Thyroid Disorders - Classes of medication
Thyroid Agents (HYPOthyroid) |
Levothyroxine (T4)
Synthroid® OR Eltroxin® |
Synthetically made T4 hormone (body then converts to T3 in peripheral tissues as needed)
Identical to endogenously made T4
All adverse effects are rare
May see signs of HYPERthyroidism with doses too high
Dosed according to body weight, then adjusted according to TSH levels
Takes 1-3 weeks for full therapeutic benefit |
Other thyroid products |
Liothyronine (synthetic T3)
Desiccated thyroid (mixture of T3 & T4 obtained from dried thyroid glands of pigs)
Both products have been largely replaced by levothyroxine |
Anti-thyroid Agents (HYPERthyroid) |
Propylthiouracil |
Inhibits synthesis of thyroid hormone, as well as conversion of T4 -> T3
Used to control thyroid function until surgery (short-term) |
Methimazole |
Inhibits synthesis of thyroid hormone, but does NOT inhibit conversion of T4 -> T3
Safer than propylthiouracil, but takes longer to work (could be months)
Taken once a day
A long-term option if patient has opted out of surgery |
Radioactive iodide |
Iodine is taken up by only the thyroid
Radioactivity destroys the thyroid gland – attempt to only destroy some of it, but many result in HYPOthyroid state
Once/if they are HYPOthyroid, we replace thyroid hormone (likely levothyroxine)
Can also treat thyroid cancer – there have been no known cases of cancer caused by 131I
2/3 of patients respond to one treatment – used when opposed to surgery
Can take 3-6 months after 1 dose (3 months between doses)
Tissue damage limited to thyroid gland only with no surrounding structures affected |
Adverse effects
Levothyroxine |
All adverse effects are rare
May see signs of HYPERthyroidism with doses too high
Avoid with minerals such as calcium, magnesium, aluminum – blocks absorption – separate by 2h |
Propylthiouracil (PTU) |
rash, symptoms of HYPOthyroidism, agranulocytosis, hepatotoxicity, many drug interactions (anticoagulants, digoxin)
Must be taken multiple times a day (short t½)
Can take up to 3 weeks to exert effect (does not affect hormone already released) |
Metformin |
nausea (take with food), diarrhea (transient), lactic acidosis (rare) |
Sulfonylureas |
hypoglycemia, weight gain, nausea, rash, hepatotoxicity (don’t take with alcohol)
Can cause hypoglycemia on its own (most likely of all classes besides insulin)
Avoid in elderly (more susceptible to hypoglycemia) |
Replaglinide |
hypoglycemia (less than sulfonylureas), weight gain
Generally only cause hypoglycemia when combined with another hypoglycemic drug |
Thiazolidinediones |
edema and fluid retention, headache, weight gain
Post-marketing surveillance: may increase risk of fractures, concern about ↑ cardiovascular events
Not likely to cause hypoglycemia on its own |
Acarbose |
abdominal cramping, diarrhea, flatulence, malabsorption of vitamins/minerals or other drugs (separate by 2h); potential hepatotoxicity
Does not cause hypoglycemia on its own
IF hypoglycemic, and need to give sugar, must take glucose tabs, milk, or honey; NOT SUCROSE |
DPP4 Inhibitors |
hypoglycemia, cough, nasopharyngitis, rash, hypersensitivity, muscle aches, joint pain
Not likely to cause hypoglycemia on its own
Rare: pancreatitis (severe abdominal pain that may be accompanied by vomiting)
Oral tablets taken once daily |
GLP-1 Agonists |
nausea, diarrhea, hypoglycemia, infusion site reactions, pain in stomach area, decreased appetite, indigestion, burping, flatulence, joint and muscle pain, dizziness, headache, cough, rash, pancreatitis, dehydration, increases in heart rate
Can cause hypoglycemia on its own
Rare: anaphylactic reaction, nephrotoxicity, thyroid cancer |
SGLT-2 Inhibitors |
weight loss, diuretic effect, hypotension, polydipsia (thirst), increased rate of urinary tract infections, must have adequate kidney function
