Drug Of The Day Flashcards
What is the drug class of amlodipine?
Dihydropyridine calcium channel blocker. Dihydropyridines are selective for peripheral vasculature smooth muscle and have little effect of the heart.
Common indications for amlodipine?
For reducing hypertension as cause peripheral vasodilation. Primary choice anti-hypertensive in low renin patients (African-Caribbean)
What is the mechanism of action of amlodipine?
CCBs target calcium initiated smooth muscle contraction. Interacts with alpha-1 subunit of VOCC in the membrane of vascular smooth muscle cells. Has little action of VOCC of cardiac myocytes.
Important adverse drug effects of amlodipine?
Ankle swelling, flushing, headaches due to vasodilation
May get palpitations (compensatory tachycardia - this is more likely in CCBs that have a greater chronotropic affect.
Important drug-drug interactions of amlodipine?
Amlodipine interacts with simvastatin, reducing the metabolism of the statin and maintaining its levels in the body. Need to reduce dose of simvastatin if taken together.
What is the drug class of losartan?
Losartan is an angiotensin II receptor blocker (ARB/AT1 - receptor blocker)
What are common indications for losartan?
To reduce blood pressure in hypertension, less effective in low renin patients (African/Caribbean)
Most effective drug at treating hypertension due to excessive activation of RAAS.
What is the mechanism of action of losartan?
Act as antagonists of angiotensin 2 at AT1 receptors, stopping vasoconstriction. Also stops the stimulation of aldosterone release from the adrenal glands and therefore reduces circulating fluid volume, water reabsorption through the effects of ADH and feelings of thirst. Only act by decreasing the effect of AT2 - no effect on bradykinin.
Important adverse drug effects of losartan?
Hypotension, hyperkalaemia due to decreased aldosterone, cause of worsen renal failure
important drug-drug interactions of losartan?
Drugs that increase potassium (spirolactone)
NSAIDS
What class of drug is indapamide?
Thiazide like diuretic
What are common indications for indapamide?
Hypertension
Hyperkalaemia
Hypocalcaemia
-useful over CCB in oedema
What is the mechanism of action of indapamide?
Inhibit the ;a/Cl co-transporter in the DCT. Decrease sodium and water reabsorption but RAAS compensates over time. Long term affects on sensitivity of vascular smooth muscles to vasoconstrictors (calcium/noradrenaline).
Important adverse drug reactions of indapamide?
Hypokalaemia Hyponatraemia Hyperuricaemia (gout) Arrhythmia Increased glucose Increased cholesterol and triglycerides
Important drug-drug interactions of indapamide?
NSAIDS
Potassium lowering drugs such as loop diuretics.
When used with beta blockers glucose reabsorption increased.
Why is it recommended to take indapamide first thing in the morning and not before bed?
As thiazide like diuretics act within one or two hours, rapid diuresis often occurs in the first few doses but is less noticeable with continued treatment. Taken in the morning to minimise nocturia.
What drug class is Atorvastatin?
A statin
What are the common indications for atorvastatin?
CVD prevention
- Primary prevention- 20mg of atorvastatin once daily if there is a 10 year CVD risk of greater than 10% using QRISK
- secondary prevention - 80mg atorvastatin once daily
LDL cholesterol lowering
What is the mechanism of action for atorvastatin?
Statins have competitive inhibition of HMG-CoA reductase (rate controlling enzyme in the HMG-CoA to mevalonate pathway.)
Contributes to the upregulation of hepatic LDL receptors, increasing the clearance of LDL.
What are the adverse drug reactions of atorvastatin?
GI disruption, nausea, headache
Myalgia
Rhabdomyolysis
Increased liver enzymes
What are the important drug-drug interactions of atorvastatin?
CYP 3A4 important – amiodarone, diltiazem, macrolides - increases [plasma] statin
Amlodipine (CCB) also increases [plasma] statin
What is the difference between high dose and low dose atorvastatin offered to patients?
Low dose is used in primary prevention of CVD = 20mg of atorvastatin daily
High dose is used in secondary prevention of CVD when the patient has already had a major CVD event = 80mg of atorvastatin once daily.
What drug class is spironolactone?
A aldosterone (mineral corticoid ) receptor antagonist.
What are the common indications of spironolactone?
As step 4 in treating hypertension is step 3 (treatment with ACEi or ARB + CCB + Thiazide like diuretic) hasn’t corrected hypertension
What is the mechanism of action of spironolactone?
