pharmacology lectures Flashcards
what do you prescribe for streptococcal pharyngitis?
penicillin V 500mg qds for 10 days
how do antibiotics work?
antibiotics are molecules that work by binding a target site on bacteria
these target sites are defined as points of biochemical reaction crucial to the survival of the bacterium
the crucial binding site will vary with antibiotic class.
how do penicillins work?
they act on the cell wall of the bacteria and inhibits cell wall synthesis.
what are beta lactams?
penicillins
cephalosorins (cefalexin, cefuroxime, cefotaxime, cerftriaxone)
carbapenems (meropenem, ertapenem)
monobactams (aztreonam)
what types of antibiotics prevent nucleic acid synthesis?
quinolones
rifampin
what antibiotics prevent protein synthesis?
aminoglycosides (gentamicin)
tetracyclines (doxycycline)
Lincosamides (clindamycin)
macrolides (erythromycin, clarithromycin, azithromycin)
what antibiotics inhibit the metabolic pathways?
they do this by inhibiting folate synthesis
sulphonamides - sulphamethoxazole
trimethoprim - co-trimoxazole
what are some gram positive resistant organisms
MRSA - methicillin resistant stahylococcus aureus
VRE - vancomycin resistant enterococci (caused by cephalosporin use)
what causes resistance to certain penicillins?
what has been done to get around this resistance?
the production of beta lactase enzymes which hydrolyse penicillins
we add something that inhibits the beta lactamase eg clavulanate or tazobactam
amoxicillin plus clavulanate = co-amoxiclav
pipericillin plus tazobactam = tazocin
what antibiotics can be used when there is resistance to all other antibiotics?
carbapenems
however there is now also resistance to this
if someone has suspected sepsis what should you prescribe within the hour?
antibiotics
piperacillin/tazobactam and clindamycin
what should you treat group a beta haemolytic streptococcus skin infection with?
benzyl penicillin and clindamycin
what things do you need to consider when deciding if antibiotics are safe for the patient?
intolerance allergy and anaphylaxis side effects age renal and liver function pregnancy and breast feeding drug interaction risk of C.diff
what are cephalosporins good for?
good for people with penicillin allergy
work against some of the penicillin-resistant bacteria
they can get into different parts of the body e.g. meningitis
why are beta-lactams good for gram-positive bacteria?
because gram-positive bacteria have a thick cell wall and beta-lactams inhibit cell wall synthesis
what is the first line agent for cellulitis ?
flucloxacillin
what is the first line for strep throat?
PO penicillin V
IV benzylpenicillin
what is first line for pneumonia?
PO amoxicillin
IV benzylpencillin
what are forms of glycopeptides?
when are they used?
vancomycin
teicoplanin
only used for gram positive bacteria
use in MRSA
can be used in penicillin allergy
have to be used with caution because can cause renal impairment
when would you use a macrolide?
clarithromycin and erythromycin
s. aureus
beta haemolytic strep
atypical pneumonia pathogens (e.g. legionella, mycoplasma)
can be used in penicillin allergy
and in severe pneumonia
they work just as well orally and intravenously
when is it good to use clindamycin?
gram positive
can be used in cellulitis if penicillin allergic
can be used for necrotising fasciitis (turns off nasty towns made by gram positive bugs)
when is it good to use tetracyclines ?
e.g. doxycycline
broad spectrum but mainly for gram positive
can use in cellulitis is penicillin allergy
can be used in chest infections
what type of infections are caused by gram negative bacteria?
UTIs
diarrhoea
intra-abdominal infections
gall bladder infections - billiard sepsis
what is the main draw back of ciprofloxacin?
it can cause C.diff
so tend to avoid in elderly patients
why is ciprofloxacin good and when is it used ?
it gets everywhere in the body - head, bowel, skin
not many bugs are resistant to it
used for gram negative
used in UTI, gall bladder infections, abdominal infections
what is trimethoprim used for?
it is broad spectrum but is mainly used for gram negatives
used in UTIs
when is nitrofurantoin used?
gram negative - UTIs
why are penicillins not good for gram negatives?
because gram negatives produce lots of the enzymes that hydrolyse penicillin
however some beta lactams can be used for gram negatives e.g. cephalosporins
respiratory drug nomenclature
…..mab = monoclonal antibody (reslizumab)
…..sone = corticosteroid (dexamethasone)
…..terol - bronchodilators (salmeterol)
…..lone = corticosteroid (prednisolone)
….nib = kinase inhibitor (nintedanib)
what are inhaled pharmacological and what are mechanisms of administration ?
what are the delivery systems for inhaled drugs?
inhaled medicines are delivered directly to the lung via the oral or nasal route
inhaler devices allow drugs to penetrate deep into the lung and to achieve the correct dose, inhalers deliver dry powder formulation
nebulisers deliver medication in theorem of aerosols
pressurised metered-dose inhalers
spacer devices
dry powder inhalers
nebulisers
what are some causes of bronchocontriction?
asthma
copd
constriction of the airways due to tightening of airway smooth muscle, luminal occlusion by mucus and plasma and airway wall thickening.
