Pharmacology Flashcards
What are the 2 most common electrolyte disturbances seen with thiazide diuretics?
Hyponatraemia
Hypokalaemia
Which drugs should not be given in combination with Verapamil due to negative inotropic effect?
Beta blockers
Quinidine
What is the mechanism of action of Ketamine?
non-competitive antagonism of the NMDA receptor Ca2+ channel pore
also inhibits NMDA receptor activity by interaction with the phenylcyclidine binding site
Co-administration of what type of drug can help reduce incidence of psychotic effects from ketamine?
Benzodiazepines
What are the 5 ECG changes seen in TCA overdose?
Sinus tachy Prolonged PR interval Broad QRS Prolonged QT Ventricular arrhythmias
Give 3 examples of antibiotics that interfere with cell wall synthesis?
Penicillins
Cephalosporins
Vancomycin
What is the leading cause of drug-induced angioedema in UK?
ACEi
Patients most commonly present with swelling of the lips, tongue, or face, although another presentation is episodic abdominal pain due to intestinal angioedema. Urticaria and itching are notably absent.
What are the 4 clotting factors inhibited by Warfarin?
What other 3 factors are also inhibited?
VIt K dependent clotting factors - 2, 7, 9, 10.
Protein C, Protein S, Protein Z
What are the antidotes for sulfonylurea poisoning?
Glucose
Octreotide
What dose of Amiodarone is used in VF/pVT arrest and how is it prepared?
300mg IV after 3rd shock
Diluted in 5% dextrose to volume of 20ml
What drug can be given in VF/pVT arrest if Amiodarone is unavailable?
Lidocaine, 1 mg/kg
do not give lidocaine if amiodarone has already been given.
What drug can be used to treat acute drug induced dystonic reactions?
Procyclidine - an anticholinergic
What is the mechanism of action of Enoxaparin?
Enoxaparin is a low molecular weight heparin (LMWH) that binds to and potentiates the inhibitory effect of antithrombin III in a similar manner to heparin. Antithrombin III forms a 1:1 complex with thrombin and inactivates it. The heparin-antithrombin III complex also inhibits factor Xa and some other proteases involved with clotting.
What drugs can be used in thyroid storm to block the release of thyroid hormones?
Potassium iodide
Why should Furosemide and SSRIs such as Citalopram not be prescribed together?
Increased risk of hyponatraemia and hypokalaemia, potentially increasing risk of Torsades de pointes
What is the MOA of thiazide diuretics?
Acts on NaCl co-transporter in DCT
What is the MOA of loop diuretics?
Acts on NaK2Cl co-transporter in ascending loop of Henle
What is the MOA of Adenosine?
Opens K+ channels in heart, slowing conduction in the AV node
What is the MOA of Amiodarone?
Blocks Na+ and K+ channels and beta-adrenoreceptors, prolonging phase 3 of cardiac action potential and slowing conduction at SA and AV nodes
What is the MOA of Verapamil?
Blocks Ca2+ channels in heart, slowing conduction in the AV node
Which anti-epileptic medication is most closely linked to cleft palate?
Phenytoin
What is a 1% solution?
1g per 100ml
What is the maximal safe dose of plain lidocaine?
3 mg/kg
When should Lidocaine not be used with Adrenaline?
In fingers, toes and nose (extremities) due to risk of vasoconstriction and tissue necrosis
Although lidocaine alone tends to cause vasodilation
What is the duration of lidocaine and half life?
Half life 1.5-2 hours
Duration of action when used alone is 30-60 mins
What is thought to be the MOA of paracetamol?
Paracetamol is thought to work by selectively inhibiting cyclo-oxygenase 3 (COX-3) receptors in the brain and spinal cord. COX-3 is responsible for the production of prostaglandins in these areas, which sensitizes free nerve endings to the chemical mediators of pain.
Therefore by selectively inhibiting COX-3 paracetamol effectively reduces pain sensation.
What is the MOA of Aspirin?
Aspirin irreversibly blocks cyclo-oygenase by covalently acetylating the cyclo-oxygenase active site in both COX-1 and COX-2
At low doses (75 mg per day) aspirin only inhibits COX-1, the enzyme responsible for making thromboxane A2, and therefore principally exhibits an anti-thrombotic effect.
At medium to high doses (500-5000 mg per day) aspirin inhibits both COX-1 and COX-2. COX-2 is responsible for the production of prostaglandins and therefore has an anti-inflammatory effect at these doses.
How does Propofol effect cardiac output?
Propofol produces a 15-25% decrease in blood pressure and systemic vascular resistance without a compensatory increase in heart rate. It is negatively inotropic and decreases cardiac output by approximately 20%.
List P450 enzyme inducers?
