Pharm - tx of thyroid disorders Flashcards
indication for beta blockers
- adjunctive tx during thyroid storm
- to prep pts for surgery
- to manage pregnant pts w/ thyrotoxicosis in the short term
- primary therapy for thyroiditis or iodine-induced hyperthyroidism
beta blocker dosing
- propanolol 20-40 mg QID
- younger pts and severely toxic pts may require 240-280 mg/day in divided doses
- atenolol start w/ 25-50 mg/day and titrate up to 200 mg daily
contraindications to use of beta blockers
- decompensated heart failure
- asthma
- COPD
- concomitant MAOi or tricyclic antidepressant use
- 2nd or 3rd degree heart block
- bradycardia
- severe peripheral vascular dz
- Raynaud’s
goals of therapy of beta blockers
-decrease the sx of Grave’s
what are the 3 treatment options for Graves?
- antithyroid drugs (thioamides)
- radioidodine
- surgery
best tx options for pts w/ mild hyperthyroidism, minimal thyroid enlargement, and NO orbitopathy
- radioiodine (w/o thioamide pretreatment or glucocorticoids) OR
- 1-2 year course of thioamides
best tx options for pts w/ mild hyperthyroidism, minimal thyroid enlargement, and mild orbitopathy
- radioiodine (w/0 thioamide pretreatment but w/ glucocorticoids) OR
- 1-2 year course of thioamides
best tx options for pts w/ more severe hyperthyroidism
- consider definitive therapy w/ radioiodine or surgery OR
- 1-2 year course of thioamides OR
- long term thioamide therapy
best tx options for pts w/ moderate to severe orbitopathy
surgery rather than radioiodine w/ glucorcorticoids for definitive therapy
thioamide agents
- methimazole
- PTU (propylthiouracil)
goals of therapy for thioamide agents
- render the pt euthyroid as quickly and safely as possible
- usually within 3-8 weeks
Indication for thioamide agents
- preferred tx for children, pregnant women, and young adults with uncomplicated Grave’s disease
- to control hyperthyroidism (not a cure)
- can be given before surgery or RAI to deplete the thyroid gland of stored hormone to prevent thyroid storm
what are the two phases of dosing for thioamides
- initial therapy: achieve eurthyroidism
- maintenance therapy: continued until remission is achieved
methimazole dosing
- initial dose is based on the severity of the hyperthyroidism, size of goiter and free T4 level
- small goiter and mild disease (T4 1-1.5 ULN) can be started on 5-10 mg daily
- free T4 1.5 -2 times ULN can be started on 10-20 mg daily
- larger goiters and T4 2-3 times ULN should be started on 20-40 mg daily
monitoring parameters of methimazole
-monitor T3 and T4 for response to therapy
contraindications to methimazole
-first trimester of pregnancy (category D)
initial dosing of PTU
-300-600 mg in divided doses usually 3-4 times per day
monitoring parameters of PTU
monitor T3 and T4 for response to therapy
major adverse reactions to thioamides
- benign transient leukopenia
- agranulocytosis
- drug induced hepatotoxicity
indication for RAIU
- may be considered first choice given lower cost and lower risk of complication that surgery
- Poor surgical candidates, people who don’t response to drug therapy/had ADRs
- those who develop recurrent hyperthyroidism after surg
monitoring paramters for RAIU
measure free T4, total T3 and TSH 4-6 weeks after treatment and then at 4-6 week intervals for 6 months
goals of therapy for RAIU
to deplete thyroid hormone from gland→decreases risk of hyperthyroidism post-RAI administration and thyroid storm
Contraindications to RAIU
- pregnancy/lactating women
- severe/active Grave’s ophthalmopathy
- discouraged/prohibited in patients who can’t follow radiation precautions
Given a patient taking thioamides, select the appropriate monitoring for liver toxicity
- baseline CBC/liver enzymes
- routine liver function monitoring not recommended unless patient has hx of liver dz or is at increased risk for hepatitis
- question pt about sx of hepatitis during first few months of therapy
Given a patient taking thioamides, select the appropriate monitoring for agranulocytosis
- get baseline CBC
- Routine serial WBC not recommended
- Pts told to report following sx: rash, fever, sore throat, flu-like symptoms
- Differential WBC count ordered during febrile illness and at onset of pharyngitis
thyrotoxicosis factitia
Hyperthyroidism produced by the ingestion of exogenous thyroid hormone
long-term risks of hyperthyroidism
- results in negative calcium balance, reduced bone density, and increased fracture risk.