Blocks the aldosterone receptor in the collecting duct. ENAC channels and ROMK channels are not expressed. More sodium and therefore water lost in urine. Spironolactone is not highly selective and may affect other steroid receptors ( such as the testosterone receptor ) and cause adverse effects.
What are the adverse drug reactions of spironolactone?
Hyperkalaemia
Gynecomastia
What are the important drug-drug interactions of spironolactone?
Drugs that increase potassium levels
Pregnancy
Why is adherence of spironolactone a particular challenge, especially in men?
As can block the testosterone receptor causing challenging symptoms such as gynaecomastia and symptoms associated with androgen deficiency such as decreased sex drive/erectile dysfunction/loss of body hair.
What drug class is metformin?
Biguanide
What are the common indications of metformin?
First line choice for treatment of T2DM (HbA1c over 48mmol/mol)
What is the mechanism of action of metformin?
Decrease hepatic glucose production by inhibiting gluconeogenesis. Some gluconeogenic activity remains so hypoglycaemia risk is reduced.
Suppresses appetite so limits weight gain
What are the adverse effects of metformin?
GI upset, nausea, vomiting, diarrhoea
What are the important drug-drug interactions of metformin?
ACEi, diuretics, NSAIDs - drugs that impair renal function.
Loop and thiazide diuretics as they increase glucose reabsorption so reduce the action of metformin
What are the potential side effects of weight and glycaemic control when taking metformin?
Most treatments of T2DM result in weight gain due to the promotion of anabolic activity. As metformin suppresses appetite it limits weight gain.
Risk of hypoglycaemia is small as only partially inhibits gluconeogenesis in the liver.
What drug class is sitagliptin?
Dipeptidyl peptidase-4 inhibitors (DPP-4 inhibitors / gliptins )
What are the indications of sitagliptin?
Used is combination with metformin in the treatment of T2DM.
What is the mechanism of action of sitagliptin?
Prevents the degradation of incretin (GLP-1). Increases the plasma GLP-1 levels. Glucose dependant (to release the incretins in the first place) so postprandial action. Does not stimulate insulin release at normal blood glucose levels so have a lower hypoglycaemic risk than other treatments.
What are the common adverse affects of sitagliptin?
GI upset, small pancreatitis risk
What are the important drug-drug interactions of sitagliptin?
Other hypoglycaemic agents
Drugs that increase plasma glucose as action oppose gliptin action.
Thiazide like and loop diuretics.
How does sitagliptins mechanism of action differ from that of GLP-1 receptor agonist/incretin mimetics?
Both exert their action through the action of GLP-1 receptors.
Sitagliptin increases the amount of endogenous GLP-1 by stopping its degradation.
Incretin mimetics increase glucose dependant synthesis of insulin secretion. Act by activating the GLP-1 receptor
What drug class is gliclazide?
Sulfonylurea
What are the indication of gliclazide?
Used with a combination of other agents (metformin) in the treatment of T2DM
Used as a first line option for treatment of T2DM is metformin is contraindicated.
What is the mechanism of action of gliclazide?
Stimulate B-cell pancreatic insulin secretion by blocking the ATP-dependant K+ channels, causing membrane depolarisation.
What are the adverse effects of gliclazide?
Mild GI upset, nausea, vomiting, diarrhoea, hypoglycaemia (works at low glucose)
Weight gain through anabolic effects of insulin.
What are the important drug-drug interactions of gliclazide?
Other hypoglycaemic agents
Loop and thiazide like diuretics that increase glucose levels and so reduce the SU action
How does the action of gliclazide differ from some of the other hypoglycaemic drug classes?
Other hypoglycaemic drug classes such as biguanides and thiazolidinediones affect storage mechanisms in the body to increase anabolic or decrease catabolic reactions. Gliclazide acts by promoting insulin release, which is only possible if there is some residual pancreatic function.
What is the drug class of clopidogrel?
ADP receptor antagonist
What are the indication of clopidogrel?
Used for a wide variety of presentations where anti platelet is needed.
Mono therapy where aspirin is contraindicated.
NSTEMI patients for 3 months
STEMI patient for up to 4 weeks.
Ischaemic stroke and TIA long term secondary prevention.
What is the mechanism of action of clopidogrel?
