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INTRODUCTION

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HIGH ALERT

mercaptopurine (mer-kap-toe-pyoor-een)

Purinethol

Classification

Therapeutic: antineoplastics

Pharmacologic: antimetabolites

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Indications
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Leukemias (with other agents), including Acute lymphocytic leukemia, Acute myelogenous leukemia. Unlabeled Use: Treatment of Some lymphomas, Polycythemia vera, Crohn's disease, Psoriatic arthritis.

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Action
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Disrupts DNA and RNA synthesis (cell-cycle S phase–specific). Therapeutic Effects: Death of rapidly proliferating cells, especially malignant ones. Also has immunosuppressant properties.

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Adverse Reactions/Side Effects
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CNS: weakness. GI: HEPATOTOXICITY, anorexia, diarrhea, nausea, vomiting. Derm: alopecia, hyperpigmentation. Endo: gonadal suppression, oligospermia. Hemat: anemia, leukopenia, thrombocytopenia. Metab: hyperuricemia. Misc: fever.

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PHYSICAL THERAPY IMPLICATIONS

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Examination and Evaluation
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  • Be alert for signs of hepatotoxicity, including anorexia, abdominal pain, severe nausea and vomiting, yellow skin or eyes, fever, sore throat, malaise, weakness, facial edema, lethargy, and unusual bleeding or bruising. Report these signs to the physician or nursing staff immediately.

  • Instruct patient to report signs of leukopenia (fever, sore throat, signs of infection), thrombocytopenia (bruising, nose bleeds, bleeding gums), or unusual weakness and fatigue that might be due to anemia. Report these signs to the physician or nursing staff.

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Interventions
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  • For patients who are medically able to begin exercise, implement appropriate resistive exercises and aerobic training to maintain muscle strength and aerobic capacity during cancer chemotherapy or to help restore function after chemotherapy.

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Patient/Client-Related Instruction
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  • Because of immunosuppressant effects, advise patient to decrease risk of infections (frequent hand washing, etc.) and avoid contact with persons with contagious diseases.

  • Advise patient and family/caregivers that fatigue and weakness are likely and may be severe. Functional abilities may be limited, and patient may need to use assistive devices during ambulation.

  • Advise patient that hair loss, changes in skin color, and other skin reactions are likely. Report severe or unexpected skin reactions to the physician.

  • Instruct patient to report other troublesome side effects such as severe or prolonged fever or GI problems (nausea, vomiting, diarrhea, loss of appetite).

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Pharmacokinetics
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Absorption: Variably and incompletely (5–50%) absorbed after oral administration.

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Distribution: Widely distributed throughout total body water.

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Metabolism and Excretion: Metabolized by liver. Some metabolism by the GI mucosa. Nearly 50% is excreted unchanged by the kidneys.

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Half-life: Three phases—45 min, 2.5 hr, 10 hr.

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TIME/ACTION PROFILE (effects on blood counts)

ROUTE ONSET PEAK DURATION
PO 7–10 days 14 days 21 days

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Contraindications/Precautions
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Contraindicated in: Hypersensitivity; Pregnancy or lactation; Severe liver disease.

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Use Cautiously in: Infections; ↓ bone marrow reserve;

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Geri: ↑ risk of adverse reactions; Other chronic debilitating illnesses; OB: Patients ...

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