Not likely to cause hypoglycemia on its own |
Corticosteroids Local Administration adverse effects |
Opthalmic |
Stinging, redness, tearing, burning, secondary infection
Long-term: cataracts, glaucoma |
Oral Inhalation |
Thrush, hoarseness, dry mouth, dysphoria (change in voice), dysphagia (difficulty swallowing), taste disturbance |
Nasal Inhalation |
Rhinorrhea, burning, sneezing, dry mucous membranes, epistaxis, loss of smell |
Topical |
Burning, irritation, skin atrophy (thinning of skin), telangiectasia ()
To Prevent: lowest dose possible, shortest duration possible, applying very thin layer of product only on affected area, do not apply to open skin |
Adverse Effects of Corticosteroids Systemic Administration |
CNS |
euphoria, insomnia, restlessness, increased appetite, altered mood (depression, mania, psychosis) |
Eye |
cataracts, glaucoma |
Face/Trunk |
redistribution of fat -> moon face, buffalo hump, protruding abdomen |
Heart |
hypertension, enlarged heart |
GI |
stomach upset, may ↑ risk of ulcer |
Blood |
glucose intolerance -> diabetes; leukocytosis |
Kidneys |
fluid & water retention (if mineralocorticoid activity) |
Growth inhibition |
use in kids only if necessary (inhalers safe) |
Muscle |
wasting of muscle tissue (myopathy) |
Bones |
osteoporosis |
Skin |
easy bruising, poor wound healing, acne, striae |
Prednisone |
nausea, hypertension, hyperglycemia, insomnia, psychosis, redistribution of fat, osteoporosis, easy bruising, edema, infections, HPA-axis suppression |
Contraception – Adverse Effects |
Estrogen |
Nausea, Breast tenderness, Headache, Bloating, Thrombosis |
Progestin |
Irritability, Fatigue, Breast tenderness, Bloating, Withdrawal bleeding (cyclical), Headache, Adverse lipid alterations, “PMS-like symptoms” |
Emergency Contraception |
Nausea – if vomit within 2 hours of dose – take dose again; may give with anti-emetic (dimenhydrinate – Gravol®)
Irregular bleeding – spotting after taking dose; regular menses may be off by a few days (early or late)
Abdominal pain, cramping – use acetaminophen (not NSAID in case of pregnancy)
Diarrhea, breast tenderness, fatigue, headache – all possible and transient |
α1-Blockers |
Retrograde ejaculation, Dizziness, fatigue, rhinitis, Orthostatic hypotension, Syncope “first-dose syncope” |
α-reductase Inhibitors |
Ejaculatory dysfunction, Loss of libido, Impotence, Gynecomastia, )All effects due to ↓ DHT levels) Can cause birth defects in male children |
PDE-5 Inhibitors |
: hypotension, headache, back and muscle pain, hearing loss, visual changes, priapism (erection > 4h) |
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Classes of Oral Hypoglycemics
Metformin |
A biguanide (only one in it’s class)
Mechanism: Enhances tissue sensitivity to insulin -> reducing insulin resistance, Also decreases hepatic gluconeogenesis
Often first drug prescribed |
Sulfonylureas
Glyburide, gliclazide, glimepiride |
Enhance insulin secretion from the pancreas (aka insulin secretagogue)
Also increase insulin sensitivity at target tissues (like metformin) |
Repaglinide |
A meglitinide
Stimulate release of insulin from pancreas (insulin secretagogue)
Requires presence of glucose to exert action, therefore MUST BE TAKEN BEFORE (within 30 mins) OR WITH A MEAL |
Thiazolidinediones
Rosiglitazone, pioglitazone |
Enhance insulin sensitivity at target tissues (similar to metformin)
Food has no direct effect (can be taken with or without food) |
Acarbose |
Inhibits α–glucosidase, which reduces the rate of absorption of carbohydrates from the GI tract, preventing hyperglycemia – therefore TAKE WITH MEALS |
Dipeptidyl Dipeptidase 4 (DPP4) inhibitors
linagliptin, alogliptin, sitigliptin, saxagliptin |
