Pharma Flashcards
Give 3 reasons why someone may make a prescribing errors
- Loss of attention due to exhaustion
- Inappropriate training
- Illiterate hand writing
Define pharmacokinetics
-Study of the movement of a drug into and out of the body ie what the body does to the drug
Define pharmacodynamics
-Study of the drug effect and mechanism of action oe what the drug does to the body
Define pharmacogenetics. Give an example
- The effect of genetic variability on the pharmacokinetics or pharmacodynamics of a drug on an individual
- CYP450 enzymes have genetic variation within the population eg 2D6 and thus some people will not react or over react to a drug which is metabolised by this enzyme eg codeine
Give some factors which may effect the pharacokinetics of a drug
- Obesity
- Alcohol consumption
- Other medications
- Liver and renal function
- Albumin concentration
What is bioavailability of a drug? How do you calclulate it? Give some factors which affect bioavailability
- The fraction of a dose which finds its way into the circulation unchanged
- [AUC Oral] plasma/[AUC IV]plasma
- Route of administration, age, lipid solubility of drug, absorption of drug, first pass metabolism
What is first pass metabolism?
-The metabolism of a drug which occurs before it reaches the systemic circulation. Includes metabolism in the gut lumen by gastric acid/enzymes, gut wall by absorption and the liver
Broadly describe the 2 phases of drug metabolism in the liver
- Can either enter phase I or go straight into phase II
- Phase I involves cyp 450 and is a oxidation or reduction reaction which usually inactivaes the drug
- Phase II is a conjugation reaction with glucaronide, glutathione, sulphate which makes the drug water soluble so it can be eliminated
What are the two key factors which affect drug distribution and how do they do this?
- Protein binding -> Unbound drugs are able to bind to receptors and pass across cell membranes and have a pharmacological affect. Bound drugs remain in the circulation, therefore if a drug is highly bound the distribution will be less
- Volume of distribution -> a hypothetical measure of instantaneous distribution of drugs into available body compartments. If there is a low volume of distribution it means that the drug will be at high concentration in the body compartments which it can dissolve in
If there was a change in protein binding eg drug interactions, what properties of certain drugs would make you concerned?
- If a drug is highly bound -> displacement would rapidly increase the concentration of active drug
- If there was a low volume of distribution -> means the drug is in high conc in the places it is. displacing the drug from protein binding would raise the concentration more
- If the drug had a narrow therapeutic window because displacement could push the drug to toxic levels
Give 3 things which may affect protein binding
- Hypoalbuminaemia
- Pregnancy
- renal failure
- Displacement by other drugs
What factors have an effect on volume of distribution?
- Lipid solubility
- Regional blood flow
- Specific receptor sites in tissues
- Active transport
- Drug interactions
What is a pro-drug?
-A drug which is inactive when administered and becomes activated by the body eg codeine to morphine
Name some CYP inhibitors. What affect do inhibitors have on metabolism?
- Grapefruit juice (simvastatin)
- Omeprazole
- Anti-fungals
- Disulfram
- Erythromycin
- Valproate
- Isoniazid
- Cimetidine/Ciprofloxin
- Ethanol (acute)
- Sulphonamides
- Decrease metabolism of drugs prolonging the effects
Name some CYP inducers. What affect do inducers have on metabolism?
- Phenytoin
- Carbamazepine
- Cranberry Juice (warfarin)
- Rifampicin
- Alcohol (chronic)
- Barbituates
- St Johns Wort/Sulphonylureas
- Induce the production of the enzymes to increase metabolism of drugs and thus decrease their effects
What 3 processes determine the renal excretion of drugs? What is the relationship between clearance and half life?
- Glomerular filtration
- Passive tubular resorption
- Active secretion
- The lower the clearance (GFR) the longer the half life
What is first order and zero order kinetics? Why do most drugs exhibit zero order kinetics at high doses?
- 1st order = rate of elimination is proportional to drug level and a constant fraction is eliminated -> half life can be calculated
- Zero order= rate of elimination is constant regardless of drug level. half life not easily calculated
- Enzymes and receptors become saturated
Why does digoxin need a loading dose? Why does renal failure affect its toxicity?
- It has a long half life and steady state would take 3-5 half lives and you need rapid affect
- In renal failure there is less excretion of digoxin meaning that the drug will remain at toxic levels for longer and the same dose may reach toxic levels as that in a normal kidney
Describe the metabolism of paracetamol at therapeutic and toxic doses
What is the treatment for paracetamol overdose?
