Pharmacology 6: Immunosuppression and RA, and pharmacology of airway control Flashcards

1
Q

overall mechanism of action of corticosteroids?

A

inhibitors of gene expression: lipophilic so capable of crossing PM to bind to cytoplasmic receptor.
Forms a hormone-receptor complex which enters nucleus and binds to intra-nuclear receptor and interacts with specific regions of DNA to alter rate of transcription of specific genes.
inhibit all stages of T cell activation
prevent IL-1 and -6 production by macrophages
especially decrease TNF-alpha prod

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2
Q

corticosteroid ADRs?

A

hypertension
oral candidiasis- increased infection risk as immunocompromised
osteoporosis- as increased osteoclast activity, so may give Vit D supplements
weight gain- moon shaped face and central obesity- Cushing’s syndrome
bruising, purple striae
hyperglycaemia, diabetes
growth suppression in children
gastric ulcers- as transrepression of COX-2 required for PG synthesis in stomach for alkali and mucus prod= protective

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3
Q

mechanism of action of azathioprine (an immunosuppressant)?

A

cytotoxic antimetabolite that acts selectively on cells with a higher mitotic rate.
primary action= inhibition of purine metabolism, which reduces both DNA and RNA synthesis.
Pro-drug- activated to 6-Mercaptopurine (6-MP)

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4
Q

active form of azathioprine?

A

6-Mercaptopurine (6-MP)

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5
Q

which enzyme is required for elimination of 6-Mercaptopurine (6-MP)?

A

TPMT: thiopurine methyltransferase- subject to high rate of genetic polymorphism.

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6
Q

how does expression of enzyme TPMT- thiopurine methyltransferase, affect tment with azathioprine and why?

A

drug elimination requires this enzyme.
So high levels of enzyme expression will allow rapid elimination, hence undertreatment.
low levels of expression will lead to increased toxicity.

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7
Q

ADRs of azathioprine?

A

BM suppression, must monitor FBC
increased infection risk
emergence of malignant cell lines, espec increased risk in transplanted patients**
hypersensitivity reactions e.g. dizziness, vomiting, diarrhoea, rash
hepatitis- monitor LFTs

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8
Q

how does cyclophosphamide act as an immunosuppressant?

A

prodrug activated by CYP450s to produce active alkylating electrophilic cytotoxic metabolites whihc cross link DNA, inhibiting its replication
selectively acts on cells with higher mitotic rate.
suppress both T and B cells

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9
Q

ADRs of cyclophosphamide?

A
excreted by kidney- can induce bladder cancer due to concentration of acrolein metabolite in urine, acrolein= toxic to bladder epithelium, can cause haemorrhagic cystitis, can be prevented through use of aggressive hydration and/or Mesna, most adjust dose accordingly if renal impairment
lymphoma
leukaemia
infertility
teratogenesis
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10
Q

agent of choice in transplant immunosuppression?

A

mycophenolate mofetil (MM)

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11
Q

ADRs of mycophenolate mofetil?

A

leuko and neutropenia
myelosuppression
increased infection risk- espec. viral

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12
Q

how does methotrexate work in malignant disease?

A

acts an an antifolate, with folate being necessary for synthesis of purines and thymidine= precursors to building blocks in DNA synthesis.
Binds to DHFR (dihydrofolatereductase) as competitive reversible inhibitor- which uses folate as a substrate.
folate= role in single carbon transfer reactions central to synthesis of purines and thymidine.
Action selective during S phase of cell cycle in cells with high mitotic activity, so greater toxic effect on rapidly dividing cells e.g. GI and oral mucosa- replicate DNA more frequently.

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13
Q

ADRs of methotrexate?

A

GI effects as gut mucosa= high mitotic activity- diarrhoea, anorexia, dyspepsia, abdom discomfort, GI ulceration e.g. mouth
may also cause hair loss as hair follicle cells= rapidly dividing
hepatotoxicity, hepatitis- may appear jaundiced, cirrhosis
pulmonary fibrosis and interstitial pneumonitis- dyspnoea, cough, crackles- would show ground glass opacification on CT
BM suppression- may be fatigued, susceptible to infections

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14
Q

monitoring required with methotrexate?

