Macrobid

Action

Inhibits bacterial enzymes required for normal cell activity at low concentrations; inhibits normal cell-wall synthesis at high concentrations

Availability

Capsules: 25 mg, 50 mg, 100 mg (macrocrystals)

Capsules (extended-release): 100 mg (macrocrystals)

Oral suspension: 25 mg/5 ml

Tablets: 50 mg, 100 mg (macrocrystals)

Indications and dosages

➣ Active urinary tract infections (UTIs)

Adults: 50 to 100 mg P.O. q.i.d. or 100 mg q 12 hours (extended-release), continued for 1 week, or for 3 days after urine becomes sterile

Children older than 1 month: 5 to 7 mg/kg/day P.O. in four divided doses, continued for 1 week, or for 3 days after urine becomes sterile

➣ Chronic suppression of UTIs

Adults: 50 to 100 mg P.O. at bedtime

Children: 1 mg/kg/day P.O. in one or two divided doses

Contraindications

• Hypersensitivity to drug or parabens (oral suspension)

• Oliguria, anuria, or significant renal impairment

• Pregnancy near term (38 to 42 weeks' gestation), imminent labor onset, labor and delivery

• Infants younger than 1 month

Precautions

Use cautiously in:

• diabetes mellitus, renal impairment

• blacks and patients of Mediterranean or near-Eastern descent (because of possible G6PD deficiency)

• elderly or debilitated patients

• pregnant (to week 32) or breastfeeding patients.

Administration

• As appropriate, obtain specimens for repeat urine culture and sensitivity tests before therapy.

• To avoid GI upset and increase drug bioavailability, give with food or milk.

Adverse reactions

CNS: dizziness, drowsiness, headache, asthenia, peripheral neuropathy, vertigo

CV: chest pain

EENT: nystagmus

GI: nausea, vomiting, diarrhea, abdominal pain, anorexia, parotitis, pancreatitis

Hematologic: eosinophilia, agranulocytosis, thrombocytopenia, leukopenia, granulocytopenia, G6PD deficiency anemia, hemolytic anemia, megaloblastic anemia

Hepatic: hepatitis, hepatic necrosis

Musculoskeletal: arthralgia, myalgia

Respiratory: asthma attacks, pulmonary hypersensitivity reactions including diffuse interstitial pneumonias (with prolonged therapy)

Skin: rash, exfoliative dermatitis, alopecia, pruritus, urticaria, angioedema, photosensitivity, Stevens-Johnson syndrome

Other: drug fever, chills, superinfection (limited to urinary tract), hypersensitivity reactions including anaphylaxis, lupus-like syndrome

Interactions

Drug-drug. Anticholinergics: increased nitrofurantoin absorption and bioavailability

Drugs that can cause pulmonary toxicity: increased risk of pneumonitis

Hepatotoxic drugs: increased risk of hepatotoxicity

Magnesium salts: decreased nitrofurantoin absorption

Neurotoxic drugs: increased risk of neu-rotoxicity

Uricosurics (such as probenecid): decreased renal clearance and increased blood level of nitrofurantoin

Drug-diagnostic tests. Alanine aminotransferase, alkaline phosphatase, aspartate aminotransferase, bilirubin, blood urea nitrogen, creatinine: increased levels Granulocytes, platelets, hemoglobin: decreased levels

Urine glucose tests using Benedict's reagent or Fehling's solution: false-positive results

Drug-food. Any food: increased drug bioavailability

Patient monitoring

• Monitor patient's response to therapy. Assess urine culture and sensitivity tests.

Watch for and immediately report peripheral neuropathy.

Assess respiratory status. Watch for signs and symptoms of serious pulmonary hypersensitivity reaction.

Monitor CBC and liver function tests closely. Stay alert for evidence of hematologic and hepatic disorders.

• Evaluate patient for rash.

Patient teaching

• Instruct patient to take with food or milk at regular intervals around the clock.

• Advise patient to complete entire course of therapy.

• Tell patient not to take magnesium-containing drugs (such as antacids) during therapy.

• Caution patient not to drive or perform other hazardous activities until he knows how drug affects vision, concentration, and alertness.

Tell patient to immediately report fever, chills, cough, chest pain, difficulty breathing, rash, bleeding or easy bruising, dark urine, yellowing of skin or eyes, numbness or tingling of fingers or toes, or intolerable GI distress.

• Advise female patient to avoid taking drug during pregnancy, especially near term.

• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, tests, and foods mentioned above.