Leads to airflow obstruction
what two main categories are bronchodilators divided into?
adrenergic (sympathetic) - bronchodilator
anti-cholinergic (parasympathetic - block bronchoconstriction)
how do bronchodilators work?
they are beta2 adrenoreceptor agonists
they act on beta2 adrenoreceptors to cause smooth muscle relaxation and bronchodilation, they also inhibit histamine resale from lung mast cells.
what are some examples of bronchodilators ?
SABA
LABA
what is the muscarinic receptor activation for bronchoconstriction?
acetylcholine causes muscle contraction by acting on the muscaranic receptors on the smooth muscle cells which causes muscle contraction in the airways.
Act is released by parasympathetic nerves
how do anti-cholinergic prevent bronhoconstriction?
acetylycholine antagonists (anticholinergics) block acetylcholine binding to muscarinic receptors and prevents bronchoconstriction.
anticholinergic compounds block muscarinic receptors on airway smooth muscle, glands and nerve to prevent muscle contraction, gland secretions and enhance neurotransmitter release.
what are some examples of muscarinic receptor antagonists?
ipratropium bromide
tiotropium bromide
atropine - old one that was used but has many side effects.
what drugs can be used for anti-inflammatory in lung disease?
glucocorticoids aka corticosteroids suppress inflammation via several mechanisms. they are the most effective anti-inflammatory for asthma (they improve QOL in patients with asthma, improve lung function, reduce frequency of exacerbations and can help to prevent irreversible airway changes
how ever they are relatively ineffective in COPD, CF and IPF
what are the side effects of ICS?
high doses of ICS are often used in COPD
they overuse can lead to long term side effects such as:
loss of bone density
adrenal suppression
cataracts, glaucoma
titrate to the lowest effective dose to reduce the chances of side effects
how is bronchiectasis managed?
it is challenging
antibiotics treat the infective elements of bronchiectasis
physical therapies clear the air ways
surgery and transplantation may be needed for severe disease
strategies to reduce the symptoms
- mucolytics
- beta 2 agonists most useful in COPD/asthma/bronchiectasis overlap syndromes
- anticholinergics have limited effect
- ICS have limited effects
how is pulmonary fibrosis managed?
treatment is limited
some forms of fibrosis respond to corticosteroids
pirfenidone and nintedanib are new drugs that significantly slow the rate of disease progression in IPF
usually how long should a patient not eat before surgery?
6 hours
what is done if a patient has eaten in the past 6 hours but needs emergency surgery?
or if they have a blockage meaning they have a full abdomen?
they have a rapid sequence induction
quick hit short period of time which doesn’t give time for aspiration reflux and aspiration of gastric contents
if someone is unstable, but needs emergency surgery what she be done before inducing anaesthesia?
pre-optimisation
- invasive blood pressure monitoring
- urinary catheter
- central venous access
- inotropic support
- cardiac output monitoring
- the broad aim of pre-optimisation is to mammies oxygen delivery peri-operatively to supra-normal levels.
what drugs should be omitted per-operatively in the elective surgeries?
> ACE inhibitors (“…prils”) - stop 24 to 72 hours before
angiotensinogen receptor antagonists (‘sartans”) - stop 24-72 hours before
anti-tumour necrosis factor - stop 2 weeks before
platelet inhibitors - aspirin, clopidogrel, prasugrel - stop 7-10 days before
DOACS - stop 4 days before
rivaroxaban, apixaban, eidxoban - stop 3 days before
why are NSAIDS avoided with surgery?
they increase the risk of intraoperative bleeding
do not use within 24-48 hours of operation because the increase the risk of post operative bleeding
do not use in asthmatic
can cause renal failure if given during blood loss or during episodes of hypotension
avoid NSAIDS in those with renal impairment, hyperkalaemia, hypovolaemia, circulatory failure, severe liver dysfunction, cardiac disease, MI, CVA
THEY SHOULD BE USED QITH GREAT CAUTION PERIOPERATIVELY
what things are often given intraoperatively ?
oxygen fluids blood/blood products antibiotics anaesthesia analgesia muscle relaxation
what are the common inhalation anaesthetic agent to keep the patient asleep?