When endothelium is damaged it releases ADP, which is detected by the P2Y12 receptor causing activation of GPIIb/IIIa receptors which results in platelet aggregation. Clopidogrel is an irreversible inhibitor of the P2Y12 receptors and stops this platelet aggregation mediated by ADP by blocking the ADP receptor
What are the adverse effects of clopidogrel?
Bleeding! GI upset - dyspepsia and diarrhoea
Thrombocytopenia
What are the important drug-drug interactions of clopidogrel?
Clopidogrel requires CYPs for activation as it is a prodrug.
CYP inhibitors - omeprazole, ciprofloxacin, erythromycin, some SSRIs need to consider use of other PPIs with clopidogrel
Caution when co prescribed with other antiplatelet and anticoagulant agents or NSAIDs – increased bleeding risk
What drug class is amiodarone?
A class 3 antiarrhythmic
What is the common indications for amiodarone?
Wide spectrum; effective for most arrhythmias e.g WPW, VT, AF, chronic re-entrant NCT, ectopic beats
What is the mechanism of action of amiodarone?
Block the K+ channels, preventing efflux of potassium from cardiac myocytes. Membrane takes longer to repolarise and action potential duration increases. Prolonged refractory period and APD.
What are the adverse effects of amiodarone?
Pulmonary fibrosis (SoB) Hepatic injury Increase LDL cholesterol (treat with statins) Thyroid disease. Photosensitivity Optic neuritis
What are the important drug drug interactions of amiodarone?
Reduce dose of digoxin
Monitor warfarin more closely
Why is amiodarone contraindicated in thyroid disease?
Amiodarone has a high iodine content and therefore can influence the action of the thyroid causing hyperthyroidism or hypothyroidism
What is the drug class of verapamil?
CCB
Non- dihydropyridine
Phenylalkylamines - class IV anti-arrhythmic agent
What are the common indications of verapamil?
Control ventricles during SVT Convert SVT (re-entry around the AV)
What is the mechanism of action of verapamil?
Calcium channel blocker that are more selective for myocytes than peripheral vasculature smooth muscle.
Decreases the slope of Phase 0 by decreasing inward calcium currents.
Slow conduction through the AV
Prolongs the AP and effective refractory period
Negative chronotropic and inotropic effects.
What are the adverse effects of verapamil?
Caution when partial AV block and cardiac failure present
Caution when hypotension, decreased CO, or sick sinus.
GI problems - constipation.
Bradycardia.
What are the portent drug-drug interactions of verapamil?
Beta blockers - can cause asystole
Other Antihypertensive and antiarrhythmic agents
How does the pharmadynamics of verapamil differ to other drugs in the broad class which dictates its primary therapeutic uses?
Verapamil is a calcium channel blocker, much like amlodipine. Different classes of CCB interact with different sites on the alpha1 subunit of the VOCC. They also have different selectivity for vascular smooth muscle or myocardium.
Verapamil - a non-dihydropyridine - is more selective for myocardium, having negative chronotropic and inotropic effects
Amlodipine is a dihydropyridine and is more selective for peripheral vasculature, decreasing TPR in hypertension.
What drug class is aspirin?
Cyclo-oxygenase inhibitor
What are the common indications of aspirin?
Atrial fibrillation S before considering anticoagulants
Secondary prevention of stroke and TIA
Secondary prevention of acute coronary syndromes (ACS)
Post primary Percutaneous coronary intervention and stent to reduce ischaemic complications
Often co-prescribed with other anti platelet agents
NSTEMI/STEMI loading dose
What is the mechanism of action of aspirin?
Inhibits the COX-1 enzyme. Stops COX-1 mediated production of thromboxane A2 from arachidonic acid.
TXA2 is a powerful platelet aggregating agent and by reducing its production aspirin irreversibly reduces platelet aggregation
What are the adverse effects of aspirin?
GI irritation GI bleeding (peptic ulcer) Haemorrhage (stroke) Hypersensitivity Reye’s syndrome in children ( brain and liver damage)
How does the pharmacodynamics at low doses of aspirin affect the therapeutic effect this drug has?
Lower doses (75mg) act to inhibit COX-1 enzyme to have an anti platelet aggregation affect. At higher doses aspirin can inhibit endothelial prostacyclin (PGI2) which acts to inhibit platelet aggregation. Therefore at higher doses it has less use as an anti platelet and more use as an NSAID through its down regulation of prostanoid synthesis
What are the important drug - drug interactions of aspirin?
Other anti platelets and anticoagulants (additive/synergistic action)
What drug class is flecainide?