PC BRASS
P – Phenytoin C – Carbemazepine. B – Barbiturates R – Rifampicin A – Alcohol (chronic ingestion) S – Sulphonylureas S – Smoking
St John’s Wort
List P450 enzyme inhibitors?
MOCK DEVICES
M - Metronidazole
O – Omeprazole
C - Chloramphenicol
K - Ketoconazole
D – Disulfiram E – Erythromycin (And other macrolide antibiotics) V – Valproate (sodium valproate) I – Isoniazid C – Ciprofloxacin E – Ethanol (acute ingestion) S – Sulphonamides
Give 1 example of an antiemetic that works via antimuscarinic effect?
Hyoscine
Give 3 examples of antiemetics that work via antihistamine effect?
Cyclizine
Promethazine
Cinnarizine
Give 3 examples of antiemetics that work via anti dopamine effect?
Domperidone
Metoclopramide
Prochlorperazine
Give 2 examples of antiemetics that work via 5-HT3 receptor antagonism?
Ondansetron
Granisetron
Grey baby syndrome is caused by which antibiotic?
Chloramphenicol
What is the normal QTc interval?
< 440 ms
The QTc interval is considered to be borderline if it is >440 ms but <500 ms.
A prolonged QTc interval >500 ms is clinically significant
What is the MOA of most TCAs?
What type of side effects do they tend to cause?
What type of drugs should not be used alongside TCAs?
SNRI effects
Examples include - Amitriptyline, Imipramine
Antimuscarinic side effects
Avoid using with monoamine oxidase inhibitors (MAOIs), such as selegiline, and should be started at least 2 weeks after stopping the MAOI. There is a risk of developing serotonin toxicity.
What are the similarities and differences between first and second generation antipsychotics?
Give some examples?
First-generation (conventional or typical) antipsychotics, are strong dopamine D2 antagonists. However, each drug in this class has various effects on other receptors, such as serotonin type 2 (5-HT2), alpha1, histaminic, and muscarinic receptors.
First-generation antipsychotics have a high rate of extrapyramidal side effects, including rigidity, bradykinesia, dystonias, tremor, and akathisia. Tardive dyskinesia, which is involuntary movements in the face and extremities, is another adverse effect that can occur with first-generation antipsychotics. Neuroleptic malignant syndrome (NMS) can also occur with these agents.
Second-generation (novel or atypical) antipsychotics, with the exception of aripiprazole, are dopamine D2 antagonists, but are associated with lower rates of extrapyramidal adverse effects and TD than the first-generation antipsychotics. However, they have higher rates of metabolic adverse effects and weight gain.
1st generation: Chlopromazine Haloperidol Fluphenazine Trifluoperazine
2nd generation: Clozapine Olanzapine Quetiapine Risperidone Aripiprazole
Which class of Abx is administered during pregnancy can cause the child to have permanently yellow stained teeth and increased risk of dental cavities?
Tetracyclines
Children are susceptible to tetracycline related tooth staining until around age 8.
What is the recommended dose of Dexamethasone for Croup as per APLS guidelines?
150 mcg/kg
Max single dose 12 mg
What dose of IV/IO Adrenaline is used in paediatric cardiac arrest?
10 mcg/kg
What is the intubating dose of Atracurium?
The ‘intubating’ dose of atracurium is 0.3-0.6 mg/kg and subsequent doses are one-third of this amount. Satisfactory intubating conditions are produced within 90 seconds of administration.
How long after starting an IV Aminophylline infusion should a level be taken?
4-6 hours
List 6 drugs that can cause Stevens-Johnson syndrome and toxic epidermal necrolysis?
Tetracyclines Penicillins Vancomycin Sulphonamides NSAIDs Barbiturates
In Stevens-Johnson syndrome epidermal detachment is seen in less than 10% of the body surface area, whereas in toxic epidermal necrolysis epidermal detachment is seen in greater than 30% of the body surface area.
What dose of Flumazenil should be given IV in benzodiazepine overdose?
When should Flumazenil be avoided?
200 ug every 1-2 mins
Max dose 3 mg/hour
Flumazenil should be avoided if the patient dependant on benzodiazepine or takes tricyclic antidepressants as it can precipitate a withdrawal syndrome in these patients. In these circumstances it can cause seizures or cardiac arrest.
Give 3 indications for checking the INR in a child with possible Warfarin overdose?
Delayed presentation (>6 hours)
Patients with symptoms or signs of anticoagulation
Possible massive ingestion
Clotting studies including an INR are often organised routinely but small children who have ingested warfarin do not require INRs or follow up if they have been treated with 10 mg vitamin K. This dose of vitamin will completely reverse the anticoagulative effects of warfarin.
What effect can SSRIs such as fluoxetine and sertraline have on the newborn if started during the 3rd trimester?
Persistent pulmonary hypertension
How does Lidocaine act as an antiarrhythmic?
