 days
Short 2-4 hrs - Long 4-7 days
Protamine sulphate + Fresh blood transfusion - Vitamin K +Fresh blood transfusion
why is pregnancy considered as a hypercoagulable state?
due to increase levels of coagulation factors and venous stasis.
What does pregnancy increase the risk of? “related to blood”
Pregnancy increases the risk of venous thrombosis and pulmonary embolism in susceptible female.
What does the use of warfarin in the first trimester and in the last trimester cause?
The use of warfarin in the first trimester is associated with birth defects (5%), while its use near full-term increases the risk of fetal hemorrhage.
What are the side effects of heparin and low molecular weight heparin during pregnancy?
Neither UFH nor LMWH cross the placenta; therefore, do not cause fetal bleeding or teratogenicity, but they can reduce bone mass density and cause osteoporosis if used through pregnancy.
What is anticoagulation recommended for pregnant women?
Anticoagulation is recommended in most pregnant patients with a mechanical heart valve.
What does the American College of chest physicals recommend regarding the use of anticoagulants during pregnancy?
- The American College of Chest Physicians (ACCP) recommends the use LMWH until 13 weeks’ gestation, then change to warfarin until the patient is close to delivery (34 weeks), and then restart LMWH.
- Long-term anticoagulants should be resumed postpartum
What are types of drugs used to stop coagulation? (Anti-platlets)
1- Aspirin (Acetyl salicylic acid)
2- ADP receptor blockers
3- Gp IIIA/IIB receptor blockers
4- PDE inhibitors
What is the mechanism of action of aspirin?
- Irreversible inhibition of COX enzyme → ↓ TXA2 → ↓ platelet aggregation.
- Irreversible acetylation of platelet cell membranes → ↓ platelet adhesions. “To collagen”
- Decrease platelet ADP synthesis → decrease platelet accumulation
What is the duration of aspirin?
It lasts 7-9 days. “As it inhibits COX irreversibly, so new platelets must be formed”
“Platlets must be present in cases of surgery”
what are the types of doses of aspirin and what does each dose cause?
- At higher doses (> 325 mg/day), aspirin may decrease endothelial synthesis of Prostacyclin (PGI2), which inhibits platelet activity
- Low doses (75-150 mg/day) ↓ synthesis of platelet TXA2 “in platlets” more than PGI2 in endothelial cells and avoid this effect.
What are ADP receptor blockers?
Ticlopidine, Clopidogrel, Prasugrel
What is the mechanism of action of ADP receptor blockers?
Irreversibly inhibit the binding of ADP to its receptor “while aspirin prevents its synthesis” on platelets → inhibit the activation of the glycoprotein IIb/IIIa receptors “common on all antiplatlets” required for platelets to bind to fibrinogen and to each other
What is the nature of clopidogrel and what is the enzyme responsible for its biotransformation?
Is a prodrug → activated in the liver by CYP2C19.
What are poor metabolizers of clopidogrel?
Some people have genetic deficiency in the enzymes that metabolize clopidogrel; they are called “poor metabolizers” and cannot benefit from this drug.
“Those with liver problems as well”
What are the uses of clopidogrel?
❖ prophylaxis of thrombosis in both cerebrovascular and cardiovascular disease (e.g., coronary artery disease, coronary angioplasty, peripheral vascular disease, etc.).
What are gp IIb/IIIa receptor blockers?
Abciximab, Eptifibatide, Tirofiban
What is the nature of abciximab?
the Fab fragment of a monoclonal antibody
What is the nature of eptifdibatide?
small synthetic peptide “rattle snack venom”
What is the nature of tirofiban?
peptide of low MW
What is the mechanism of action of gp IIb/IIIa receptor blockers?
They bind to gp IIb/IIIa and blocks binding of platelets to fibrinogen. “Prevent final stage”
What are the uses of gp IIb/IIIa receptor blockers?
