Mosby's 2014 Nursing Drug Reference (260 page)

methimazole (Rx)

(meth-im′a-zole)

Tapazole

Func. class.:
Thyroid hormone antagonist (antithyroid)

Chem. class.:
Thioamide

Do not confuse:
methimazole
/metoprolol/minoxidil

ACTION:

Inhibits synthesis of thyroid hormones by decreasing iodine use in manufacture of thyroglobin and iodothyronine; does not affect circulatory T
4
, T
3

USES:

Hyperthyroidism, preparation for thyroidectomy, thyrotoxic crisis; thyroid storm when PTU is contraindicated

CONTRAINDICATIONS:

Pregnancy (D), breastfeeding, hypersensitivity

Precautions:
Infection, bone marrow suppression, hepatic disease, bleeding disorders

DOSAGE AND ROUTES
Calculator
Hyperthyroidism

• Adult:
PO
15 mg/day (mild hyperthyroidism); 30-40 mg/day (moderate to severe); 60 mg/day (severe); maintenance 5-15 mg/day; may be divided

• Child:
PO
0.4 mg/kg/day in divided doses q8hr; continue until euthyroid; maintenance dose 0.2 mg/kg/day in divided doses q8hr, max 30 mg/24 hr; may be divided

Preparation for thyroidectomy

• Adult and child:
PO
same as above; iodine may be added × 10 days before surgery

Thyrotoxic crisis

• Adult and child:
PO
same as hyperthyroidism with iodine and propranolol

Available forms:
Tabs 5, 10, 15, 20 mg

Administer:

• 
With meals to decrease GI upset

• 
At same time each day to maintain product level

• 
Lowest dose that relieves symptoms; discontinue before RAIU

SIDE EFFECTS

CNS:
Drowsiness, headache, vertigo, fever
, paresthesias, neuritis

ENDO:
Enlarged thyroid

GI:
Nausea, diarrhea, vomiting
,
jaundice, hepatitis,
loss of taste

GU:
Nephritis

HEMA:
Agranulocytosis, leukopenia, thrombocytopenia, hypothrombinemia, lymphadenopathy,
bleeding, vasculitis

INTEG:
Rash, urticaria, pruritus, alopecia, hyperpigmentation
, lupuslike syndrome

MS:
Myalgia, arthralgia, nocturnal muscle cramps

PHARMACOKINETICS

Onset 12-18 hr; duration 36-72 hr; half-life 4-12 hr; excreted in urine, breast milk; crosses placenta

INTERACTIONS

Increase:
bone marrow depression—radiation, antineoplastic agents

Increase:
response to digoxin

Decrease:
effectiveness—amiodarone, potassium iodide

Decrease:
Anticoagulant effect—warfarin

Drug/Lab Test

Increase:
PT, AST, ALT, alk phos

NURSING CONSIDERATIONS
Assess:

• 
Hyperthyroidism:
palpitation, nervousness, loss of hair, insomnia, heat intolerance, weight loss, diarrhea

• 
Hypothyroidism:
constipation, dry skin, weakness, fatigue, headache, intolerance to cold, weight gain; adjustment may be needed

• 
Pulse, B/P, temp

• 
I&O ratio; check for edema: puffy hands, feet, periorbits; these indicate hypothyroidism

• 
Weight daily; same clothing, scale, time of day

• 
T
3
, T
4
, which are increased; serum TSH, which is decreased; free thyroxine index, which is increased if dosage too low; discontinue product 3-4 wk before RAIU

 
Blood dyscrasias:
CBC, leukopenia, thrombocytopenia, agranulocytosis; if these occur, product should be discontinued and other treatment initiated, may occur at higher doses

• 
Hypersensitivity:
rash, enlarged cervical lymph nodes; product may have to be discontinued

• 
Hypoprothrombinemia:
bleeding, petechiae, ecchymosis

• 
Clinical response:
after 3 wk should include increased weight; decreased T
4
, pulse

 
Bone marrow suppression:
sore throat, fever, fatigue

Perform/provide:

• 
Storage in light-resistant container

• 
Increased fluids to 3-4 L/day unless contraindicated

Evaluate:

• 
Therapeutic response: weight gain, decreased pulse, decreased T
4
, B/P

Teach patient/family:

• 
Not to breastfeed

• 
To take pulse daily

• 
To report redness, swelling, sore throat, mouth lesions, fever, which indicate blood dyscrasias

• 
To keep graph of weight, pulse, mood

• 
To avoid OTC products, seafood that contains iodine, other iodine products

• 
Not to discontinue product abruptly because thyroid crisis may occur; stress patient response

• 
That response may take several months if thyroid is large

• 
Symptoms and signs of overdose:
periorbital edema, cold intolerance, mental depression

