penicillin V potassium

Apo-Pen VK (CA), Novo-Pen-VK (CA), Pen-Vee

Pharmacologic class: Penicillin

Therapeutic class: Anti-infective

Pregnancy risk category B

Action

Inhibits biosynthesis of cell-wall mucopeptide; bactericidal against penicillin-susceptible microorganisms during active multiplication stage

Availability

Oral solution: 200,000 units (125 mg)/5 ml, 400,000 units (250 mg)/5 ml

Tablets: 400,000 units (250 mg), 800,000 units (500 mg)

Indications and dosages

➣ Upper respiratory streptococcal infections, including scarlet fever and mild erysipelas

Adults and children ages 12 and older: 125 to 250 mg P.O. q 6 to 8 hours for 10 days

Children younger than age 12: 25 to 50 mg/kg/day P.O. in divided doses q 6 hours for 10 days

➣ Pneumococcal respiratory infections, including otitis media

Adults and children ages 12 and older: 250 to 500 mg P.O. q 6 hours until afebrile for at least 2 days

➣ Skin and soft-tissue staphylococcal infections; fusospirochetosis (Vincent's infection) of oropharynx

Adults and children ages 12 and older: 250 to 500 mg P.O. q 6 to 8 hours

➣ To prevent recurrence of rheumatic fever or chorea

Adults and children ages 12 and older: 125 to 250 mg P.O. b.i.d. on a continuing basis

Off-label uses

• Prophylaxis of Streptococcus pneumoniae septicemia in children with sickle cell anemia or splenectomy

• Early Lyme disease

• Actinomycosis

• Preexposure prophylaxis of anthrax

• Prophylaxis of bacterial endocarditis for dental procedures

Contraindications

• Hypersensitivity to penicillins or beta-lactamase inhibitors (piperacillin/tazobactam)

Precautions

Use cautiously in:

• severe renal insufficiency

• pregnant or breastfeeding patients.

Administration

• Before giving, ask patient about allergies to penicillin, beta-lactamase inhibitors, or benzathine. Know that cross-sensitivity to imipenem and cephalosporins may occur.

See Keep epinephrine and emergency equipment at hand in case anaphylaxis occurs.

• Give with water 1 hour before or 2 hours after meals. Don't give with fruit juice or carbonated beverages.

Adverse reactions

CNS: lethargy, hallucinations, anxiety, depression, twitching, seizures, coma

GI: nausea, vomiting, diarrhea, epigastric distress, abdominal pain, colitis, blood in stool, glossitis, pseudomembranous colitis

GU: interstitial nephritis

Hematologic: anemia, hemolytic anemia, increased bleeding, leukopenia, granulocytopenia, bone marrow depression, thrombocytopenia, thrombocytopenic purpura

Metabolic: hypokalemia, hyperkalemia, metabolic alkalosis

Skin: rash, urticaria

Other: fever, superinfection, anaphylaxis, serum sickness

Interactions

Drug-drug. Aspirin, probenecid: increased penicillin blood level

Erythromycins, tetracyclines: decreased antimicrobial activity of penicillin

Hormonal contraceptives: decreased contraceptive efficacy

Drug-diagnostic tests. Alanine aminotransferase, eosinophils, granulocytes, hemoglobin, platelets: increased levels Albumin, lymphocytes, protein, sodium, uric acid, white blood cells: decreased levels

Direct Coombs' test: positive result

Potassium: increased or decreased level

Urine glucose, urine protein: false-positive results

Drug-herbs. Khat: delayed and reduced penicillin absorption

Patient monitoring

See Watch for signs and symptoms of anaphylaxis and serum sickness.

• In long-term therapy, monitor electrolyte levels and CBC with white cell differential; watch for electrolyte imbalances and blood dyscrasias.

• Assess neurologic status, especially for seizures and decreasing level of consciousness.

See Monitor patient closely for signs and symptoms of superinfection and pseudomembranous colitis.

Patient teaching

• Instruct patient to take with water 1 hour before or 2 hours after meals. Tell him not to take with fruit juice or carbonated beverages.

See Teach patient to recognize anaphylaxis symptoms. Tell him to immediately contact emergency medical services if these occur.

• Instruct patient to report signs and symptoms of superinfection.

• Advise patient to contact prescriber if infection symptoms get worse.

See Tell patient drug may cause diarrhea. Instruct him to immediately report severe, persistent diarrhea and fever.

• Instruct patient to complete entire course of therapy as prescribed, even after symptoms improve.

• Tell female patient drug may make hormonal contraceptives ineffective. Advise her to use barrier birth-control method if she wishes to avoid pregnancy.

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