Blocks sodium channels in the heart.
This raises the depolarization threshold and makes the heart less likely to initiate or conduct early action potentials that may cause an arrhythmia.
What is the mechanism of action of Adenosine?
Opens K+ channels in heart, slowing conduction in the AV node
What may happen if Warfarin is given during the first trimester of pregnancy?
Fetal warfarin syndrome - nasal hypoplasia, bone stippling, bilateral optic atrophy, intellectual disability.
What biochemical abnormalities do you expect to see in theophylline overdose?
Hypokalaemia Hypomagnasaemia Hypophosphataemia Hyper or hypocalcaemia Hyperglycaemia
What is deficient in hereditary angioedema?
What can be given as prophylaxis?
What is the usual inheritance pattern?
How is it treated acutely?
C1 esterase inhibitor
Tranexamic acid can be given prophylaxis
Usually autosomal dominant
Angioedema and anaphylaxis due to C1 esterase inhibitor deficiency is resistant to adrenaline, steroids and antihistamines and needs treatment with C1 esterase inhibitor concentrate or fresh frozen plasma, which contains C1 esterase inhibitor.
Short-term prophylaxis for situations that may precipitate an attack can be achieved with C1 esterase inhibitor or fresh frozen plasma infusions prior to the event.
Long-term prophylaxis can be achieved with androgenic steroids such as stanozolol or antifibrinolytic drugs such as tranexamic acid.
What class of antibiotics should be avoided with Furosemide?
Macrolide Abx due to increased risk of hypokalaemia and therefore torsades de pointes
What are the side effects of Entonox?
N&V
Dizziness
Euphoria
Inhibition of Vitamin B12 synthesis
What dose of nebulised Budesonide is used for children aged 1 month to 18 years for croup?
2mg
May be repeated 12 hourly
How do NSAIDs cause renal adverse drug reactions?
Prostaglandins normally cause dilation of afferent arteriole
NSAIDs reduce prostaglandin levels
Therefore reduced renal plasma flow and GFR, but no effect on filtration fraction
What is the therapeutic range for Lithium?
0.4-0.8 mmol/l
Levels should be checked one week after starting therapy and one week after every change in dosage.
What is the MOA of Abciximab?
Abciximab (ReoPro) is a chimeric monoclonal antibody that is a glycoprotein IIb/IIIa receptor antagonist.
It inhibits platelet aggregation and is mainly used during and after coronary artery procedures such as angioplasty.
What antibiotics are used for post-exposure chemoprophylaxis for whooping cough if indicated?
Macrolide Abx
What effect does St John’s wort have on plasma theophylline concentration?
St John’s wort decreases plasma concentration of theophylline
Give 2 examples of Abx classes that increase plasma concentration of theophylline?
Macrolides - eg. Erythromycin
Quinolones e.g. Ciprofloxacin
What dose of IV adenosine is used in SVT?
6mg, then 12mg, then 12mg, at 1-2 minute intervals
Patients with a heart transplant, however, are very sensitive to the effects of adenosine and should receive a reduced initial dose of 3mg, followed by 6 mg and then 12 mg.
Summarise the 3 areas of effect of CCB overdose such as Verapamil?
Cardiac effects:
Negative inotropic
Negative Chronotropic
Negative dromotropic
Vasc smooth muscle tone effects:
Reduced afterload
Systemic hypotension
Coronary vasodilation
Metabolic effects:
Hypoinsulinaemia: insulin release is dependent on calcium influx into islet beta cells through L-type calcium channels
Calcium channel blocker-induced insulin resistance
What is Entonox a mix of?
50/50 mix of O2 and Nitrous Oxide (N2O)
Give examples of the different generations of Cephalosporin?
1st - Cefalexin, cefradine and cefadroxil
2nd - Cefuroxime
3rd - Cefotaxime, ceftazidime and ceftriaxone
Which drugs are known to undergo enterohepatic circulation?
MAD EARTOP
M - Morphine, methadone and metronidazole
A - Amphetamine
D - Vitamin D
E - Erythromycin A - Ampicillin R - Rifampicin T - Tetracyclines O - OCP P - Phenolphthalein
List drugs causing a prolonged QT interval?
Antimicrobials Erythromycin Clarithromycin Ciproflaxacin Moxifloxacin Fluconazole Ketoconazole
Antiarrhythmics Procainamide Sotalol Quinidine Amiodarone Flecainide
Antipsychotics (all have some risk) Risperidone Haloperidol Chlorpromazine Quetiapine Clozapine
Antidepressants Citalopram Fluoxetine Amitriptyline Clomipramine Dosulepin Doxepin Imipramine Lofepramine
Antiemetics Domperidone Droperidol Ondansetron Granisetron
Others Methadone Hydroxychloroquine Chloroquine Quinine Some antiretrovirals Loratadine