- Therapeutic -> 90% Paracetamol enters phase II metabolism and excreted, 10% enters phase II and converted to NAPQI but quickly undergoes conjugation with glutathione and inactivated
- Toxic -> Phase II saturated so much higher conc enters phase I metabolism. Produced large amounts of NAPQI and not enough glutathione to reduce so oxidative damage to the liver
- Activated charcoal within 1 hour
- N-acetylcysteine
How do competitive antagonist change the dose response curve? How is this over come?
- Keeps the same shape but shifts it to the right
- Adding more agonist (its surmountable)
How do non-competitive antagonist change the dose response curve? How is this over come?
- You get the same shape but the total response is decreased
- It cannot as it alters the conformational shape of target
What is the difference between drug selectivity and drug specificity?
- Selectivity refers to how well a drug binds to one group of receptor targets without binding to other targets and producing undesirable effect
- Specificity refers to how well the drug binds to a receptor subtype allowing it to be organ specific
What is affinity? What pharmacological term is used to measure affinity and how is it interpreted?
- A measure of the tendancy of a ligand to bind to its target
- Kd -> The lower the Kd the higher the affinity
What is efficacy? What is potency?
- The abolity of a drug to be able to activate the receptor and produce a response once it is bound
- Potency is how much of the drug is needed to generate a response taking into account affinity and efficacy
What is the therapeutic window? How is it calculated?
Give 3 drugs with a narrow therapeutic window
- The range of doses which can effectively treat a condition whilst still remaining safe. It is between the lowest concentrations which cause the desired affect and lowest concentrations causing adverse effects
- EC50-> TD50
- Warfarin, digoxin and gentamicin
How can drug interactions be caused during the absorption of a drug?
-Something may prevent the drug being absorbed due to inducible/inhibitable active transporters in the gut
Name some drugs which prolong the QT interval
- Cocaine
- Haloperidol
- Erythromycin
- Amiodarone
- Tricyclic antidepressants
How can renal disease affect the pharmacodynamics/kinetics of drugs?
- Decreased clearance
- Disturbances in electrolytes may predispose to toxicity eg digoxin and hypokalaemia
- Nephrotoxins will further damage the kidney
How can hepatic disease affect the pharmacodynamics/kinetics of drugs?
- Decreased albumin production affects protein binding
- Decreased CYP450 production will change metabolism of drugs
- Reduced hepatic clearance of drugs
How can cardiac disease affect the pharmacodynamics/kinetics of drugs?
- Excessive response to hypotensive agents
- Reduced organ perfusion may lead to reduced hepatic flow and clearance and reduced renal flow and clearance
What is an adverse drug reaction? Give some risk factors for ADRs
- An unwanted or harmful reaction which occurs after administration of drugs and is suspected or known to be from the drugs
- Reckless prescribing, extremes of age, unknown allergies,co-morbidities, narrow therapeutic index
Give some causes of variability of individuals to a drug
- Pharmacogenetics
- Weight
- Age and sex
- Health condition
- Placebo effect
- Route of admission
- Drug interactions
Describe the first step in treating type 2 diabetes
-Diet and lifestyle eg reduce calorie intake in overweight, decreased saturated fat intake, limit salt intake, limit alcohol intake, stop smoking, exercise
What type of drug is metformin? What is its MOA? How is it eliminated? List some side effects
- Biguanide
- Increases insulin receptor sensitivity in muscle and adipose and inhibits hepatic gluconeogenesis
- Completely renally excreted (toxicity risk in renal failure)
- Diarrhoea, cough, muscle cramping
Name a sulphonylurea. What is its MOA? Give some adverse affects
- Gliclazide
- Stimulates pancreatic B cells to produce insulin by causing closure of ATP-sensitive K-channel leading to depolarisation and influx of Ca causing insulin release
- Hypoglycaemia and weight gain
Name some metglitinides. What is its MOA? Give some adverse effects. What is the difference between metglinides and sulphonylureas?
- Repaglinide/Nateglinide
- Rapid acting insulin secretagogues which work on ATP-sensitive K channel at distinct site from sulphonylureas
- Metglinides are rapid acting and have shorter halflives than SU
Name a thiazolidinedione. What is the MOA? Give some adverse effects
- Pioglitazone
- Insulin sensitiser by stimulating PPAR-g (peroxisome proliferator-activated receptor gamma) which regulates adipose, muscle and liver gene expression of insulin receptors. Causes increased glucose utilisation and decreased gluconeogenesis
- Weight gain, oedema, bladder cancer
Name a GLP-1 agonist. What is its MOA?
- Exanatide
- Agonist of glucose-like-peptide 1 which self-regulates blood glucose levels by promoting satiety, enhances insulin secretion, reducing hepatic gluconeogenesis
Name a DPP4 inhibitor. What is the MOA?
