pharm wk 6 Flashcards
what to do in patient with thyroid nodules
Recognize which patients with thyroid nodules require fine needle biopsy for cytologic diagnosis versus observation
thyrotoxicosis vs hyperthyroid vs thyroid storm
Thyrotoxicosis is any condition of excessive thyroid hormone and its effects
Hyperthyroidism is specifically due to excess thyroid hormone production
Thyroid storm if a life-threatening medical emergency caused by severe thyrotoxicosis
causes of thyrotoxicosis
graves disease, toxic nodules, iodine excess, and TSH-producing pituitary adenomas, among others
non pharmalogical choices for hyperthyroid
Important to consider surgery as an option given the limitations of medication and the potential for the formation of goitre
Hypothyroidism is a common and likely adverse effect thyroid surgery
what is the form of radioactive iodine used
iodine 131
what is iodine 131 used in
Used to ablate thyroid tissue in patients with Graves disease and toxic nodules
The thyroid rapidly concentrates iodine, so an oral dose has minimal effect on the rest of the body
Beta wave emission destroys surrounding tissue within a range of 0.6 – 2 mm
adverse effects of using radioactive iodine (iodine 131 to kill tissue in graves and toxic nodules)
High risk of hypothyroidism
Possible worsening of Graves orbitopathy
Risk of radiation thyroiditis
what does methimazole do ? what does it effect? what does it not effect?
Decreases the production of thyroid hormone
Interferes with iodination of tyrosine as well as with coupling
Does not affect stored thyroid hormone or thyroid hormone in circulation
adverse effects of methimazole
Risk of skin rash, allergic reaction, and agranulocytosis
Can cause hepatotoxicity in rare instances
Contraindicated during the first trimester of pregnancy due to causing aplasia cutis
what can methimazole cause in pregnancy
aplasia cutis
Contraindicated during the first trimester of pregnancy due to causing aplasia cutis
what is an example of beta blockers
propanolol
what is the thyroid hormone given in hypothryoid
levothyroxine
what are the 2 antithyroid agents
methimazole and propylthiouracil
PROPYLTHIOURACIL is similar to what
methimazole
what do propylthiouracil do
Similar mechanism of action to methimazole
Has the additional action of inhibiting the conversion of T4 to T3 in the periphery
Affects production of thyroid hormone and existing thyroid hormone
adverse effects of propylthiouracil
Similar adverse effects to methimazole
Risk of skin rash, allergic reaction, and agranulocytosis
Can cause severe hepatotoxicity that may be fatal in rare instances
Does not cause aplasia cutis
METHIMAZOLE VS PROPYLTHIOURACIL
a. in most instances?
b. in breastfeeding and kids?
c. 1st trimester pregnancy?
d. thyroid storm treatment?
m
m
p
p
Methimazole is the preferred drug in most instances due to the lower risk of causing hepatotoxicity
Methimazole is the preferred drug while patients are breastfeeding and in children
Propylthiouracil is the preferred drug during the first trimester of pregnancy
Propylthiouracil can be used to treat thyroid storm as it affects thyroid conversion in the periphery
what to use for thyroid storm
Propylthiouracil
what to use in 1st trimester of pregnancy
Propylthiouracil
what has a lower risk of hepatotexocithy ; METHIMAZOLE VS PROPYLTHIOURACIL
METHIMAZOLE
what do beta blockers not effect
thyroid hormone production
what do beta blockers effect
Used to ameliorate the symptoms of adrenergic excess caused by excess thyroid hormone (elevated heart rate, hypertension, etc.)
propanolol (beta blocker) can decrease what
Propranolol can decrease the conversion of T4 to T3 in the periphery
adverse effects of beta blockers/ propanolol
Bradycardia, dizziness, fatigue, headache, hypotension.
Avoid in patients with asthma or conditions associated with bradycardia; taper once thyrotoxicosis improves.
who should not take propanolol/ beta blocker
patients with asthma or conditions associated with bradycardia; taper once thyrotoxicosis improves.
what is common vs uncommon cause of hypothyroid
Rarely caused by iodine deficiency in North America
Most commonly caused by Hashimoto’s thyroiditis
what is the standard treatment for hypothryoid
levothyroxine
what is levothyroxine
Replacement therapy – essentially treatment using orally administered T4
how long does it take to get to a steady state with levothyroxine
Takes 6 weeks to attain a new steady state after dosage adjustments
wait 6 weeks to adjust dose
what is levothyroxine dosing based on
Generally based on lean body mass
Elderly patients may need less
For those at risk of angina start lower
dosing of levothyroxine depends on
depending on endogenous thyroid function
In patients with an intact thyroid or with mild or subclinical disease much smaller initial dosages may be needed (25 – 50 mcg)
In patients with negligible thyroid function full replacement dosages may be needed
interactions of levothyroxine
Absorption may be reduced by antacids and mineral supplementation
Proton pump inhibitors and estrogens may interfere with absorption
Variable effects with anticoagulant drugs
Separate administration by 6 hours
Levothyroxine is typically taken first thing in the morning before any other medications
adverse effects of levothyroxine
Symptoms of hyperthyroidism if overtreated
Possible exacerbation of angina
Glycemic control may decline with initiation of levothyroxine, potentially necessitating dosage adjustment of antihyperglycemic agents
what is desiccated thyroid
Tablets contain T4 and T3 in fixed amounts
thyroid hormone pill made from animal thyroid gland
adverse effects of desiccated thyroid
Similar to levothyroxine
Risk of cardiovascular and neurological adverse effects increases with larger doses (due to T3)
- palpitation, tachycardia, cardiac arrhythmias, angina pectoris - nervousness, tremors, headache, insomnia
- sweating, heat intolerance, fever, weight loss
what added risk does desiccated thyroid have compared to levothyroxine
CVD and neurological bc of the T3
typical dose calculation for levothyroxine
1.6 x weight in kg
but also take into account BMI, TSH level, symptoms, age, etc
A patient returns for follow-up 6 weeks after receiving their first prescription for levothyroxine and their TSH value remains unchanged. The patient reports taking it every morning with the iron supplement they were also prescribed. Which of the following is the best course of action?
A. Increase the dose of levothyroxine by 12.5 mcg
B. Reduce the dose of levothyroxine by 12.5 mcg
C. Switch the patient to an equivalent dose of desiccated thyroid
D. Change the time the patient takes their iron supplement
D. Change the time the patient takes their iron supplement
what affects levothyroxine absorption
antacids and mineral supplements
take separately
DOSING FOR THYROID MED CASES
