Penicillin VK

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Description
Clinical Pharmacology
Indications and Usage
Contraindications
Warnings
Precautions
Adverse Reactions
Overdosage
Dosage and Administration
References

Description:

Penicillin V potassium, USP is the potassium salt of penicillin V, USP. This chemically improved form combines acid stability with immediate solubility and rapid absorption. It is designated 4-thia-1-azabicyclo[3.2.0]-heptane-2-carboxylic acid, 3,3 -dimethyl-7-oxo-6-[(phenoxyacetyl)amino]-, monopotassium salt, [2S-(2alpha,5alpha,6beta)]-. The empirical formula is C₁₆H₁₇KN₂O₅S, and the molecular weight is 388.48.

Each tablet contains penicillin V potassium equivalent to 250 mg (400,000 units) or 500 mg (800,000 units) penicillin V. The tablets also contain lactose, magnesium stearate, povidone, starch, stearic acid, and other inactive ingredients.

After being mixed as directed, each 5 ml of the oral solution will contain penicillin V potassium equivalent to 250 mg (400,000 units) penicillin V. The suspension also contains citric acid, F D & C Red No. 40, flavors, saccharin, sodium citrate, and sucrose.

The potassium content of the tablets and oral solution is listed below (TABLE 1).

TABLE 1 -

Clinical Pharmacology:

Penicillin V potassium is bactericidal against penicillin-susceptible microorganisms during the stage of active multiplication. It produces its effect by inhibiting biosynthesis of cell-wall mucopeptide. It is not active against the penicillinase-producing bacteria, which include many strains of staphylococci. The drug exerts high in vitro activity against staphylococci (except penicillinase-producing strains), streptococci (groups A, C, G, H, L, and M), and pneumococci. Other organisms susceptible in vitro to penicillin V areCorynebacterium diphtheriae, Bacillus anthracis, clostridia,Actinomyces bovis, Streptobacillus moniliformis, Listeria monocytogenes, Leptospira, and Neisseria gonorrhoeae.Treponema pallidium is extremely susceptible.

Penicillin V potassium has the distinct advantage over penicillin G in being resistant to inactivation by gastric acid. It may be given with meals; however, blood levels are slightly higher when the drug is given on an empty stomach. Average blood levels are 2 to 5 times higher than those following the same dose of oral penicillin G and also show much less individual variation.

Once absorbed, about 80% of penicillin V potassium is bound to serum protein. Tissue levels are highest in the kidneys, and lesser amounts appear in the liver, skin, and intestines. Small concentrations are found in all other body tissues and the cerebrospinal fluid. The drug is excreted as rapidly as it is absorbed in individuals with normal kidney function; however, recovery of the drug from the urine indicates that only about 25% of the dose given is absorbed. In neonates, young infants, and individuals with impaired kidney function, excretion is considerably delayed.

Indications and Usage:

Penicillin V potassium is indicated in the treatment of mild to moderately severe infections due to microorganisms whose susceptibility to penicillin G is within the range of serum levels common to this particular dosage form. Therapy should be guided by bacteriologic studies (including susceptibility tests) and by clinical response.

NOTE: Severe pneumonia, empyema, bacteremia, pericarditis, meningitis, and arthritis should not be treated with penicillin V during the acute stage.

Indicated surgical procedures should be performed.

The following infections will usually respond to adequate dosage of penicillin V:

Streptococcal Infections (without bacteremia): Mild to moderate infections of the upper respiratory tract, scarlet fever, and mild erysipelas.

NOTE: Streptococci groups A, C, G, H, L, and M are very susceptible to penicillin. Other groups, including group D (enterococcus), are resistant.

Pneumococcal Infections: Mild to moderately severe infections of the respiratory tract.

Staphylococcal Infections Susceptible to Penicillin G: Mild infections of the skin and soft tissues.

NOTE: Reports indicate an increasing number of strains of staphylococci resistant to penicillin G, which emphasizes the need for culture and susceptibility studies in treating suspected staphylococcal infections.

Fusospirochetosis (Vincent's Gingivitis and Pharyngitis): Mild to moderately severe infections of the oropharynx usually respond to therapy with oral penicillin.