Incretins are a group of hormones that tell the pancreas to release insulin (from pituitary); basal rate and elevated in response to food
Drugs particularly target glucagon-like peptide 1 (an incretin) and others
DPP-4 inhibitors inhibit the breakdown of incretins, which increases and prolongs their activity -> instructs pancreas to release more insulin for longer |
Glucagon-like peptide 1 (GLP-1) agonists
exenatide, liraglutide, dulaglutide, semaglutide, lixisenatide |
GLP-1 agonists mimic endogenous GLP-1 (an incretin)
Results in increased satiety, reduced gastric emptying, and greater insulin secretion
GLP-1 agonists are resistant to degradation by DPP4 enzymes
Given as SC injections
1st Gen are administered daily or BID; 2nd Gen are weekly
Varying t ½ of 2.4 hours - 2 weeks |
SGLT-2 Inhibitors
Canagliflozin, dapagliflozin, empagliflozin, ertugliflozin |
Increases excretion of glucose in the kidney by preventing glucose reabsorption, therefore reducing blood glucose levels |
Diabetes medications and treatments
Glucose homeostasis factors |
Insulin |
Released in response to HIGH blood sugar
Promotes the uptake, utilization, and storage of glucose → lowers blood glucose concentration
Suppresses endogenous glucose and Inhibits glucagon release
Causes rapid uptake, storage, and use of glucose by insulin sensitive tissues (Muscle, liver, adipose (fat), brain) |
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Basal release rate of 0.5 – 1.0 unit / hour |
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Rate of release increases when blood glucose (BG) > 5.5mmol/L (in response to eating - bolus) |
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Usual secretion: 25-50 units / day |
Glucagon |
Released in response to LOW blood sugar
Increases the hepatic glucose output → increases blood glucose concentration |
Diabetes Mellitus |
A metabolic disorder characterized by the presence of hyperglycemia due to defective insulin secretion, insulin action, or both |
Type 1 |
due to defective insulin secretion
An autoimmune destruction of pancreatic β–cells, causing an absolute lack of insulin secretion |
Type 2 |
due to insulin resistance, eventually leading to defective insulin secretion |
Hyperglycemia |
HYPERglycemia would occur if a patient did not have enough insulin
FPG > 7.0mmol/L |
Hypoglycemia |
HYPOglycemia would occur if: too much insulin, improper timing of insulin, or patient skipped a meal
FPG < 4mmol/L |
Insulin Treatment |
Insulin preparations vary by:
Onset of action, Time to peak glycemic effect, Duration of action, Appearance |
Long-Acting Insulin Analogues (LAIA) |
Insulin detemir (Levemir) |
After injection, the molecules self-associate and bind to albumin slowly released from subcutaneous tissue into blood stream at a slow, predictable rate |
Insulin degludec (Tresiba) |
Forms multihexamers following SC injection, leading to a depot delayed absorption from SC tissue and also binding to albumin leads to longer time profile |
Insulin glargine (Lantus) |
An acidic (pH of 4) product in the vial, and once injected subcutaneously, the acidic solution is neutralized, and forms micro-precipitates these slowly dissolve over at a slow, predictable rate |
Insulin Routes of Administration |
Subcutaneously |
most common |
With an insulin pump |
continuous subcutaneously |
Inhaled dry powder |
not yet approved in Canada |
Intravenous |
only regular (R or Toronto) for emergencies |
Mixing Insulins |
Important note regarding administration: not all insulins can be mixed
ALWAYS CHECK |
R/Toronto + N/NPH |
may be pre-mixed and stored together |
RAIA + N/NPH |
may mix, but administer immediately (do not store mixed) |
LAIA |
do not mix in same syringe with any other insulins – due to specific mechanism of action and pH |
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