A class IC Antiarrythmic
What are the common indications of flecainide?
Wide spectrum use for Arrhythmias
Used for supraventricular Arrhythmias (fibrillation and flutter)
Premature ventricular contractions
Wolff-Parkinson White syndrome
What is the mechanism of action of flecainide?
Class 1 antiarrhythmic drugs block the sodium channel and therefore decrease the depolarisation of cardiac myocytes.
Results in very slow binding offset of kinetics
Slows conduction in tissue
Slows the automaticity by increasing the threshold
Increases the action potential duration
Increases the refractory period especially in rapidly depolarising atrial tissue
What are the adverse effects of flecainide?
Pro-arrhythmia
Increase ventricular response to supraventricular Arrhythmias causing a flecainide flutter.
GI effects
What are the important drug-drug interactions of flecainide?
Used with bisoprolol commonly to treat AF
Use with caution with other antiarrythmic drugs
What drug class is celecoxib?
A selective COX-2 inhibitor
What are the primary indications for celecoxib?
Can be useful when monitored in severe osteo and RA for longer term treatment.
What is the mechanism of action of celecoxib?
Selectively inhibits the COX-2 enzyme. Which in turn causes less production of prostacyclin and prostaglandins. As COX-1 is not inhibited some prostaglandins and thromboxane A2 are still produced, meaning less GI ADR occur.
What are the adverse drug reactions of celecoxib?
Risk of MI
Renal ARDs = decreased GFR and renal blood flow. More likely to occur in underlying CKD or HF
hypernatraemia resulting in increased BP
GI ARDs = Dyspepsia, nausea, peptic ulcers, bleeding and perforations. Less risk than NSAIDs that are not selective to COX-2.
What are the drug-drug interactions of celecoxib?
Aspirin
Glucocorticoid steroids
Anticoagulants
ACEi, ARBs, Diuretics
What drug class is azathioprine?
Immunosuppressant
What is the common indication of azathioprine?
Previously used following transplantation
Used to treat RA, granulomatosis with polyangiitis, Crohn’s disease, UC, SLE, vasculitis, atopic dermatitis and bullous skin disease.
Also used as a steroid sparing drug
What is the mechanism of action of azathioprine?
Cleaved to 6-MP
6-MP is then metabolised by TPMT to several other metabolites
TIMP, an active metabolite of 6-MP decreases DNA and RNA synthesis
This therefore decreases cell replication rate.
What are the common adverse effects of azathioprine?
Bone marrow suppression -monitor FBC
Increased risk of malignancy, especially in transplanted patients
Increased risk of infection
Hepatitis, monitor LFT.
What are the common drug drug interactions of azathioprine?
ACEi - increases risk of anaemia and leukopenia.
Why does the prescribing risks of azathioprine vary between individuals?
As the gene that encodes for the enzyme TPMT is highly polymorphic. This means individuals vary markedly in TPMT activity.In individuals with low TPMT levels, there is an increased risk of myelosuppression
What drug class is salbutamol?
Fast short acting Beta2 agonist
What are the common indications of salbutamol?
Symptom relief of asthma through reversal of bronchoconstriction. Only used p.r.n.
Nebuliser salbutamol and/or ipratropium prescribed in acute exacerbation of COPD
What is the mechanism of action of salbutamol?
Binds to B2 receptors in the smooth muscle of the airways. Causes release of the alphaS subunit which stimulates adenylyl cyclase to synthesise cAMP from ATP. cAMP results in the stimulation of phosphokinase A which triggers bronchial smooth muscle relaxation.
Also increase mucus clearance action of cilia.
What are the common adverse effects of salbutamol?
Adrenergic - fight or flight effects by acting on the beta1 receptors in the kidney heart and adipose.
Cause tachycardia, palpatations, anxiety and tremor. Increases glycogenolysis and renin production in the kidney.
What are the common drug-drug reactions of salbutamol?
Beta blocker aswould cause functional antagonism of salbutamol.
What distinguishes salbutamol from others in the broader class?
Salbutamol is a fast acting short lasting beta 2 agonist. This means that it is used for symptom relief during asthma exacerbation.
What drug class is morphine?
Strong agonist opioid
What are the common indications of morphine?
Commonly used for analgesia. Used in palliative prescribing to relieve pain and shortness of breath
What is the mechanism of action of morphine?
Strong affinity to mu opioid receptors found in the brainstem and thalamus, causing complete activation.