A

FBC- as BM suppression risk
LFTs- as risk of hepatotoxicity
Us and Es-as mainly eliminated via kidneys
monitor resp symptoms at each visit e..g. dyspnoea and cough, stop tment if pneumonitis supected
dose monitoring if combined with aspirin or other NSAIDs- NSAIDs displace drug from plasma proteins- MTX has 50% protein binding

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15
Q

name 2 diseases sulfasalazine is used in the tment of?

A

RA

IBD

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16
Q

ADRs of sulfasalazine?

A
nausea
abdom pain
diarrhoea
vomiting, nausea
fatigue
headache
myelosuppression
hepatitis
allergic rash- anaphylaxis
so must do LFTs and FBC regularly
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17
Q

ADRs of B2 agonists used as relievers in asthma?

A
skeletal muscle tremor
tachycardia
dysrhythmia
palpitations
headache
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18
Q

features of temporal (giant cell) arteritis?

A

malaise
jaw claudication
severe peri-orbital headache

giant cell arteritis can affect other arteries of head and neck,large vessel vasculitis, no infection

=inflammation of temporal arteries= terminal branches of ECA, chronic inflammatory process,severe pain if patient tries to brush their hair, medical emergency as inflammation can spread to involve ICA- opthalmic artery- central artery of retina- sudden blindness

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19
Q

why is azathioprine associated with increased risk of skin cancer?

A

causes accumulation of 6-thioguanine in patient’s DNA, which might trigger cancer on exposure of patient to UV light

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20
Q

people giant cell arteritis is most common in?

A

women

aged >35

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21
Q

what is given to all patients prescribed steroids for >3wks in case patient requires tment in an emergency?

A

blue steroid card- patients may enter an addisonian crisis if suddenly stop their steroid medication as steroids will have been suppressing release of ACTH from anterior pituitary that normally stimulates steroid release from adrenals, so HPA axis suppression, so on stopping steroids, endogenous prod of steroids may be so low with adrenal insufficiency that an addisonian crisis results= patient may be very confused, hypotensive, nausea, vomiting, severe abdominal pain, seizures

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22
Q

most common cause of an addisonian crisis?

A

abrupt withdrawl of steroid medication

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23
Q

how is giant cell arteritis treated?

A

initial dose of prednisolone= 40–60 mg daily (the higher dose being used if visual symptoms occur). Treatment should be continued until remission of disease activity and doses are then reduced gradually to about 7.5 –10 mg daily for maintenance. Relapse is common if therapy is stopped prematurely. Many patients require treatment for at least 2 years and in some patients it may be necessary to continue long-term low-dose corticosteroid treatment.

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24
Q

indications for methotrexate?

A

RA- used in combination with other DMARDs to provide best outcome, and with biologics e.g. etanercept and infliximab.
malignancy
Crohn’s
Psoriasis
unlicensed roles= maintenance therapy in vasculitis