❖ Approved for use in patient undergoing percutaneous coronary intervention, for unstable angina, and for post-MI. “Revise the notes for these terms”
What is the mechanism of action of PDE inhibitors?
Dipyridamole inhibits phosphodiesterase (PDE) enzyme → ↑cGMP → VD and inhibition of platelet activity.
Give an example for PDE inhibitors.
Dipyridamole
What are the uses of PDE inhibitors?
limited to pro phylaxis (combined with warfarin ) in patients with prosthetic ( mechanical) heart valves.
What is the classification of fibrinolytics? “all IV”
Non-fibrin selective: Streptokinase and urokinase “bind to any plasminogen”
Fibrin selective: recombinant tissue plasminogen activator (rt-PA) “work on fibrin-bound plasminogen”
What is the nature of streptokinase and what is its mechanism of action?
Streptokinase is a protein that is isolated from streptococci; it activates plasminogen into plasmin non-enzymatically.
Is streptokinase antigenic?
It may be antigenic (causes allergy) in some people.
What is the nature of urokinase and what is it prepared from now?
Urokinase is a protease originally isolated from urine, It is now prepared in recombinant form from cultured kidney cells.
Which is more antigenic? streptokinase or urokinase
It is less antigenic than streptokinase.
Give examples for recombinant tissue plasminogen activators “the best fibrinolytics”
Alteplase, Reteplase, Tenecteplase
What differentiates recombinant tissue plasminogen activators?
They are most specific to fibrin-bound plasminogen
Are recombinant tissue plasminogen activators antigenic?
Not antigenic or allergic
What are the therapeutic uses of thrombolytic drugs?
❖ Acute myocardial infarction, ischemic stroke, pulmonary embolism, arterial thrombosis.
❖ In cases of acute MI, they should be given within 1h of onset. The maximum benefit is obtained if treatment is given within 90 minutes of the onset of pain. “The faster, the better”
❖ Before thrombolysis, care should be taken to ensure there is no liability for bleeding in a critical sit e.g., retina, CNS, etc.
What are the adverse effects of thrombolytic drugs?
1) Systemic bleeding is the major adverse effect:
- The risk is high with streptokinase and low with the recent recombinant tissue plasminogen activators.
2) Streptokinase can cause allergy, fever, and hypotension during I.V. infusion. (HAF)
What are types of coagulants and hemostatics?
Local agents and systemic agents
What are the local agents for coagulation and hemostatics?
- Physical methods: application of pressure, cooling, or heat coagulation.
- Vasoconstrictor drugs: e.g., adrenaline nasal pack in epistaxis.
- Astringents: drugs which precipitate surface proteins e.g., Alum sulphate. “Close bleeding surface”
- Thrombin and thromboplastin: applied on the bleeding surface as powders.
- Fibrin and fibrinogen: available as dried sheets and used in surgery.
What are the systemic agents for coagulation and hemostatics?
- Vitamin K: essential for synthesis of factors II, VII, IX, X by the liver.
- Fresh blood or plasma transfusion: as sources of coagulation factors.
- Plasma fractions:
a) Thromboplastin (factor III): prepared from mammalian tissues.
b) Antihemophilic globulin (factor VIII): given in hemophilia A.
c) Calcium (factor IV): as a coagulation factor. - Aminocaproic acid and Tranexamic acid: inhibitors of fibrinolytic system.
What are the types of vitamin K?
1) Vitamin K1 (Phytomenadione):
- Naturally occurring fat-soluble vitamin present in green vegetables.
- It is available clinically in oral and parenteral forms.
2) Vitamin K2 is synthesized by intestinal bacteria.
What does vitamin K dissolve in?
Both vitamins K1 and K2 require bile salts for absorption “as they are fat soluble” “in case of oral” from the intestine.
What is the mechanism of action of vitamin K?
Vitamin K is required for posttranslational modification of clotting factors II, VII, IX, and X (1972) by liver cells.