On binding morphine leads to a decrease in cAMP production which causes an efflux of potassium and hyperpolarisation of the membrane.
This decreases the release of substance P and GABA which decreases the pain response aswell as increasing dopamine release.
What are the adverse affects of morphine?
Respiratory depression Emesis GI tract problems (constipation) CVs effects Miosis Histamine release by activation of mast cells - caution in asthmatics
What are the drug-drug interactions of morphine?
Avoid with other opioids as overdose is common
Why might morphine be used over other drugs in the same class?
On balance morphine gives good analgesia, better than codeine for most but fentanyl is used in high pain settings particularly post operatively and fentanyl patches can be useful in some situations.
it’s less addictive than fentanyl and more potent than codeine
What drug class is fluticasone?
An inhaled corticosteroid
What are the common indications for fluticasone?
Prescribed as a regular preventer alongside a SABA in the first line treatment of asthma
What is the mechanism of action of fluticasone?
Corticosteroids modulate gene expression by causing gene activation resulting in upregulation of B2 receptors and anti-inflammatory mediators.
Also inhibit the release of arachidonic acid
Also causes gene repression and down regulation of inflammatory mediators, interleukins, chemokines, cytokines
What are the adverse drug reactions of fluticasone?
Local immunosuppressive action = candidiasis, hoarse voice
What are the drug-drug interactions of fluticasone?
Very few
Why are the ADR of fluticasone minimal?
As have very poor oral bioavailability and dont enter systemic circulation. Lipophillic side chain is added as a modification to slow the dissolution in aqueous bronchial fluid. Also has almost complete first pass metabolism
What drug class is omeprazole?
A proton pump inhibitor
What are the common indications for omeprazole?
GORD
Peptic ulcerations.
What is the mechanism of action of omeprazole?
Irreversibly inhibits the H+/K+ ATPase in gastric parietal cells. Stops acid secretion into the stomach.
What are the common drug-drug interactions of omeprazole?
Clopidogrel - reduced action as omeprazole is a CYP inhibitor
PPIs can increase the effects of warfarin and phenytoin - need to adjust dosage and monitor
What are the adverse affects associated with omeprazole?
GI disturbance - abdominal pain, constipation diarrhoea
Headache, dizziness
Drowsiness/confusion
Where might omeprazole be co prescribed with other drug classes?
Often prescribed alongside a NSAID or steroid as these drugs can cause damage to the stomach lining as they reduce the production of protective prostaglandins. Therefore omeprazole co prescribed to protect the stomach gastric cells by reducing the acid secretion.
What drug class is cyclizine?
A H1 receptor antagonist (acts on the vestibular nuclei)
What are the common indications for cyclizine?
Antiemetic
Motion sickness - esp. long plane journeys or as a passenger as have sedentary effect
Morning sickness
What is the mechanism of action of cyclizine?
Acts centrally on the vestibular nuclei to inhibit the histerminergic signals from the vestibular system to the Chemoreceptor trigger zone in the medulla.
What are the important drug drug interactions of cyclizine?
Certain antiarrhythmic s ( amiodarone, sotalol and flecainide) that increase the QT interval - risk of torsades de pointes.
Sedative psychiatric drugs
Anticholinergics
What are the common adverse drug reactions of cyclizine?
Sedation
Excitation
Antimuscarinic – dry mouth, constipation, urinary retention,
Cardiac toxicity (long QT interval)
What is the drug class of metoclopramide?
D2 receptor antagonist (antiemetic)
what are the common indications for metoclopramide?
to treat nausea and vomiting due to visceral afferents from the gut.
GORD
Ileus (lack of peristalsis)
what is the mechanism of action of metoclopramide?
D2 receptor is the main receptor in the chemoreceptor trigger zone in the medulla. stopping dopamine binding reduces activation of this area, and therefore emesis. Also dopamine acts to increase the acetylcholine at muscarinic receptors in the gut. This promotes gastric emptying by:
- increased tone at lower oesophageal sphincter so it closes
- increased tone and amplitude of gastric contractions
- decreased tone of pylorus so it opens
what are the contraindications of metoclopramide?
males - can cause galactorrhoea
in parkinsons do not prescribe as can cause parkinsonism features.
childran and young adults as extra-pyrimidal side effects more common in these groups
what are the drug drug interactions of metoclopramide?
antipsychotics - when co-prescribed with metoclopamide can increase risk of extra pyramidal side effects.