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25
how is methotrexate thought to work in tment of inflammatory diseases e.g. RA?
increases adenosine, through inhibition of enzymes involved in purine metabolism, which is a potent, endogenous anti-inflammatory mediator that inhibits neutrophil adhesion, phagocytosis, and superoxide generation. MTX also causes apoptosis of activated CD4 and CD8 T cells, but not of resting T cells.
26
when might adenosine be given IV to treat a patient?
for arrhythmias e.g. re-entry, as short t1/2 <10s, acts on alpha 1 adrenoceptors at AV node, and enhances K+ conductance, hyperpolarising cells so conduction at AV node slowed/prevented.
27
how often is methotrexate given and why?
once weekly as metabolites (polyglutamates) are long lived- long t1/2s 2.5 mg tablets, may take up to 8 for tment of moderate to severe active RA= max wkly dose 20mg
28
if a patient is take methotrexate once weekly, what else must they also take once weekly?
folic acid= as MTX antagonises folate action in body, so taken NOT on same day as MTX as folate would then be ineffective folate required for DNA synthesis and repair, and for rbc synthesis to prevent anaemia.
29
what is it important to note if thinking of commencing a young woman on methotrexate?
it is teratogenic as inhibits folate action, so can cause neural tube defects hence pregnancy should be avoided until at least 3mnths post stopping of MTX tment
30
indications for sulphasalazine?
RA | inflammatory bowel disease
31
immunological effects of sulphasalazine?
T cells- inhibit proliferation possible result in apoptosis inhibition of IL-2 production neutrophils- reduced chemotaxis and degranulation
32
drug class for sulphasalazine?
aminosalicyclate combination of 5-aminosalicylic acid (‘5-ASA’) and sulfapyridine; sulfapyridine acts only as a carrier to the colonic site of action in treating IBD but still causes side-effects. sulfapyridine important in RA as absorbed into blood so can have sytemic effects.
33
other drugs apart from sulphasalazine that are aminosalicylates?
balsalazide olsalazine sulphasalazine has sulphonomide component= sulfapyridine- absent from other drugs
34
indications for azathioprine?
IBD SLE vasculitis- maintenance therapy here and in SLE RA
35
what must be monitored if patient on azathioprine?
FBC
36
factors limiting use of biologics in RA?
expense | profile of ADRs e.g. ...
37
important drug-drug interactions of aspirin, in terms of treating a patient with RA?
``` corticosteroids= PDs, both drugs increase risk of gastric ulcer formation as inhibit PG production in stomach necessary for mucus and alkali production, aspirin= inhibits COX, and corticosteroids= transrepression of COX-2. methotrexate= PKs, aspirin reduces excretion of MTX NSAIDs= increase SEs as both inhibit COX in stomach. ```
38
X-ray changes with RA?
bony erosions joint subluxation following tendon rupture due to inflammation osteopenia
39
overall summary of RA pathophysiology?
AI- auto-antibodies targeted against synovium systemic- extra-articular manifestations e.g. CVD inbalance between pro- and anti-inflammtory cytokines, pro- dominate Cellular and humoral immune response, cellular= type IV hypersensitivity, cytokine prod by T helper cells, TNF-alpha fundamental in producing joint damage. Humoral= autoantibodies e.g. RF, form immune complexes- activate complement- inflammatory cell recruitment. Pannus= abnormal fibrovascular tissue resulting from misshapen growth of inflamed synovium, promotes bone destruction, prevents cartilage nutrition and produces subluxation.
40
overall summary of SLE pathophysiology?
type III hypersensitivity reaction, AI chronic disease non-organ specific, circulating immune complexes, anti-dsDNA and anti-nuclear antibodies joint arthritis, butterfly/malar rash- skin, kidneys- hypertension, renal failure, CNS and PNS- seizures, fever
41
Raynaud's phenomenon may occur secondary to both RA and SLE, what is it?
blood supply affected to certain parts of body, commonly fingers and toes. blood vessels go into a temporary spasm which blocks the flow of blood. This causes the affected area to change colour to white, then blue and then red as the blood flow returns.
42
function of DMARDs and examples?
``` e.g. in RA- suppress disease process and hence halt progression, limiting damage, and can actually lead to clinical improvement in underlying condition. azathioprine sulphasalazine methotrexate biologics e.g. etanercept and infliximab ```
