drugs Flashcards
thyroid hormones mechanism of action
synthetic thyroxine
indications thyroid hormones
hypothyroidism, diffuse non-toxic goitre, thyroid carcinoma
eg thyroid hormones
levothyroxine sodium (thyroxine)
SEs thyroxine
occur at excessive dosage and at start of therapy with rapid inc in metabolism
arrhythmias, palpitations, skeletal muscle cramps and weakness, vomiting, diarrhoea, tremors, restlessness, headache, flushing, sweating, fever, excessive weight loss and sometimes anginal pain
cautions/contraindications thyroxine
panhypopituitarism or predisposition to adrenal insufficiency from other causes (initiate corticosteroid therapy before starting levothyroxine), lower starting dose in the elderly or CV dis.
Antithyroid drugs mechanism of action
interfere with synthesis of thyroid hormones
indications antithyroid drugs
long term management of thyrotoxicosis and to prepare pts for thyroidectomy
may be given with propanolol initially for symptom control
egs of antithyroid drugs
carbimazole
propylthiouracil
high dose continued til pt euthyroid, usually after 4-8 weeks, and dose is then gradually reduced over 6-24 months to a maintenance dose.
why would a combo of carbimazole and thyroxine be given
in a blocking-replacement regimen (not in preg)
SEs antithyroid drugs
bone marrow suppression - pts should be asked to report symptoms of infec esp sore throat. WCC performed if any clinical evidence of infec, and rx stopped immediately if clin evidence of neutropenia.
Nausea, GI disturbance, headache, rashes and pruritus occurs w carbimazole
Cutaneous vasculitis, hepatic necrosis, nephritis and lupus like syndrome with propylthiouracil
cautions and contraindications antithyroid drugs
liver disorders; over treatment can result in rapid development of hypothyroidism
What does the adrenal cortex normally secrete?
Hydrocortisone (cortisol) which has glucocorticoid activity and weak mineralocorticoid activity. It also secretes the mineralocorticoid aldosterone.
In primary adrenal insufficiency how is physiological replacement best achieved?
With corticosteroids - hydrocortisone and the mineralocorticoid fludrocortisone
hydrocortisone alone does not usually provide sufficient mineralocorticoid activity for complete replacement
In hypopituitarism what is given?
Glucocorticoids - aldosterone is not necessary as production is regulated by the renin-angiotensin system
mechanism of action for corticosteroids
replacement and anti inflam reactions
mech of action for anti inflam actions corticosteroids
induction of the synthesis Ikß an inhibitory protein which binds NF-Kappa B
Indications corticosteroids
inflam conditions - joints, lungs, skin, bowel, acute transplant rejection, autoimmune conditions, nephritic/nephrotic syndrome, cerebral oedema, acute hypersensitivity reactions
replacement therapy in adrenal insufficiency and hypopituitarism
dexamethasone
potent steroid with insignificant mineralocorticoid activity - makes it useful for high dose therapy in conditions where fluid retention (mineralocorticoid SE) would be a disadvantage e.g. cerebral oedema
prednisolone
predominantly glucocorticoid activity and is the corticosteroid most commonly used by mouth for disease suppression
hydrocortisone and cortisone - why not suitable for disease suppression on a LT basis?
high mineralocorticoid activity resulting in fluid retention
hydrocortisone? e.gs of uses
used for adrenal replacement therapy and IV in the emergency management of some conditions, e.g. severe ulcerative colitis, anaphylactic shock
other uses corticosteroids
inhalation in asthma
rectal admin in inflam bowel dis
topically in the inflam treatment of skin disease
examples of corticosteroids
prednisolone
hydrocortisone
dexamethasone
methylprednisolone
SEs corticosteroids
glucocorticoid SE’s incl diabetes and osteoporosis
mineralocorticoid SEs incl hypertension, sodium and water retention and potassium loss
Cautions /contraindications corticosteroids
untreated systemic infection, avoid live virus vaccines in those receiving immunosuppressive doses
oral antidiabetic drugs
metformin and sulphonylureas
metformin mech of action
- activates AMP-kinase which is involved in metabolism of the membrane glucose transporter, GLUT4, and fatty acid oxidation
- inc gluc transport into cells, decreases hepatic gluconeogenesis and increases insulin sensitivity
indications metformin use
- first choice overweight pts in whom strict dieting has failed to control diabetes
- used in combo with sulphonylureas, pioglitazone, repaglinide, nateglinide or insulin if diabetes inadequately controlled
- improves fertility and weight reduction in pts with polycystic ovary syndrome
SEs metformin
anorexia nausea vom diarrhoea abdo pain metallic taste rarely type B (non hypoxic) lactic acidoses (mortality of 30-50%) B12 def (dec absorption) Hypoglycaemia doesn't usually occur with metformin
Cautions / contraindications metformin
contraindicated in severe renal impairment (eGFR
sulphonylureas mech of action
augment insulin secretion
indications sulphonylureas
pts w T2 DM not overweight or whom metformin contraindicated
diff types of sulphonylureas
glibenclamide
tolbutamide
gliclazide
glibeclamide
a sulphonylurea
long acting and associated with a greater risk of hypoglycaemia and should be avoided in the elderly
gliclazide and tolbutamide
sulphonylureas which are shorter acting that glibeclamide and a better choice
SEs sulphonylureas
mild and infrequent
GI disturbances
weight gain
sulphonylurea-induced hypoglycaemia may persist for many hours and must always be treated in hosp
occasionally cholestatic jaundice, hepatitis, allergic ski reactions and blood disorders
cautions and contraindications sulphonylureas
use short acting form in renal impairment
avoid in severe renal and hepatic impairment and in porphyria
contraindicated in breast feeding, and substitute insulin during pregnancy
treatment of hypoglycaemia
initially glucose 10-20g (2-4 teaspoons of sugar, 50-100mL fizzy drink) is given by mouth or in unconscious pt glucose or glucagon given by injection
mechanisms of action glucagon
glucagon mobilises glycogen stored in the liver
indications glucagon
acute hypogylcaemia where glucose cannot be given either by mouth or IV
SE glucagon
Nausea, vomiting, abdo pain, hypokalaemia, hypotension, hypersensitivity reactions
cautions/contraindications glucagon
phaeochromocytoma
what are lipid lowering drugs
statins
mechanism of action statins
inhibition of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, the rate limiting enzyme involved in cholesterol synthesis
more effective at lowering LDL-cholesterol than other classes of drugs but less effective than the fibrates in reducing triglycerides
indications statins
secondary prevention of coronary and CV events in pts w hx of angina or MI, PAD, non-haemorragic stroke, TIA
primary prevention of coronary events in pts at inc risk of CHD such as inherited dyslipidaemias or a 10y CV risk of 20% or more
egs statins
arvostatin and simvastatin
SEs statins
reversible myositis / myopathy - pts should report unexplained muscle pain, measure CK
altered liver biochemistry - liver biochem should be measured and within 3 months at 12 mo of starting
GI effects incl abdo pain, diarrhoea, flatulence, vomiting
Cautions / CI statins
Acute liver disease (acute viral hepatitis, alcoholic hepatitis), pregnancy, breast feeding and personal or fhx of muscle disorders
inc risk of myositis and rhabdomyolysis if statins are given with a fibrate, ezetimibe, ciclosporin, digoxin, warfarin, erythromycin and ketoconazole