• 
Symptoms of inadequate dose:
tachycardia, diarrhea, fever, irritability

• 
To take medication as prescribed; not to skip or double dose

Canada only   Side effects:
italics
= common;
bold
= life-threatening   
Nurse Alert

HIGH ALERT
methotrexate (Rx)

(meth-oh-trex′ate)

Rheumatrex, Trexall

Func. class.:
Antineoplastic-antimetabolite (vesicant)

Chem. class.:
Folic acid antagonist

Do not confuse:
methotrexate
/metolazone/mitoXANtrone

ACTION:

Inhibits an enzyme that reduces folic acid, which is needed for nucleic acid synthesis in all cells; specific to S phase of cell cycle; immunosuppressive

USES:

Acute lymphocytic leukemia; in combination for breast, lung, head, neck carcinoma; lymphosarcoma, gestational choriocarcinoma, hydatidiform mole, psoriasis, RA, mycosis fungoides, osteosarcoma

Unlabeled uses:
Burkitt’s lymphoma, bladder or ovarian cancer, carcinomatous meningitis, desmoid tumor, fibromatosis, asthma, active Crohn’s disease, ulcerative colitis, GVHD prophylaxis, ectopic pregnancy, pregnancy termination, psoriatic arthritis, pruritus due to cholestasis or primary biliary cirrhosis, SLE, sarcoidosis

CONTRAINDICATIONS:

Hypersensitivity, leukopenia (<3500/mm
3
), thrombocytopenia (<100,000/mm
3
), anemia; psoriatic patients with severe renal disease, alcoholism, HIV

 

Black Box Warning:

Pregnancy (X), hepatic disease

Precautions:
Breastfeeding, children

 

Black Box Warning:

Renal disease, ascites, diarrhea, exfoliative dermatitis, infection, intrathecal administration, lymphoma, pleural effusion, pulmonary disease, radiation therapy, stomatitis, tumor lysis syndrome, renal impairment

DOSAGE AND ROUTES
Calculator
Acute lymphocytic leukemia

• Adult and child:
PO/IM/IV
3.3 mg/m
2
/day × 4-6 wk until remission then 20-30 mg/m
2
PO/IM
weekly in 2 divided doses or 2.5 mg/kg
IV
× 2 wk

Choriocarcinoma

• Adult and child:
PO/IM
15-30 mg/day × 5 days then off 1 wk; may repeat

Meningeal leukemia

• Adult and child:
12 mg/m
2
INTRATHECALLY
q2-5days until CSF is normal then 1 additional dose, max 15 mg

Lymphosarcoma (stage III)

• Adult:
PO/IM/IV
0.625-2.5 mg/kg/day

Osteosarcoma

• Adult and child:
IV
12 g/m
2
given over 4 hr then leucovorin rescue

Mycosis fungoides

• Adult:
PO
5-50 mg q wk or 15-37.5 mg twice weekly;
IV/IM
50 mg q week or 15-37.5 mg twice weekly

Psoriasis

• Adult:
PO/IM/IV
10-25 mg/wk or 2.5 mg
PO
q12hr × 3 doses/wk, may increase to 25 mg/wk

Breast cancer

• Adult:
IV
40-60 mg/m
2
on day 1 of every 21-28 days with other antineoplastics

Epidermal head/neck cancer

• Adult/child:
IV
40 mg/m
2
on days 1 and 15, q21days alone or in combination with bleomycin, CISplatin

• Adult:
PO
25-50 mg/m
2
q7days

• Child:
PO
7.5-30 mg/m
2
q7-14days

Rheumatoid arthritis

• Adult:
PO
7.5 mg/wk or in divided doses of 2.5 mg q12hr × 3 given per wk; max 20 mg/wk

Polyarticular-course juvenile RA

• Child:
PO/IM
10 mg/m
2
/wk

Burkitt’s lymphoma (stages I, II, III)

• Adult/adolescent/child:
IV
200 mg/m
2
days 8 and 15 q21days with bleomycin, cyclophosphamide, vinCRIStine, dexamethasone

Bladder cancer (unlabeled)

• Adult:
IV
30 mg/m
2
on days 1, 15, 22 q28days in combination with vinBLAStine, DOXOrubicin, CISplatin (MVAC) regimen

Active crohn’s disease/ulcerative colitis (unlabeled)

• Adult:
IM
25 mg/wk;
SUBCUT
15 mg/kg/wk × 16 wk

GVHD prophylaxis (unlabeled)

• Adult and child:
IV
15 mg/m
2
on day 1 after transplant then 10 mg/m
2
on days 3, 6, 11

Ectopic pregnancy (unlabeled)

• Adult:
IM
50 mg/m
2
may be used in combination with mifepristone

Pregnancy termination prior to 63rd day of pregnancy (unlabeled)

• Adult:
IM
50 mg/m
2
then intravaginal misoprostol 5-7 days later

Psoriatic arthritis (unlabeled)

