Allopurinol is most commonly sold under the brand names Aloprim and Zyloprim. As nurses, be sure not to confuse allopurinol with haloperidol or Apresoline, Zyloprim with Zorprin, or Zyloric with Zovirax.
Allopurinol works by decreasing uric acid production by inhibiting xanthine oxidase- an enzyme responsible for converting xanthine to uric acid, hence exerting the therapeutic effects of reducing uric acid concentrations in serum and urine.
When given orally or through an intravenous (IV) route, the onset of action occurs in 2 to 3 days, achieves peak in 1 week, and the duration of action is 1 to 2 weeks.
When given orally, allopurinol is well absorbed from the gastrointestinal tract, widely distributed in the body, and has a protein binding of less than 1%. Moreover, it is metabolized in the liver, excreted primarily in urine, and can be removed through hemodialysis. Its half-life is 1 to 3 hours, and the metabolite has a life of 12 to 30 hours.
Precautions and Contraindications
Allopurinol use is contraindicated in patients with hypersensitivity to it. It should be given with caution in patients with renal and hepatic impairment, those taking diuretics or other drugs, such as mercaptopurine or azathioprine, or those taking drugs that cause myelosuppression. Moreover, it should not be used in asymptomatic hyperuricemia.
Drug Interactions
Various drug interactions can occur when allopurinol is combined with other drugs. When given with angiotensin-converting enzyme (ACE) inhibitors such as lisinopril, enalapril, and captopril, the risk of allergy and hypersensitivity reactions is increased. Antacids may decrease the absorption of allopurinol. Moreover, it can increase the concentration of azathioprine, mercaptopurine, and didanosine, leading to increased effects and side effects of these drugs.
Allopurinol can also increase the adverse effects of pegloticase and the anticoagulant effects of vitamin K antagonists, such as warfarin. Moreover, it may decrease the effects and concentration of capecitabine.
Allopurinol may also alter lab values, increasing serum blood urea nitrogen (BUN), alanine transaminase (ALT), aspartate aminotransferase (AST), alkaline phosphatase, and creatinine. Therefore, keep an eye on liver and kidney function tests with allopurinol therapy.
Availability, Administration, and Handling
Allopurinol is available as a tablet dosage form in 100 milligrams (mg) and 300 mg strengths. It is also available as an injection powder for reconstitution as a 500 mg vial. To reconstitute the vial, use water for injection and mix 500 mg to the strength of 20 mg/milliliter (ml). Further, it can be diluted with 0.9% sodium chloride (NaCl) or dextrose water using 50 to 100 ml to a concentration of 6 mg/ml or less. Infuse slowly over 15 to 60 minutes. To administer daily doses, it can be given as a single infusion or in equally divided doses at intervals of 6, 8, or 12 hours. The prepared solution should appear clear and colorless.
You can store the reconstituted vials at room temperature. However, do not refrigerate the reconstituted or diluted solutions. After reconstitution, the infusion should be administered within 10 hours of preparation. Make sure to discard the preparation if precipitates are formed or the solution appears discolored.
For oral administration, give the allopurinol tablet after meals with plenty of fluid. With adequate fluid intake, the patient should yield slightly alkaline urine with an output of 2 liters (L). Moreover, dosages greater than 300 mg/day should be administered in divided doses.
Allopurinol is incompatible with the following drugs for concomitant IV administration:
- Amikacin (Amikin)
- Carmustine (BiCNU)
- Cefotaxime (Claforan)
- Clindamycin (Cleocin)
- Cytarabine (Ara-C),
- Dacarbazine (DTIC)
- Diphenhydramine (Benadryl),
- Doxorubicin (Adriamycin)
- Doxycycline (Vibramycin)
- Gentamicin
- Haloperidol (Haldol)
- Hydroxyzine (Vistaril)
- Idarubicin (Idamycin)
- Imipenem-cilastatin (Primaxin)
- Methylprednisolone (Solumedrol)
- Metoclopramide (Reglan)
- Ondansetron (Zofran)
- Streptozocin (Zanosar)
- Tobramycin
- Vinorelbine (Navelbine)
Allopurinol is compatible with the following drugs when concomitantly administered intravenously.
- Bumetanide (Bumex)
- Calcium gluconate
- Heparin
- Hydromorphone (Dilaudid)
- Lorazepam (Ativan)
- Morphine
- Potassium chloride
- Dosage of Allopurinol
For the treatment of gout, allopurinol is often given orally to adults and the elderly to treat gout. The initial dose is 100 mg a day. If needed, the dose is increased at weekly intervals to achieve the desired serum uric acid level. For mild gout, 200 to 300 mg per day is given, while for moderate to severe cases, 400 to 600 mg per day is given in 2 to 3 divided doses. The maximum dose of allopurinol is 800 mg per day.
For the treatment of secondary hyperuricemia associated with chemotherapy, the dose of allopurinol is:
- Given orally to adults and children older than 10 years, 600 to 800 mg per day, given in 2 to 3 divided doses starting one to two days before chemotherapy.