43
what must be tested in patients before prescribing azathioprine?
thiopurinemethyltransferase activity as gene highly polymorphic
44
what are calcineurin inhibitors and when are they used?
e.g. ciclosporin and tacrolimus bind to particular proteins (ciclosporin to cyclophillin and Tacrolimus binds to tacrolimus-binding protein ) and these complexes then bind to calcineurin which is an important factor in T cell activity as normally exerts phosphatase activity on the nuclear factor of activated T cells and this factor then migrates to the nucleus to start IL-2 transcription, so active against helper T cells, preventing production of IL-2 via calcineurin inhibition. widely used in transplantation, and in psoriasis and atopic dermatitis • Calcineurin normally exerts phosphatase activity on the nuclear factor of activated T cells. This factor then migrates to the nucleus to start IL-2 transcription
45
what must be checked regularly if patient on a calcineurin inhibitor e.g. transplant patient, and why?
eGFR and BP as causes renal toxicity
46
why are multiple DDIs possible with calcneurin inhibitors e.g. ciclosporin, used in atopic dermatitis, psoriasis and transplant patients?
met via CYP450 system of enzymes in liver
47
give 2 indications for myocphenolate mofetil?
transplant patients | induction and maintenance in lupus nephritis
48
active metabolite of mycophenolate mofetil which can be monitored in transplant patients given the drug?
mycophenolic acid
49
mechanism of action of mycophenolate mofetil?
Is a prodrug derived from fungus Penicillium stoloniferum Inhibits inosine monophosphate dehydrogenase (required for guanosine synthesis) impairs B- and T-cell proliferation spares other rapidly dividing cells (due to guanosine salvage pathways in other cells)
50
indication of neutropenia on examination of a patient being treated with mycophenolate mofetil?
mouth ulcers
51
indications for cyclophosphamide?
lymphoma leukaemia lupus nephritis wegener's granulomatosis (ANCA vasculitis)
52
main active metabolite of cyclophosphamide?
4-hydroxycyclophosphamide
53
action of dihydrofolate reductase?
catalyses the conversion of dihydrofolate | to the active tetrahydrofolate- the key carrier of one-carbon units in purine and thymidine synthesis
54
how may methotrexate administration be altered if currently given orally but partial response or nausea occurring?
give subcutaneously
55
where is sulfasalazine cleaved into its constituent parts?
large bowel 5-ASA= largely unabsorbed or EH circulation sulfapyridine= absorbed, and highly protein-bound
56
factors favouring sulfasalzaine use in practice?
``` safe in pregnancy (contrast to MTX) long term blood monitoring not always needed effective few DDIs no carcinogenic potential* ```
57
TNFalpha inhibitors that can be used in RA?
etanercept- fusion protein adalimumab golimumab infliximab= all monoclonal antibodies- made specifically to block any given substance in the body, or to target any specific cell type
58
biologic that can be used in treating lymphoma?
rituximab= monoclonal Ab= depletes B cells
59
biologics for RA that don't act to inhibit TNF-alpha?
rituximab tocilizumab- monoclonal Abs abatacept- fusion protein- usually based on naturally occurring receptor
60
what must be screened for before commencing anti-TNF tment and why?
TB tment may cause reactivation of latent TB as TNF-alpha produced by macrophages in response to M.TB infection, and is essential for development and maintenance of granuloma
61
effects of blocking TNF-alpha
reduce inflammation, cytokine cascade, leukocyte recrutiment to joint reduce angiogenesis- VEGF levels reduce joint destruction- MMPs, bone resoprtion and erosion, and cartilage bdown
62
how does rituximab work?
binds to CD20 found on a subset of B cells- B cells presnt antigen to T cells, and produce cytokines and antibodies causes B cell apoptosis
63
example of class of drugs that may be used in RA in the future?
JAK inhibitors- janus kinase inhibitors, JAK= intracellular enzymes important in cell signalling
64
ADRs of cytokine modulators- biologics?
