Users

Levothyroxine monitoring

Affected Drug

• H03AA01 Levothyroxine Sodium

Baseline

TSH / freeT4

Follow-up

TSH q6-12 weeks after dose change, annual once stable, add freeT4 if TSH outside of normal parameters or clinical suspicion that TSH does not accurately reflect the clinical status. More frequent TSH only if clinical suspicion of hyper or hypothyroidism. Elderly: Use with caution; decrease initial dose; suppressed TSH levels may increase risk of atrial fibrillation and mortality secondary to cardiovascular disease. *****Note: bioequivalence may vary between different brands*****

Important Interactions

• Drugs: C01BD01 Amiodarone
  Interaction May cause/worsen hyper/hypo thyroidism - measure TSH/fT4 q6-12 and dose adjust prn
• Drugs: Phenytoin
  Interaction monitor therapy after starting and with dose changes
• Drugs: Rifampin
  Interaction monitor therapy after starting and with dose changes
• Drugs: Sympathomimetics
  Interaction additive adrenergic events with increased risk of cardiac adverse events monitor clinically. Limited concern for OTC meds such as pseudoephedrine.

Details

Conditions	System	Monitoring		ADE	Incidence	Recommendation
		Baseline	Follow-up
	CVS	Hx/Px	PRN for signs & symptoms	htn, angina, mi, cardiac arrhythmias		Check TSH + fT4, adjust dose; decrease starting dose if elderly, Hx of IHD, or Hx of atrial fibrillation
	CNS	Hx /Px	Annual or prn	anxiety, fatigue, fever, headache, hyperactivity, insomnia, irritability		Check TSH +/- fT4 & adjust dose prn
	Dermatologic	Hx/Px	Annual or prn	anxiety, fatigue, fever, headache, hyperactivity, insomnia, irritability		Check TSH +/- fT4 & adjust dose prn
	GI	Hx/Px	PRN for signs & symptoms	decreased appetite, n/v/d, wt loss		Check TSH +/- fT4, adjust dose, consider other causes
	Hepatic	Hx/Px	PRN for signs & symptoms	increased lft’s		Check LFT’s if symptomatic, Check TSH +/- fT4, adjust dose prn, consider other causes
	Endocrine	Hx: DM/DI &adrenal insufficiency	PRN for signs & symptoms: PRN for signs & symptoms	fertility impaired, menstrual irregularities: symptoms of disease may be exaggerated or aggravated		Check TSH +/- fT4, adjust dose prn, consider other causes: Check TSH +/- FT4, adjust dose, consider other causes and adjust Tx other disease
	MSK	Hx /Px	Annual or prn	decreased bmd, muscle weakness, tremor		Check TSH +/- fT4, use lowest dose necessary for those at increased risk osteoporosis.
	Respiratory	Hx/Px	Annual or prn	dyspnea		Check TSH +/- fT4, adjust dose, consider other causes
	Miscellaneous	Hx/Px		diaphoresis, heat intolerance		Check TSH +/- fT4, adjust dose, consider other causes