desflurane - possible reduction in post operative cognitive dysfunction, rapid recovery particularly in the obese. however big contributor to global warming
sevoflurane
what are the intravenous agents used to induce anaesthesia?
propofol - this is the one that should be used - can also be used for the maintenance of anaesthesia (know as total intravenous anaesthesia)
ketamine - not often used
what are the two types of muscle relaxation?
depolarising - suxmethonium - short rapid onset and short duration and rapid offset- used in rapid sequence induction
non-depolarising - rocuronium - takes longer to wash in and build up concentrations because it is a competitive block. Takes 3 or 4 minutes to work. wears off gradually, slow offset. Duration of onset can last from 20-40 minutes
they lead to muscle relaxation and paralysis
they all work by mimicking acetylcholine
what can be used to reverse neuromuscular block caused by rocuronium?
sugammadex
what things can be given postoperatively?
analgesia
fluids/blood products
inotropes/vasopressors
antiemetics/anti-coagulants/antibiotics
what is the total blood volume for adults>
70 mls/kg
what are the different types of fluid?
crystalloids
colloids - rarely used
what happens if you resuscitate someone with normal saline for a long period?
they become hypernatraemic
they will also get hyperchloraemia
they end up acidotic
hyperchloraemia acidosis
how is glucose transported into cells?
it is co transported into cells with potassium so if you give someone loads of sugar it will drop their potassium
what are the different types of fluid loss?
sensible - fluid loss you can measure and see
insensible - hard to measure
what do you need to consider when prescribing paracetamol?
liver impairment severe cachexia (less than 50kg)
what do you need to consider when prescribing NSAIDS?
renal impairment - so check renal function and platelet count
risk of GI bleeding
history of and ulcer
if they have asthma
concurrent medications: things that also increases risk of things mentioned above - warfarin, digoxin and steroids
what are common weak opioids?
Codeine
Tramadol
dihyrocodeine
after trying a weak opioid and it having minimal effect what might you try?
strong opioid
- morphine
- fentanyl
- diamorphine - given primarily via injection or infusion
- oxycodone
- buprenorphine
what do you need to consider before starting a strong opioid?
ask the patient have they even taken before, how did they find it if they have?
age and frailty - small doses may be needed
any co-morbitities
any reduced renal function (morphine in people with low renal function can cause more side effects so in people with eGFR<30 always use oxycodone)
will they take them as prescribed?
are they driving?
patient concerns?
how potent is codeine and tramadol compared to oral morphine?
codeine and tramadol are 1/10th as potent as oral morphine.
what type of morphine and oxycodone would you prescribe for background pain?
modified release - 12 hours
morphine (MST - tablet, Zomorph - capsule )
Oxycodone - oxycontin
what type of morphine and oxycodone would you prescribe for breakthrough pain?
immediate release
duration of action = 4 hours
morphine - oramorph (liquid), sevredol (tablet)
oxycodone - oxynorm - liquid or capsule
what should you do when prescribing opioids?
always slow low
titrate dose according to pain and PRN usage
you should always prescribe PRN antiemetics and a stimulant laxative in case of the side effects
what should the PRN dose of opioids be?
PRN doses as a general rule are 1/6th of the 24hour dose
what are the side effects of morphine?
common - constipation, nausea, sedation, dry mouth
Less frequent - psychomimetic effects, confusion, myoclonus
rare - allergy, respiratory depression, pruritus
what opioids come in the form of patches?
Fentanyl and buprenorphine
when might opioid patches be needed?
what are the problems with the patches?
if there are intolerable side effects
if there are oral route difficulties - compliance or dysphagia
renal impairment
problems:
takes 1-3 days to reach analgesic concentrations when first increased so no not use in acute pain
needs to be applied to hairless, dry, non inflamed skin
avoid heat pads as they will increases the rate of absorption
what are more renal friendly opioids?
fentanyl
buprenorphine
methadone
alfentanil
what are the different types of pain?
nociceptive pain - pain that arises from actual or threatened damage to non-neural tissue and is due to activation of nociceptors
Neuropathic pain - pain caused by a lesion or disease of the somatosensory nervous system
nodplastic pain - pain that arises from altered nociception despite no clear evidence of actual or threatened tissue damage causing the activation of peripheral nociceptors or evidence from disease or lesion of the somatosensory system causing pain.
what is allodynia?
when there is pain due to a stimulus that does not normally provoke pain
what is dysesthesia?
an unpleasant abnormal sensation, whether spontaneous or evoked
what is acute pain and chronic pain?
acute - less than 12 weeks
chronic - continuous pain lasting more than 12 weeks - can be cancer and non cancer chronic pain