associated with infections, sometimes severe, including tuberculosis, septicaemia, and hepatitis B reactivation. Other side-effects include nausea, abdominal pain, worsening heart failure, hypersensitivity reactions, fever, headache, depression, antibody formation (including lupus erythematosus-like syndrome), pruritus, injection-site reactions, and blood disorders (including anaemia, leucopenia, thrombocytopenia, pancytopenia, and aplastic anaemia).
65
what remodelling of the airways takes place in LT and poorly controlled asthma?
basement membrane thickening smooth muscle hypertrophy and hyperplasia mucous gland hypertrophy
66
5 defining characteristics of asthma?
``` chronic inflammatory process airway hyperesponsiveness variable and widespread airflow obstruction susceptibility reversibility ```
67
5 factors that contribute to airway narrowing in asthma?
bronchial wall thickening with inflammatory cell infiltration smooth muscle contraction epithelial shedding mediated by eosinophils mucus over prod, abnormal mucus- forms plugs mucosal oedema
68
5 steps in treating asthma?
``` 1= mild intermittent= inhaled short-acting beta 2 agonist e.g. salbutamol 2= regular preventor therapy= add inhaled steroid, dose appropriate for disease severity 3= initial add-on therapy= add inhaled long-acting beta 2 agonist e.g. salmeterol. Can increase inhaled steroid dose if benefit from long acting beta 2 agonist but control still inadequate. If long-acting no response, stop and increase inhaled steroid. If control still not good enough with last 2 options, trial other therapies e.g. leukotriene receptor antagonist OR methylxanthine e.g. theophylline. 4= persistent poor control= increase inhaled steroid, add 4th drug e.g. LKTRA, methyxanthine or beta 2 agonist tablet 5= use daily steroid tablet (oral), maintain high dose inhaled ```
69
describe the early phase response in asthma
type I hypersensitivity reaction, immediate response which reaches maximum in 20 mins interaction of allergen and specific IgE antibodies produced by plasma cells, causing mast cell degranulation and release of histamine, PGD2 and leukotrienes, which causes bronchoconstricition.
70
describe the late phase response in asthma
type IV (delayed) hypersensitivity, 3-12 hrs after exposure to antigen inflammation, mast cells and T helper 2 cells release cytokines e.g. IL-4 and 5, that attract eosinophils and neutrophils. eosinophils release leukotriene C4 and other mediators, some toxic to epithelial cells so cause shedding. eosinophils very sensitive to steroid therapy*
71
why must short acting beta 2 agonists not be used regularly?
reduce asthma control | with regular use, mast cell degranulation in response to allergen increases
72
why are short-acting beta 2 agonists used in asthma?
for mild/intermittent asthma reverse bronchoconstriction and prevent it on exercise use on an as-required basis
73
examples of short-acting beta 2 agonists used in asthma
salbutamol | terbutaline
74
what is formoterol?
beta 2 agonist used in asthma tment, can have fast onset and long duration if inhaled, or slow onset and short duration if given orally.
75
when are inhaled corticosteroids required in asthma?
symptoms 3 or more times a week waking at least once a wk using a beta 2 agonist 3 or more times a wk exacerbation requiring oral steroids in the last 2 yrs
76
describe the 2 mechanisms by which steroids act in the nucleus
transrepression and transactivation activate transcription of anti-inflammatory genes e.g. beta 2 adrenergic receptors- so can increase efficacy of beta 2 agonist when giving an inhaled corticosteroid, and annexin-1. inhibit pro-inflammatory pathways, prevent translation of pro-inflammatory proteins e.g. inhibit COX-2- so risk of gastric ulceration*
77
a lipophilic side chain on D-ring of corticosteroids has what benefits?
very high affinity for glucocorticoid receptor increased uptake and dwell time in tissue on local application rapid inactivation by hepatic biotransformation following systemic absorption
78
why does beclomethasone have good systemic absorption?
not subject to much 1st pass metabolism, absorbed through gut and lungs *contrast to budesonide and fluticasone which are subject to extensive 1st pass met.
79
what must be done before initiating a new drug therapy at step 3 in treating asthma?
re-check med compliance check inhaler technique- right inhaler and being used correctly eliminate trigger factors
80
why is a long acting beta 2 agonist e.g. salmeterol or formoterol, used instead of increasing the dose of inhaled corticosteroid at step 3 in asthma tment?