• Adult:
PO
5-7.5 mg weekly

Available forms:
Tabs 2.5, 5, 7.5, 10, 15 mg; inj 25 mg/ml; powder for inj 1 g

Administer:

• 
Using chemotherapeutic handling

• 
Antiemetic 30-60 min before product

• 
Allopurinol or sodium bicarbonate to maintain uric acid levels, alkalinization of urine (pH >7.5), adequate fluids

Direct IV route

• 
After diluting 5 mg/2 ml of sterile water for inj; give through
Y
-tube or 3-way stopcock

Intermittent/Continuous IV INF route

• 
Further dilute in D5W, D5NS, NS, prior to infusion check patency of vein, flush with 5-10 ml of D5W, NS, infuse at 4-20 mg/hr or prescribed rate

 
Leucovorin rescue:
leucovorin calcium within 24 hr of product to prevent tissue damage; check agency policy, continue until methotrexate level <10
−8
m

IV INF intermediate or high dose (500 mg/m
2
over <4 hr or >1 g/m
2
over >4 hr):
confirm WBC >1500/mm
3
, neutrophils >200/mm
3
, platelets >75,000/mm
3
, serum bilirubin <1.2 mg/dl, serum creatinine WNL, SGPT <450 U, creatinine clearance >60 ml/min

 
Give sodium bicarbonate tabs or IV fluids to prevent precipitation of product at high doses; urine pH should be >7; may need to reduce dosage if BUN 20-30
mg/dl or creatinine is 1.2-2 mg/dl; stop product if BUN >30 mg/dl or creatinine >2 mg/dl

Additive compatibilities:
Cephalothin, cyclophosphamide, cytarabine, fluorouracil, hydrOXYzine, mercaptopurine, ondansetron, sodium bicarbonate, vinCRIStine

Solution compatibilities:
Amino acids, 4.25%/D
25
, D
5
W, sodium bicarbonate 0.05 mol/L, sodium chloride 0.9%

Syringe compatibilities:
Bleomycin, CISplatin, cyclophosphamide, doxapram, DOXOrubicin, fluorouracil, furosemide, heparin, leucovorin, mitoMYcin, vinBLAStine, vinCRIStine

Y-site compatibilities:
Allopurinol, amifostine, amphotericin B cholesteryl, asparaginase, aztreonam, bleomycin, cefepime, cefTRIAXone, cimetidine, CISplatin, cyclophosphamide, cytarabine, DAUNOrubicin, dexchlorpheniramine, diphenhydrAMINE, DOXOrubicin, DOXOrubicin liposome, etoposide, famotidine, filgrastim, fludarabine, fluorouracil, furosemide, gallium, ganciclovir, graniset-ron, heparin, HYDROmorphone, imipenem-cilastatin, leucovorin, LORazepam, melphalan, mesna, methylPREDNISolone, metoclopramide, mitoMYcin, morphine, ondansetron, oxacillin, PACLitaxel, piperacillin/tazobactam, prochlorperazine, ranitidine, sargramostim, teniposide, thiotepa, vinBLAStine, vinCRIStine, vinorelbine

Intrathecal route

 

Black Box Warning:

Use preservative-free sol, reconstitute with NS; dose should be drawn into 5- to 10-ml syringe after LP, vol of CSF should be withdrawn equal to vol of methotrexate; allow CSF to flow into syringe and mix, inject over 15-30 sec with bevel of needle upward

SIDE EFFECTS

CNS:
Dizziness,
seizures, leukoencephalopathy,
headache, confusion,
encephalopathy,
hemiparesis, malaise, fatigue, chills, fever;
arachnoiditis
(intrathecal)

EENT:
Blurred vision, optic neuropathy

GI:
Nausea, vomiting, anorexia, diarrhea, ulcerative stomatitis
,
hepatotoxicity,
cramps, ulcer, gastritis,
GI hemorrhage,
abdominal pain, hematemesis,
hepatic fibrosis, acute toxicity

GU:
Urinary retention,
renal failure,
menstrual irregularities, defective spermatogenesis,
hematuria, azotemia, uric acid nephropathy

HEMA:
Leukopenia, thrombocytopenia, myelosuppression, anemia

INTEG:
Rash, alopecia
, dry skin, urticaria, photosensitivity, folliculitis, vasculitis, petechiae, ecchymosis, acne, alopecia,
severe fatal skin reaction

RESP:
Methotrexate-induced lung disease

SYST:
Sudden death,
Pneumocystis jiroveci
,
tumor lysis syndrome

PHARMACOKINETICS

Not metabolized; excreted in urine (unchanged); crosses placenta, blood-brain barrier; 50% plasma protein bound; terminal half-life 10-12 hr