- tell patients to take 1200-1500mg Ca2+ daily through diet/supplements
given a pt with hypothyroidism or subclinical hypothyroidism, select the initial dose based on age, ideal body weight and concomitant conditions
- levothyroxine 1.6-1.7 mcg/kg/day
- ideal body weight is best predictor of daily requirements
- young healthy adults: start on full dose
- 50-60 yo w/o heart dz: start on 50 mcg/day
- odler w/ known cardiac dz: 12.5-25 mcg/day titrated up monthly
- subclinical: don’t need full dose: 25-75 mcg usually is enough
given a pregnant woman with thyroid disease, select the appropriate reasons to treat the disease
- Untreated maternal hypothyroidism can lead to increased rate of miscarriage, stillbirths, congenital defects, and mental retardation
- Thyrotoxic (hyperthyroidism) women need to be euthyroid before attempting surgery
appropriate treatment for hypothyroidism in pregnant women
- If they had it before pregnancy, increase levothyroxine dose by 25-30% upon a missed menstrual cycle or positive pregnancy test and notify their provider→increase from 7 doses/week to 9 doses/week
- All those with treated hypothyroidism who are planning a pregnancy should optimize thyroid status before conception (TSH <2.5mIU/L)
appropriate treatment for hyperthyroidism in pregnant women
- PTU is preferred for tx in first trimester
- Those on methimazole should be switched to PTU if pregnancy confirmed in first trimester→after first trimester, consider switching to methimazole
- Both cross the pacenta so to avoid deleterious effects on baby, maintain free T4 level at or just above the upper limits of normal→free T4 and TSH should be monitored every 2-6 weeks
goals of therapy for for hypothyroidism in pregnant women
- normalize serum TSH values within trimester-specific pregnancy range
- First trimester: 0.1-2.5 mIU/L
- Second trimester: 0.2-3.0 mIU/L
- Third trimester: 0.3-3.0 mIU/L
monitoring parameters for pregnant women
- Monitor TSH and total T4 should be monitored every 4 weeks during the first half of pregnancy
- TSH should be checked at least once between 26 and 32 weeks gestation
- Adjust doses as needed
Given a woman who is planning a pregnancy, select the appropriate reasons for correcting the thyroid status prior to conception
Untreated hypothyroidism can lead to increased rate of miscarriage, stillbirths, congenital defects and mental retardation
drugs that can cause drug-induced thyroid dz
- lithium
- amiodarone
- interferon-alpha
lithium
- inhibits release of thyroid hormone from gland so T4 and T3 fall, TSH rises
- can get lithium induced goiters
- most have family hx of thyroid dz/ positive thyroid abs
- ck baseline thyroid fxn before starting lithium
- ck every 6 mos
amiodarone
- has high iodine content so can get iodine induced hyperthyroidism
- can also get hypothyroidism
amiodarone induced hyperthyroidism
- occures suddenly
- leads to thyrotoxic sx
- labs: high thyroid hormone and low TSH
- type 1: related to iodine load
- type 2: direct destruction of thyroid cells
tx of type 1 amiodarone induced hyperthyroidism
- methimazole or PTU to block hormone synthesis
- potassium perchlorate may block iodine uptake by thyroid and deplete iodine stores
tx of type 2 amiodarone induced hyperthyroidism
- beta blockers for sx
- prednisone for anti-inflammatory action
amiodarone induced hypothyroidism
- not dose related
- lab findings: nl T4 and high TSH
- tx: T4 replacement
interferon alpha induced hyperthyroidism
- graves dz like and hyperthyroid thyroiditis
- d/t toxic effect on gland
- tx: beta blocker if sx are bothersome
interferon alpha induced hyporthyroidism
- risk factors: presence of antithyroid abs before tx, female, Asians
- more common than hyperthyroid
- tx: start T4 if sx warrant
