Names and pronunciation
(proe-pill-thye-oh-yoor′a-sill) Prapyl-Thyracil
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Drug reference
(proe-pill-thye-oh-yoor′a-sill) Prapyl-Thyracil
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Func. class.: Thyroid hormone antagonist (antithyroid)
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Chem. class.: Thioamide
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ACTION: Blocks synthesis peripherally of T3, T4 (triiodothyronine, thyroxine), inhibits organification of iodine
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USES: Preparation for thyroidectomy, thyrotoxic crisis, hyperthyroidism, thyroid storm
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CONTRAINDICATIONS: Preg nancy, breastfeeding, hypersensitivity Precautions: Infants, bone marrow depression, fever, agranulocytosis, hepa- titis, jaundice
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Black Box Warning: Hepatic disease, pregnancy Black Box Warning: Hepatotoxicity: LFTs before, during treatment; jaundice, nausea, vomiting, abdominal pain, ano- rexia, diarrhea, fatigue • Fluids to 3-4 L/day unless contraindi- cated Black Box Warning: Pregnancy/breast- feeding: do not use in pregnancy, breast- feeding Black Box Warning: Pregnancy: to noti- fy prescriber immediately if pregnancy is planned or suspected; not to breastfeed
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SIDE EFFECTS CNS: Drowsiness, headache, vertigo, fever, paresthesias, neuritis GI: Nausea, diarrhea, vomiting, jaundice, hepatitis, loss of taste, liver failure, death GU: Nephritis HEMA: Agranulocytosis, leukopenia, thrombocytopenia, hypothrombinemia, lymphadenopathy, bleeding, vasculitis, periarteritis INTEG: Rash, urticaria, pruritus, alopecia, hyperpigmentation, lupuslike syndrome MS: Myalgia, arthralgia, nocturnal mus- cle cramps, osteoporosis
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INTERACTIONS • Bone marrow suppression: radiation, antineoplastics • Agranulocytosis: phenothiazines Increase: effects—potassium/sodium iodide, lithium Decrease: anticoagulant effect—hepa- rin, oral anticoagulants Drug/Lab Test Increase: PT, AST, ALT, alk phos
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DOSAGE AND ROUTES Thyrotoxic crisis • Adult/child: PO 200-400 mg q4hr for 1st 24 hr Preparation for thyroidectomy • Adult: PO 600-1200 mg/day • Child: PO 10 mg/kg/day in divided doses Hyperthyroidism • Adult: PO 100 mg tid increasing to 300 mg q8hr if condition is severe; continue to euthyroid state, then 100 mg daily tid P • Child >6 yr: PO 50 mg/day divided q8hr, titrate based on TSH/free T4 levels • Neonate (unlabeled): PO 5-10 mg/kg/ day in divided doses q8hr
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Available forms: Tabs 50, 100 mg
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Administer: • With meals to decrease GI upset • At same time each day to maintain product level • At lowest dose that relieves symptoms
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Assess: • Hyperthyroidism: weight loss, nervous- ness, insomnia, fever, diaphoresis, trem- ors; hypothyroidism: constipation, dry skin, weakness, headache; monitor T3, T4, which are increased; serum TSH, which is decreased; free thyroxine index, which is increased if dosage is too low; discontinue product 3-4 wk before RAIU • Pulse, B/P, temperature • I&O ratio; check for edema: puffy hands, feet, periorbits; indicates hypothy- roidism • Weight daily; same clothing, scale, time of day • Blood dyscrasias: CBC with differ- ential; leukopenia, thrombocytopenia, agranulocytosis; monitor periodically; agranulocytosis may develop in first 2 mo of treatment; discontinue treatment • Overdose: peripheral edema, heat in- tolerance, diaphoresis, palpitations, dys- rhythmias, severe tachycardia, increased temperature, delirium, CNS irritability • Hypersensitivity: rash, enlarged cervi- cal lymph nodes; product may have to be discontinued • Hypoprothrombinemia: bleeding, pete- chiae, ecchymosis • Clinical response: after 3 wk should include increased weight, pulse; de- creased T4 • Bone suppression: sore marrow throat, fever, fatigue
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Evaluate: • Therapeutic response: weight gain, de- creased pulse, decreased T4, decreased B/P
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CLINICAL CONSIDERATIONS
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Patient and caregiver information: • To take pulse daily • To report redness, swelling, sore throat, mouth lesions, which indicate blood dys- crasias; to report symptoms of hepatic dysfunction (yellow skin or eyes, clay- colored stools, dark urine) • To keep graph of weight, pulse, mood • To avoid OTC products that contain iodine • That seafood, other iodine products may be restricted • Not to discontinue product abruptly be- cause thyroid crisis may occur; about stress response • That response may take several months if thyroid is large • About the symptoms/signs of overdose: periorbital edema, cold intolerance, men- tal depression • About the symptoms of an inadequate dose: tachycardia, diarrhea, fever, irritability • To take medication as prescribed; not to skip or double dose; that missed doses should be taken when remembered up to 1 hr before next dose • To carry emergency ID listing condi- tion, medication
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PHARMACOKINETICS Onset up to 3 wk, peak 6-10 wk, duration 1 wk to 1 mo, half-life 1-2 hr; excreted in urine, bile, breast milk; crosses placenta; concentration in thyroid gland
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• Adult/child: PO 200-400 mg q4hr for 1st 24 hr Preparation for thyroidectomy
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• Adult: PO 600-1200 mg/day
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• Adult: PO 100 mg tid increasing to 300 mg q8hr if condition is severe; continue to euthyroid state, then 100 mg daily tid P
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