- Sitagliptin
- Inhibits DPP4. DPP4 usually breaks down incretins. Incretins are gut hormones which increase b-cell secretion of insulin promoting glucose utilisation and decrease hepatic gluconeogenesis
Name an a glucosidase inhibitor. What is its MOA. Gove some adverse effects
- acarbose
- Inhibits a glucosidase activity in the gut which delays glucose absorbtion into the blood
- Flatulence and diarrhoea
How do SGLT2 inibitors work? Give some adverse effects
- Prevent glucose reabsorption in the PCT causing increased glucose excretion
- Polyuria, dehydration, thrush, UTI
What is orlistat? Give some adverse effects
- Pancreatic and gastric lipase inhitior preventing breakdown and absorption of fats
- Foul smelling fatty diarrhoea
Give some adverse effects of exogenous insulin
- Hypoglycaemia
- Weight gain
- Lipid dystrophy
Briefly describe the main roles of insulin
- Stimulates uptake of glucose into liver, muscle and adipose tissue
- Decreases hepatic gluconeogenesis and inhibits glycogenolysis
- Promotes uptake of fats and inhibits lipolysis
Describe a typical insulin regime
- Long acting basal insulin
- Short acting insulin at meal times
How is insulin genetically engineered?
- Human insulin gene inserted into plasmid
- Transfected into bacterium
- Bacterium produces insulin
How are sex steroids transported? Where are they stored?
- Bound to Steroid Hormone Binding Globulin in the blood and albumin
- 1-2% is free and active
- Adipose tissue
How do steroid hormones exhibit their action?
- Lipophillic meaning they can diffuse across a PM
- Bind to corresponding cytoplasmic receptors which are translocated to nucleus or straight to nuclear receptors
- Cause an alteration in gene transcription to produce desired response
What is the common precursor to all sex steroids? What enzyme is involved in producing oestrogen from androgens?
- Cholesterol
- Aromatase
List some side effects of oestrogen, progesterone and testosterone
- Oestrogen = breast tenderness, water retention and thromboembolism
- Progesterone = Weight gain, acne, lack of concentration
- Testosterone = aggression, altered HDL:LDL ratio
Name a synthetic oestrogen and a synthetic progesterone
- Oestrogen = ethinyloestradiol
- Progesterone = Dydrogesterone, Desogestrel or medroxyprodgesterone
Why are OCPs of particular interest regarding drug interactions?
-Metabolised by CYP system meaning anything which induces or inhibits CYP enzymes can effect OCP
When is HRT prescribed? Which drugs are used in HRT?
- Hot fluses/sweats
- Vaginal dryness or dyspareunia
- Osteoporosis
- Oestradiol and Medroxyprogesterone
What are the main risks of HRT?
- Unopposed oestrogen increases the risk of endometrial and ovarian cancers
- Opposed oestrogen increases the risk of breast cancer
- Increased stroke risk
- Increased venous thromboembolism risk
What is clomiphene (clomid)? When is it used?
- A weak oestrogen (SERM)which blocks oestrogen receptors in ant pit, therefore inhibiting negative feedback and causing induction of ovulation via increased LH
- IVF
What is tamoxifen (novladex)?
- SERM which binds to ER in breast tissue and thus blocks stimulation of growth
- ER+ Br Ca
What is finasteride and when is it used?
-5a-reductase which is used in BPH
Why would an oral dose of POP need to be higher than a different route of administration?
-Subject to first pass metabolism and almost all progesterone metabolised in one pass
Why does oxidised LDL in the intima pro-atherogenic?
- Inhibits macrophage motility
- Induces T-cell activation and VSMC division/differentiation
- Toxic to endothelial cells
- Enhances platelet aggregation
Describe the pathway of cholesterol synthesis. Describe the MOA of statins. State some adverse drug reactions to statins
- HMG-coA -> mevaloate (hmg-coA reductase) -> cholesterol (synthase)
- Inhibit HMG-CoA reductase to prevent cholesterol synthesis in hepatocytes which increases clearance of LDL by receptor upregulation
- Increased transaminase levels, myopathy, GI complains, headaches and arthralgia
When are statins used?
- High cholesterol levels
- Decrease cardiovascular event risk
Name a fibric acid derivative. How do they work?When are they used? Give some side effects
- Bezafibrate
- PPAR-a agonist which increases the production of lipoprotein lipase. Increases the uptake and oxidation of fatty acids -> reduces triglyceride levels
- Hypertryglyceridemia
- GI upset, cholelithiasis, myositis
How does ezetimibe work? Give some ADRs
- Inhibits intestinal absorption of cholesterol causing decreased cholesterol delivery to liver so LDL receptor upregulation.