NOTE: Necessary dental care should be accomplished in infections involving the gum tissue.

Medical Conditions in Which Oral Penicillin Therapy Is Indicated as Prophylaxis: To prevent recurrence following rheumatic fever and/or chorea. Prophylaxis with oral penicillin on a continuing basis has proved effective in preventing recurrence of these conditions.

Although no controlled clinical efficacy studies have been conducted, penicillin V has been suggested by the American Heart Association and the American Dental Association for use as an oral regimen for prophylaxis against bacterial endocarditis in patients with congenital heart disease or rheumatic or other acquired valvular heart disease when they undergo dental procedures and surgical procedures of the respiratory tract.¹

Since alpha-hemolytic streptococci relatively resistant to penicillin may be found when patients are receiving continuous oral penicillin for secondary prevention of rheumatic fever, prophylactic agents other than penicillin may be chosen for these patients and prescribed in addition to their continuous prophylactic regimen for rheumatic fever.

Oral penicillin should not be used as adjunctive prophylaxis for genitourinary instrumentation or surgery, lower intestinal tract surgery, sigmoidoscopy, and childbirth.

NOTE: When selecting antibiotics for the prevention of bacterial endocarditis, the physician or dentist should read the full joint statement of the American Heart Association and the American Dental Association.¹

Contraindications:

A previous hypersensitivity reaction to any penicillin is a contraindication.

Warnings:

SERIOUS AND OCCASIONALLY FATAL HYPERSENSITIVITY (ANAPHYLACTIC) REACTIONS HAVE BEEN REPORTED IN PATIENTS RECEIVING PENICILLIN THERAPY. THESE REACTIONS ARE MORE LIKELY TO OCCUR IN INDIVIDUALS WITH A HISTORY OF PENICILLIN HYPERSENSITIVITY AND/OR A HISTORY OF SENSITIVITY TO MULTIPLE ALLERGENS. THERE HAVE BEEN REPORTS OF INDIVIDUALS WITH A HISTORY OF PENICILLIN HYPERSENSITIVITY WHO HAVE EXPERIENCED SEVERE REACTIONS WHEN TREATED WITH CEPHALOSPORINS. BEFORE INITIATING THERAPY WITH PENICILLIN V POTASSIUM, CAREFUL INQUIRY SHOULD BE MADE CONCERNING PREVIOUS HYPERSENSITIVITY REACTIONS TO PENICILLINS, CEPHALOSPORINS, OR OTHER ALLERGENS. IF AN ALLERGIC REACTION OCCURS, PENICILLIN V POTASSIUM SHOULD BE DISCONTINUED AND APPROPRIATE THERAPY INSTITUTED. SERIOUS ANAPHYLACTIC REACTIONS REQUIRE IMMEDIATE EMERGENCY TREATMENT WITH EPINEPHRINE. OXYGEN, INTRAVENOUS STEROIDS, AND AIRWAY MANAGEMENT, INCLUDING INTUBATION, SHOULD ALSO BE ADMINISTRATED AS INDICATED.

Pseudomembranous colitis has been reported with nearly all antibacterial agents including penicillins, and may range in severity from mild to life-threatening. Therefore, it is important to consider this diagnosis in patients who present with diarrhea subsequent to the administration of antibacterial agents.

Treatment with antibacterial agents alters the normal flora of the colon and may permit overgrowth of clostridia. Studies indicate that a toxin produced by Clostridium difficile is one primary cause of "antibiotic-associated colitis."

After the diagnosis of pseudomembranous colitis has been established, therapeutic measures should be initiated. Mild cases of pseudomembranous colitis usually respond to drug discontinuation alone. In moderate to severe cases, consideration should be given to management with fluids and electrolytes, protein supplementation, and treatment with an antibacterial drug clinically effective against C. difficile colitis.

Precautions:

Penicillin should be used with caution in individuals with histories of significant allergies and/or asthma.

The oral route of administration should not be relied upon in patients with severe illness or with nausea, vomiting, gastric dilatation, cardiospasm, or intestinal hypermotility.

Occasional patients will not absorb therapeutic amounts of orally administered penicillin.