- In children aged 6 to 10 years, the dose is 300 mg daily in 2 to 3 divided doses. For children younger than 6 years, the dose is 150 mg in a day given in 3 divided doses.
- The IV dose of allopurinol for adults and children 10 years or older is 200 to 400 mg/m2/day beginning 24 to 48 hours before the initiation of chemotherapy. For children younger than 10 years, the dose is 200 mg/m2/day, beginning 24 to 48 hours before starting the chemotherapy. The maximum dose of allopurinol for children younger than 10 years is 600 mg/day.
For recurrent uric acid calcium oxalate calculi, the dose of allopurinol in adults is given orally 200 to 300 mg per day in single or divided doses.
In patients with renal impairment, the dose of allopurinol is given, considering the creatinine clearance. So, dose adjustment is required in patients with impaired kidney function.
- When creatinine clearance is 10 to 20 ml/min, the dose of allopurinol is 200 mg per day.
- When creatinine clearance is 3 to 9 ml/min, the dose of allopurinol is 100 mg per day.
- When creatinine clearance is less than 3 ml/min, the allopurinol dose is 100 mg and given in extended intervals.
- For patients dependent on hemodialysis, the dose of allopurinol is 100mg given every 48 hours. It should be increased very cautiously to 300 mg every 48 hours if required.
Side Effects and Adverse Effects
Allopurinol is generally well tolerated. However, it can cause occasional side effects, including unusual hair loss and drowsiness. Following IV administration, allopurinol can cause a rash, nausea, or vomiting.
When given in higher than recommended doses, allopurinol can cause adverse effects, such as pruritic maculopapular rash, malaise, fever, chills, nausea, vomiting, and joint pain, indicating a severe toxic reaction. Rarely, it may cause hepatotoxicity, bone marrow depression, peripheral neuritis, and acute renal failure.
Nursing Considerations
When administering allopurinol, obtain baseline tests of the patient before starting the therapy. Check the liver function tests and basic metabolic panel, which includes measuring serum calcium, carbon dioxide, chloride, creatinine, glucose, potassium, sodium, and BUN. If any of these levels are altered, discuss them with the primary healthcare provider before starting the therapy.
When starting allopurinol therapy, advise the patient to take the medication with plenty of fluids. They should drink at least 2,500 to 3,000 ml (2.5 to 3 liters) of fluids daily when taking the medication. Additionally, instruct them to take it with food, not on an empty stomach.
If the patient complains about allergic reaction symptoms, such as difficulty breathing, cough, increased mucus secretion, dizziness, rashes, and hives, stop the drug immediately and treat the condition accordingly.
With allopurinol therapy, urine input and output are monitored. The output should be at least 2000 ml per day. Inform the patient that the drug will cause increased urination; this might hinder their daily routine activities. Moreover, their serum chemistries, including uric acid and hepatic function, should be assessed. Check the urine for cloudiness and unusual color or odor. Educate the patient to keep taking the drug even if their gout attack has subsided. They should not stop their intake without guidance from their primary provider.
Assess the patient for the therapeutic response of allopurinol. Check for pain relief, swelling, stiffness, reduced joint tenderness, and improved grip strength. Allopurinol can precipitate a gout attack even when the uric acid levels are normal. Therefore, co-administration of colchicine or an antiinflammatory drug may help prevent the worsening of a gout attack. Moreover, the dose of allopurinol should be increased gradually.
Patient and Family Teaching
With allopurinol therapy, it is essential to educate the patient and their caregivers. Tell them the drug may take one week or longer to show its therapeutic effects. Educate them to drink plenty of water and make sure to consume 2,500 to 3,000 ml of fluid with the medication intake. Inform them to avoid doing tasks that require alertness and motor skills until the response to the drug is established, as it can cause drowsiness and impair judgment. Also, counsel them to avoid alcohol consumption as it can increase serum uric acid levels.
Inform the patient that starting allopurinol can sometimes flare the gout attack, but they should keep taking the medication, and it will settle down on its own.
The Bottom Line
Allopurinol is used to treat gout and hyperuricemia associated with cancer chemotherapy. It is important for the patient to take the medication on time and as directed, with plenty of water after food intake. Patients should be educated not to stop taking the medication abruptly, even when the acute gout attack has subsided. It's important to encourage patients to attend follow-up visits as well.
About the Author:
Mariya Rizwan is an experienced pharmacist who has been working as a medical writer for four years. Her passion lies in crafting articles on topics ranging from Pharmacology, General Medicine, Pathology to Pharmacognosy.
Mariya is an independent contributor to CEUfast's Nursing Blog Program. Please note that the views, thoughts, and opinions expressed in this blog post are solely of the independent contributor and do not necessarily represent those of CEUfast. This blog post is not medical advice. Always consult with your personal healthcare provider for any health-related questions or concerns.
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