PO:
Readily absorbed

PO/IM/IV:
Onset, duration unknown

IT:
Onset, peak, duration unknown

INTERACTIONS

Do not use with proton pump inhibitors

Increase:
toxicity—salicylates, sulfa products, other antineoplastics, radiation, alcohol, probenecid, NSAIDs, phenylbutazone, theophylline, penicillins

Increase:
hypoprothrombinemia—oral anticoagulants

Increase:
hepatitis—acitretin, avoid concurrent use

Decrease:
effect of oral digoxin, vaccines, phenytoin, fosphenytoin

Decrease:
effect of methotrexate—folic acid supplements

NURSING CONSIDERATIONS
Assess:

• 
Make sure product is taken weekly in RA, JRA

 

Black Box Warning:

Infection:
those with active infections should be treated for infection before product use; monitor temperature, fever may indicate beginning of infection

• 
Make sure drug-drug interacting products are discontinued before therapy, and do not resume until methotrexate level is safe

 
CBC, differential, platelet count weekly; avoid use until WBC is >1500/mm
3
or platelet count is >75,000/mm
3
, neutrophils >200/mm
3
; notify prescriber; WBC, platelet nadirs occur on day 7; monitor

 

Black Box Warning:

Renal disease:
avoid use in renal failure, BUN, serum uric acid, urine CCr, electrolytes before, during therapy; I&O ratio; report fall in urine output to <30 ml/hr

• 
Bleeding time, coagulation time during treatment; bleeding: hematuria, guaiac, bruising, or petechiae in mucosa or orifices

• 
Effects of alopecia on body image; discuss feelings about body changes

 

Black Box Warning:

Pulmonary toxicity:
those with ascites or pleural effusion at greater risk for toxicity; fluid should be removed before treatment; monitor plasma methotrexate levels

 

Black Box Warning:

Tumor lysis syndrome:
hyperkalemia, hyperphosphatemia, hyperuricemia, hypocalcemia, decreased urine output; use aggressive hydration, allopurinol to correct severe electrolyte imbalances, renal toxicity

 

Black Box Warning:

Hepatotoxicity:
jaundiced skin and sclera, dark urine, clay-colored stools, pruritus, abdominal pain, fever, diarrhea, hepatic studies before and during therapy: bilirubin, alk phos, AST, ALT; liver biopsy should be done before start of therapy (psoriasis)

• 
Monitor methotrexate levels, adjust leucovorin dose based on level

• 
Buccal cavity for dryness, sores, ulceration, white patches, oral pain, bleeding, dysphagia

 

Black Box Warning:

Serious skin reaction:
Stevens-Johnson syndrome, exfoliate dermatitis, skin necrosis, erythema multiform may occur within days of receiving product by any route, product should be discontinued

• 
Strokelike encephalopathy:
common in high-dose therapy; assess for confusion, hemiparesis, seizures, coma; usually transient

• 
Rheumatoid arthritis:
ROM, pain, joint swelling before, during treatment

• 
Psoriasis:
skin lesions before, during treatment

Perform/provide:

• 
Increased fluid intake to 2-3 L/day to prevent urate deposits, calculi formation unless contraindicated

• 
Rinsing of mouth tid-qid with water, club soda; brushing of teeth bid-tid with soft brush or cotton-tipped applicators for stomatitis; use unwaxed dental floss

• 
Storage in tightly closed container in cool environment; store injection, powder for inj in dark, dry area

Evaluate:

• 
Therapeutic response: decreased tumor size, spread of malignancy; decreased joint inflammation, pain in RA

Teach patient/family:

 

Black Box Warning:

To report any complaints, side effects to nurse or prescriber: black tarry stools, chills, fever, sore throat, bleeding, bruising, cough, SOB, dark or bloody urine, seizures

• 
That hair may be lost during treatment; that wig or hairpiece may make patient feel better; that new hair may be different in color, texture (alopecia rare)

• 
To avoid foods with citric acid, hot or rough texture if stomatitis is present

• 
To report stomatitis and any bleeding, white spots, ulcerations in mouth to prescriber; to examine mouth daily; to report symptoms to nurse; to use good oral hygiene

 

Black Box Warning:

That contraceptive measures are recommended during therapy and for at least 8 wk after cessation of therapy for women and men; to discontinue breastfeeding; that toxicity to infant may occur; pregnancy (X)

• 
To drink 10-12 glasses of fluid/day

• 
To avoid alcohol, salicylates, live vaccines

• 
To avoid use of razors, commercial mouthwash

• 
To use sunblock to prevent burns

• 
To use good dental care, to prevent overgrowth of infection in the mouth

• 
How to use this product with leucovorin rescue

• 
To continue leucovorin until told it is safe to stop

• 
To report CNS symptoms, vision changes

• 
To report fever, other symptoms of infection

• 
To report decreased urine output

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