been shown in trials that this is more efficacious, probably as most of the action of corticosteroids is achieved at low doses- relatively flat dose-response curve.
81
examples of combination inhlaers that can be used in asthmatic pateints requring step therapy?
``` symbicort= budesonide/formoterol seretide= fluticasone/salmeterol fostair= beclometasone/ formoterol ```
82
why are combination inhalers used in step 3 of asthma tment?
makes taking tment easier improves adherence- can't use agonist without using steroid safety- as want them both together, using agonist without inhaled corticosteroid is potentially harmful potentially cheaper than 2 individual inhalers 1 versus 2 prescriptions to worry about
83
when might leukotriene receptor antagonsits be used in treating asthma and why?
step 3/step 4 add-on therapy inhibit actions of leukotriene C4 released by mast cells and eosinophils which can induce bronchoconstriction, mucosal oedema and mucus secretion, and promote inflammatory cell recrutiment, and cause epithelial shedding.
84
ADRs of leukotriene receptor antagonists?
``` fever dry mouth angioedema anaphylaxis arthralgia gastric disturbances ```
85
action of methylxanthines?
antagonise adenosine receptors | previously thought to inhibit phosphodiesterase and increase cAMP
86
what limits use of methylxanthines e.g. theophylline and aminophylline for asthma in practice?
often poorly efficacious narrow therapeutic window frequent SEs: nausea, headache, reflux AND potentially life-threatening toxic complications= tachycardia and arrhythmias and fits/ psychomotor agitation met. by CYP450 so important DDIs e.g. increased risk of toxicity with erythromycin and ciprofloxacin antibiotics as enzyme inhibitor so reduced xanthine metabolism.
87
what else can be added other than a methylxanthine or leukotriene receptor antagonist as a step 3/step 4 add-on therapy?
anticholinergic e.g. tiotroprium bromide= long-acting, once daily licensed for COPD and severe asthma, reduces exacerbations
88
ADRs of tiotropium bromide (anti-muscarinic) ?
dry mouth urinary retention glaucoma dizziness
89
after oral steroids in step 5 of asthma tment, what else can be used?
anti-IgE= prevent IgE binding to mast cells and causeing their degranulation, but very expensive. May reduce exacerbation rates in those not controlled on oral steroids.
90
what is recommended in terms of tment when asthma is well controlled?
stepping down if not, may be receiving higher dose than necessary, and pts should be maintained at lowest possible dose of inhaled corticosteroid.
91
most effective size of particles in inhaler devices?
1-5 microns- settle in small airways if too big, can't reach small airways too small- not deposited in lungs, and taken into alveoli then breathed out
92
features of patient with acute, severe asthma?
can't complete sentences pulse> or equal to 110 beats/min RR > or equal to 25/min PEFR between 33 and 50% of that predicted/best
93
why is ipratropium not used straight away in acute severe asthma?
bronchodilation induced more slowly, and less intense
94
features of life-threatening asthma?
same as acute severe, plus cyanosis PEFR <33% that predicted feeble resp effort
95
tment of acute severe asthma?
Oxygen, high flow – aim to keep O2 94-98% sat Nebulised salbutamol – continuous if necessary, oxygen driven Oral prednisolone ~40 mg daily for 10-14 days - can be stopped without tailing down If moderate exacerbation not responding, or acute severe/life threatening, add nebulised ipratropium bromide Consider IV aminophylline if no improvement and life threatening features not responding to above treatment (BEWARE if taking oral theophylline ).
96
if a patient is receiving IV cyclophosphamide, what might they be given to reduce their risk of bladder cancer?
mesna
97
in what different ways does activation of beta 2 adrenoceptors cause bronchial smooth muscle relaxation?
beta 2= Gs GPCR= activation activates adenylate cyclase, which increases cAMP and PKA PKA reduces affinity of light chain myosin for Ca2+ PKA also reduces IC Ca2+ by increasing amount sequestered by SER and PKA phosphorylates K+ channels, causing increased K+ efflux so hyperpolarisation which reduces contractility and reduces actvity of voltage-activated Ca2+ currents, AND there may be additional hyperpolarisation due to Gs independent increase in Ca2+ activated K+ currents.