should not be used with dopaminergic agents for parkinsosn disease as would antagonise their effects.
what are the adverse drug reactions of metoclopramide?
galactorrhoea due to release of prolactin
extra-pyrimidal effects - dystonia and parkinsonism
what drug class is LMWH?
low molecular weight heparin
what are the common indications of LMWH?
prevention of venous thromboembolism perioperative prophylaxis pregnancy deep vein thrombosis pulmonary embolism acute coronary syndrome most indications to stop thrombus formation and thrombus growing
give some examples of LMWH?
dalteparin
enoxaparin
what is the mechanism of action of LMWH?
bind to the glycoprotein antithrombin. then selectively accelerates the interaction of antithrombin with factor Xa, inhibiting this factor within the coagulation cascade
what is the common adverse drug reactions of LMWH?
bruising and bleeding - intracranial, at site of injection, GI, epistaxis
heparin induced thrombocytopenia
hyperkalaemia - inhibition of aldosterone secretion
osteoporosis - rare long-term use
what are the contraindications of LMWH?
clotting disorders
renal impairment
recent surgery or trauma
what are the important drug drug interactions of LMWH?
other antithrombotic drugs
ACEi/ARB/spironolactone
how do heparins impact aldosterone secretion?
It is thought that heparin interacts in a way that reduces the number of receptors and affinity for them which results in a negative feedback. With withdrawal of heparin therapy this is reversible.
what are the differences between LMWH and UFH?
dose response: UFH have a non-linear elimination so response is unpredictable, LMWH are predictabel
bioavailability: UFH have variability bioavailabiliy s.c. of 30%, LMWH are more predictable at 90%
metabolism: UFH is dose dependent ( 1st and zero order kinetics). LMWH have fast liver excretion or slower renal excretion.
monitoring : UFH need monitoring with aPTT, generally no monitoring for LMWH
administration: UFH are i.v.i s.c., LMWH are s.c.
initiation: UFH need a loading bolus dose i.v, then i.v.i, LMWH are just bd/od
half life: UFH have a variable half life (30min low dose, 2hour high dose), LMWH is 2+ hours
Action: i.v.i. fast anticoagulation of UFH, LMWH are slower
use: UFH are used for moderate renal impairment and very fine control, LMWH are used for most situations.
what drug class is apixaban?
direct acting oral anticoagulant
how does the mechanism of action of the apixaban sub class differentiates it from the other sub classes of DOAC?
apixaban inhibit factox Xa of the coagulation cascade, and does not directly effect thrombin (factor IIa)
other DOACs such as dabigatran are instead selective direct competitive thrombin inhibitors, both circulating and thrombin bound to IIa. have no affect of factor Xa.
what are the common indications of apixaban?
prevention of thrombus formation
lower intracranial bleeding risk than warfarin
what is the mechanism of action of apixaban?
inhibit both free Xa and that bound to ATIII. do not directly effect thrombin. prevent the coagulation cascade.
what are the adverse side effects of apixaban?
bleeding
esp in GI bleed risk groups
what are the contraindications of apixaban?
contraindicated at very low creatinine clearance (<15mL/min)
little information on use in pregnancy and breastfeeding so avoid
what are the important drug interactions of apixaban?
affected by CYP inhibitors and inducers
- plasma concentration reduced by inducers ( carbemazepine/phenytoin/barbiturates)
- plasma concentration increased by inhibitors (macrolides)
what is the drug class of co-amoxiclav?
penicillin
what 2 drugs are in co-amoxiclav?
contains amoxicillin and clavulanic acid.
what are the common indications of co-amoxiclav?
bacterial meningitis bone and joint infections skin and soft tissue infections otitis media pneumonia UTI's STI's
what is the mechanism of action of co-amoxiclav?
amoxicillin is a penicillin antibiotic and therefore a beta lactam. Beta lactams act by interfering with the synthesis of the bacterial cell wall peptidoglycan. They bind to penicillin binding protein and inhibit the transpeptidation enzymes responsible for cross-linking peptidoglycans. the cell walls are weakened and unable to maintain an osmotic gradient, and results in cell swelling, lysis and death. Amoxicillin has the addition of an amino group to the side chain which increases activity against aerobic gram-negative bacteria, making it a broad spectrum antibiotic.