- Enterohepatically circulates so systemic exposure is little
- Headaches, abdo pain and diarrhoea
Why is it uncommon to use dual therapy with the lipid lowering drugs statins and fibrates?
-Increases risk for myopathy and rhabdomyolysis
Give some non-pharmacological advice to lower cholesterol
- Avoid too much red meat and eggs
- Eat foods with plant sterols such as flora proactive
- Take fish oil
- Get plenty of vitamin C
What is Rheumatoid Arthritis?
- Chronic systemic autoimmune related inflammatory condition characterised by symmetrical deforming peripheral polyarthritis via destruction of the synovium which eventually causes dissolution of the cartilage and bone. There is an imbalance between pro and anti-inflammatory mediators
- Onset often in young adult females
How is diagnosis of RA made?
-History + nodules in >1 joint+ serology for Rheumatoid Factor or Anti-CCP and CRP with a long duration of symptoms
What is the main difference in presentation between RA and OA?
-RA if worse on a moring and gets better with exercise whereas OA gets worse with use throughout the day
What is SLE? What serology in SLE?
- Autoimmine condition in shich autoantibodies are made against a variety of antigens. It is multisystemic, remitting and relapsing in nature with a variable presentation which is normally non-specific such as malaise, fatigue and myalgia but can include butterfly rash, renal disease and oral ulcers
- 95% ANA positive, also Anti-dsDNA +ve
Give 2 drugs which can cause lupus
- Isoniazid
- Phenytoin
What is vasculitis? Give some diseases in which it can be secondary to. Name vasculitis affecting large, medium and small vessels
- Systemic inflammation of the walls of BVs causing destruction or stenosis
- SLE, RA, HIV
- Large = Giant cell arteritis, Med = Polyarteritis Nodosa, Sml = Granulomatosis with polyangitis
Which antibody is often found in vasculitis?
-ANCA
Name 5 DMARDs
- Methotraxate
- Sulphasalazine
- Anti-TNF
- Rituximab
- Cyclophosphamide
Describe the MOA of corticosteroids. Give some ADRs of corticosteroids. What is the consequence of immediately stopping corticosteroid use. Give 3 diseases in which corticosteroids are used
- Anti-inflammatory by preventing IL1 and IL6 production by macrophages by inhibiting gene expression and Tcell activation
- Weight Gain, Striae, glucose intolerance, infection, osteoporosis (cushingoid)
- Adrenocortical insufficiency
- IBD, Ashtma, Arthritis
Describe the MOA of Azothioprine. When is azothioprine indicated? Give some ADRs.
- Incorporated into DNA synthesis which halts replication therefore can prevent proliferation of T and B cells.
- Organ Transplant, SLE/RA/IBD, leukaemia
- BM suppression, increased infection risk, hepatitis
What test must be performed before initiating azothioprine Tx and why?
- TPMT levels.
- It is the enzyme responsible for metabolism of Azothioprine into its active 6-mecerptopurine. The TPMT gene is polymorphic and decreased TPMT levels increases the risk of toxicity
Name 2 Calcineurin Inhibitors. What is their MOA. Give some ADRs
- Ciclosporin, tacrolimus
- Acts as an immunosuppressant by binding to calcineurin and preventing IL2 transcription
- Nephrotoxic, hypertension, gingival hyperplasia
When is cyclophoshamide indicated? What is its MOA? What is sigificant about its pharmacokinetics? Give some ADRs
- Lymphoma, leukaemia, wegeners
- An alkylating agent which cross links DNA inhibiting replication of fast proliferating cells so stops T/B cell replication
- Activated by CYP enzymes
- BM suppression + infection, hair loss, anaemia and infertility
Name an Anti-TNF. When is it indicated. Describe its MOA. Give some ADRs
- Infliximab
- IBD, RA, Psoariasis
- Decreases inflammation by decreasing cytokine production, particularly TNF-a, which decreases leukocyte chemotaxis, angiogenesis and decreases MMPs (joint destructin decreased in RA)
- TB reactivation, infection
When is Methotrexate indicated? What is its MOA? What is of interest about its pharmacokinetics?Give some ADRs
- RA, malignancy, IBD
- DHFR inhibitor to prevent the synthesis of purine and thymidine synthesis preventing replication of rapidly dividing cells. In RA MOA is unknown
- Very long halflife means weekly dosing. Requires toxicity monitoring
- Mucositis, BM suppression, hepatitis, cirrhosis, teratogenic