What are the therapeutic uses of vitamin K?
1) To reverse bleeding episodes caused by overdose of warfarin, and salicylates.
2) To correct vitamin deficiency caused by dietary deficiency, or in patients receiving oral antibiotics. “That kill bacteria that form vit K”
3) To prevent hypothrombinemia of the newborn: all newborns should routinely receive 1–2 mg of vitamin K directly after birth (especially in premature infants).
What are the adverse effects of vitamin K?
Parenteral vitamin K1 is dissolved in oil; rapid i.v. administration can cause dyspnea, chest pain, or even death. “Must be slow”
What is the nature of caproic acid and tranexamic acid?
- Aminocaproic acid is a synthetic agent that competitively inhibits plasminogen activation.
- Tranexamic acid is more potent analogue of aminocaproic acid. “Gives same response with lower dose”
Give examples for fibrinolytic inhibitors
Aminocaproic acid and Tranexamic acid
What are the uses of fibrinolytic inhibitors?
1) To prevent bleeding from tissues rich in plasminogen activators e.g., lung, prostatic surgery, menorrhagia, and ocular trauma.
2) Prophylaxis for rebleeding from Intracranial aneurysm
3) As adjunctive therapy in hemophilia “added to something”
4) To stop bleeding caused by toxicity of fibrinolytic drugs
Why should hypertension be treated even if it was asymptomatic?
a) Damage to the vascular epithelium, paving the path for atherosclerosis, IHD, or nephropathy due to high intra-glomerular pressure
b) Increased load on heart due to high BP can cause CHF
ارتفاع الضغط حتى لو مش مسبب أعراض لكن ممكن يؤدي لتصلب
الشرايين ومشاكل في الكلية
What are the types of hypertension?
- According to the cause:
- Essential hypertension. “Primary (90%)”
- Secondary hypertension
According to the degree:
- Normal blood pressure ≤120 ≤80
- Stage 1 Hypertension 140–159 90–99
- Stage 2 Hypertension 160–179 100–109
- Stage 3 Hypertension ≥180 ≥110
- Isolated systolic hypertension>140 <90
“ISH respond more to CCBs”
“More than stage 3 —-> hypertensive emergency”
What is essential hypertension?
- A disorder of unknown origin affecting the blood pressure regulating mechanisms
What is secondary hypertension?
- Secondary to other disease processes
What is the target blood pressure for hypertensive patients?
- For most patients, the goal of therapy is to maintain BP < 140/90 .
- In patients with DM or chronic kidney disease, BP should be < 130/80
What does blood pressure equals?
- Blood Pressure = (CO) X (PVR)
How is blood pressure physiologically maintained?
- Physiologically BP is maintained by
1) Arterioles
2) post capillary venules
3) Heart
4) Kidney (volume of intravascular fluid) - Baroreflex and renin-angiotensin- aldosterone system regulates the above 4 sites
- Local agents like Nitric oxide
What is abnormal about baroreflex and Renal blood volume control system in hypertensive patient?
- Baroreflex and renal blood-volume control system set at higher level
How do all antihypertensive drugs work?
- All antihypertensives act via interfering with normal mechanisms.
How is hypertension generally treated?
1) Non-drug therapy or life style modification
2) Anti-hypertensive drugs
What is non-drug therapy of hypertension?
1) Non-drug therapy or life style modification:
- Sodium restriction and potassium and Mg supplementation.
- Stop smoking and avoid stress.
- Exercise and Weight reduction of obese patients.
Control of risk factors: e.g. DM, hyperlipidemia, and obesity. - Avoid drugs that ↑ BP e.g.: sympathomimetics, sodium-containing drugs, oral contraceptives, corticosteroids.
- Patients failing to normalize BP after 2 weeks of nonpharmacological therapy should be considered for drug treatment in addition to non drug therapy
What are antihypertensive drugs?