Clavulanic acid is a beta lactamase inhibitor, which allows amoxicillin to work on beta-lactamase producing bacteria (staphylococcus aureus)
what are the contraindications of co-amoxiclav?
used in caution with those at risk of c.difficile infection (hospital and elderly)
if patient has a history of a penicillin allergy
does of broad spectrum penicillins should be reduced in patients with severe renal impairment as can cause crystalluria
what are the adverse drug reactions of co-amoxiclav?
GI upset = nausea and vomiting
penicillin allergy presenting with a skin rash
what are the drug interactions of co-amoxiclav?
- Penicillins reduce renal excretion of methotrexate, increasing the risk interactionsof toxicity.
- Broad-spectrum penicillins can enhance the anticoagulant effect of warfarin by killing normal gut flora that synthesise vitamin K.
what drug class is carbamazepine?
anti-epileptic
sodium channel blocker
what are the common indications of carbamazepine?
bipolar disorder - prophylaxis
chronic pain - trigeminal neuralgia
epilepsy - first choice for focal seizures and for primary generalised seizures
what is the mechanism of action of carbamazepine?
inhibits neuronal sodium channels, stabilising resting membrane potentials and reducing excitability
what are the contraindications of carbamazepine?
pregnancy - associated with neural tube defects if exposed to in utero
antiepileptic hypersensitivity syndrome
caution in patients with hepatic renal or cardiac disease due to the increase risk of toxicity
what are the common ADRs associated with carbamazepine?
GI upset neurological effects such as dizziness and ataxia joint pain suicidal thoughts bone marrow failure antiepileptic hypersensitivity syndrome (severe skin reactions, fever, lymphadenopathy with systemic involvement) oedema hyponatraemia
what are the drug interactions of carbamazepine?
carbamazepine is a CYP450 inducer.
reduces the plasma concentration and efficacy of:
warfarin
oestrogens
progesterones
CYP450 inhibitors increase carbamazepines concentration and therefore its side effects (macrolides)
complex interactions with other antiepileptic drugs
efficacy reduced by drugs that lower the seizure threshold ( SSRIs, tricyclic antidepressants, antipsychotics, tramadol)
what is the drug class of sodium valproate?
anti-epileptic (sodium channel blocker)
what are the common indications of sodium valproate?
1st line for generalised epilepsies
bipolar disorder
what is the mechanism of action of sodium valproate?
blocking of sodium channels in the CNS slows the recovery of neurones from inactive to closed state. This reduces neuronal transmission. Also due to effects on GABAa receptor, resulting in increased brain content of GABA, one of the main CNS inhibitory neurotransmitters
what are some of the common adverse drug reactions of sodium valproate?
liver failure (thrombocytopenia) pancreatitis lethargy common to all anti-epileptics: tiredness and drowsiness nausea and vomiting mood changes and suicidal thoughts osteoporosis rashes
what are some of the contraindications of sodium valproate?
pregnancy
family planning female
breastfeeding
avoid prescribing to women of child bearing age
avoided in hepatic impairment and does reduction in renal impairment
what must be considered before giving sodium valproate to a female?
sodium valproate should not be prescribed to any woman of childbearing age unless they meet the conditions of a pregnancy prevention programme. need to be on contraceptive method as valproate is a major teratogen causing congenital malformations
why is co-careldopa a compound drug and how this helps achieve therapeutic benefit?
co-careldopa is a compound drug of levodopa and carbidopa. Carbidopa is a peripheral dopa decarboxylase inhibitor that works to decrease the amount of levodopa metabolised in the gut and peripheries and therefore increassing the concentration of levodopa reaching the CNS, also lowers the dose required and reduces the side effects
what is the drug class of co-carelodopa?
levodopa - dopaminergic drug
what are the common indications of co-careldopa?
treatment of Parkinsons
what is the mechanism of action of co-careldopa?
levodopa, a precursor of dopamine can cross the BBB to be metabolised in the CNS to increase the dopaminergic stimulation to the striatum in the basal ganglia. This causes more excitatory effects on the thalamus and therefore increases the excitatory input into the motor cortex. Carbidopa increases the effect of levodopa.
what is the contraindications of co-careldopa?
caution in elderly
in patients with existing cognitive or psychiatric disease
CVD as can cause hypotension
what are the common ADRs of co-careldopa?
nausea, drowsiness, confusion, hallucinations and hypotension
wearing off effect where the patients symptoms worsen at the end of the dosage interval causing dyskinesias
what are the common drug interactions of co-careldopa?
antipsychotics or metoclopramide as their effects on the dopamine receptors are contradictory