First choice groups (commonly used drugs):
- ACEIs
- Beta-blockers “2nd Line”
- Calcium blockers
- Diuretics
Second choice groups (used in special cases):
- α1- blockers: prazosin.
- Combined α and β-blockers: labetalol.
- Adrenergic neuron blockers: α-methyldopa.
- Vasodilators: hydralazine and diazoxide.
- Central α2 stimulants: clonidine.
- Dopamine agonists: fenoldopam.
Should RAAS be inhibited?
- Inhibition of RAAS will correct hypertension but also will ↓ GFR and aggravate RF if renal ischemia was grave (S. creatinine is > 3 mg/dl).
- So, if S. creatinine is up to 3 mg/dl (mild renal impairment) → you can safely block RAAS.
- If creatinine>3 mg/dl (severe renal impairment) → blocking RAAS will aggravate RF.
what is the classification of ACE inhibitors?
- SH-Containing drugs: Captopril
SH group may be responsible partially for immunological side effects “ATSL” e.g. angioedema, taste changes, skin rash and leukopenia.
- Non SH-Containing drugs: ✓ Enalarpril ✓ fosinopril ✓ lisinopril ✓ benazepril ✓ ramipril
“FELRB”
What is the mechanism of action of ACE inhibitors?
- They inhibit Ang-converting enzyme leading to Inhibition of Ang-II formation.
- Also they Prevent degradation of bradykinin which is a potent VD.
- ACEIs have direct arterio-veno dilator effects.
What are the pharmacological effects of ACE inhibitors?
1) They ↓ BP mainly by decreasing peripheral resistance
2) In presence of CHF, they ↑ COP due to reduction of both venous return (preload), and systemic BP (afterload).
3) They prevent cardiac remodeling “after MI”
What are the therapeutic uses of ACE inhibitors?
1) Systemic hypertension
2) Prevent LV remodeling after acute MI
3) Congestive heart failure (CHF)
4) Diabetic nephropathy & microalbuminuria
How do ACE inhibitors treat diabetic nephropathy and microalbuminuria?
- They ↓ renal changes complicating diabetic nephropathy (mesangial cell apoptosis, proliferation, and collagen synthesis)
- thus reducing microalbuminuria (provided that renal impairment is not grave).
What are the adverse effects of ACE inhibitors?
“No reflex tachycardia”
1) Dry Cough (the most common)
2) Angioedema (edema of the face and throat)
3) Aggravation of Proteinuria in patients with significant renal failure.
4) Taste changes
5) Orthostatic (First dose) hypotension
6) Teratogenesis (fetal pulmonary hypoplasia)
7) Skin rash.
8) Increased K+(hyperkalemia) due to ↓aldosterone release. “Should be used with K losing diuretics”
“AOT ATSL DryK”
What are the precautions that should be followed while using ACE inhibitors?
- Start with small dose at bedtime.
- Frequent monitoring of kidney functions (S. creatinine) and potassium levels one week after treatment and then every 3 months.
- Avoid use of K+ sparing diuretics.
What are the contraindications of ACE inhibitors?
1) Hypotension: when systolic BP is less than 95 mm Hg.
2) Severe renal failure or bilateral renal artery stenosis (SCr> 3 mg/dl).
3) Pregnancy and lactation.
4) Hyperkalemia.
5) Neutropenia, thrombocytopenia, or severe anemia.
“Suppresses BM”
6) Immune problems.
What are examples of ARBs?
Losartan - Valsartan
What is the mechanism of action of ARBs?
- They selectively block AT1 receptors.
How do ARBs have more efficacy than ACE inhibitors?
- ACE inhibitors are Less effective because other enzymes rather than ACE can convert Ang-I into Ang-II
- ARBs are More effective because it blocks AT-1 receptor, the final station responsible for Ang-II effects.
Is cough and angioedema common with ARBs?
- Less frequent (they do not↑bradykinins)