In streptococcal infections, therapy must be sufficient to eliminate the organism (a minimum of 10 days); otherwise, the sequelae of streptococcal disease may occur. Cultures should be taken following completion of treatment to determine whether streptococci have been eradicated.

Prolonged use of antibiotics may promote the overgrowth of nonsusceptible organisms, including fungi. If superinfection occurs, appropriate measures should be taken.

Adverse Reactions:

Although reactions have been reported much less frequently after oral than after parenteral penicillin therapy, it should be remembered that all degrees of hypersensitivity, including fatal anaphylaxis, have been observed with oral penicillin.

The most common reactions to oral penicillin are nausea, vomiting, epigastric distress, diarrhea, and black, hairy tongue. The hypersensitivity reactions noted are skin eruptions (ranging from maculopapular to exfoliative dermatitis); urticaria; reactions resembling serum sickness, including chills, fever, edema, arthralgia, and prostration; laryngeal edema; and anaphylaxis. Fever and eosinophilia may frequently be the only reactions observed. Hemolytic anemia, leukopenia, thrombocytopenia, neuropathy, and nephropathy are infrequent reactions and are usually associated with high doses of parenteral penicillin.

Overdosage:

Signs and Symptoms: Symptoms of large oral overdose of penicillin may cause nausea, vomiting, stomach pain, diarrhea, and, in rare cases, major motor seizures. If other symptoms are present, consideration must also be given to the possibility of an allergic reaction or symptoms secondary to a concurrent medication or other underlying disease state, especially in adults.

Treatment: To obtain up-to-date information about the treatment of overdose, a good resource is your certified Regional Poison Control Center. Telephone numbers of certified poison control centers are listed in Physicians GenR_x. In managing overdosage, consider the possibility of multiple drug overdoses, interaction among drugs, and unusual drug kinetics in your patient.

Ensure adequate ventilation and protect the patient's airway while attempting to limit drug absorption. In oral overdosage, consideration must be given to emesis or lavage to evacuate the stomach, and administration of activated charcoal by mouth or via lavage tube with a cathartic such as sorbitol may hasten drug elimination. Penicillin may be removed by hemodialysis. No specific antidote is known to be effective.

Dosage and Administration:

The dosage of penicillin V potassium should be determined according to the susceptibility of the causative microorganism and the severity of infection and should be adjusted to the clinical response of the patient.

The usual dosage recommendations for adults and children 12 years and over are as follows:

Streptococcal Infections: Mild to moderately severe infections of the upper respiratory tract, including scarlet fever and mild erysipelas: 200,000 to 500,000 units every 6 to 8 hours for 10 days.

Pneumococcal Infections: Mild to moderately severe infections of the respiratory tract, including otitis media: 400,000 to 500,000 units every 6 hours until the patient has been afebrile for at least 2 days.

Staphylococcal Infections: Mild infections of skin and soft tissue (culture and susceptibility tests should be performed): 400,000 to 500,000 units every 6 to 8 hours.

Fusospirochetosis (Vincent's Infection) of the Oropharynx: Mild to moderately severe infections: 400,000 to 500,000 units every 6 to 8 hours.

Prophylaxis in the Following Conditions: To prevent recurrence following rheumatic fever and/or chorea: 200,000 to 250,000 units twice daily on a continuing basis.

For prophylaxis against bacterial endocarditis¹in patients with congenital heart disease or rheumatic or other acquired valvular heart disease when undergoing dental procedures or surgical procedures of the upper respiratory tract, 1 of 2 regimens may be selected:

For the oral regimen, the usual adult dosage is 2 g of penicillin V (1 g for children less than 30 kg) 1 hour before the procedure and then 1 g (500 mg for children less than 30 kg) 6 hours later.

For patients unable to take oral antibiotics, 2,000,000 units of aqueous penicillin G (50,000 units/kg for children) IV or IM may be substituted 30 to 60 minutes before the procedure and 1,000,000 units (25,000 units/kg for children) 6 hours later.

For patients with prosthetic valves and for those at highest risk for endocarditis, ampicillin, 1 to 2 g (50 mg/kg for children), plus gentamicin, 1.5 mg/kg (2 mg/kg for children), IM or IV, may be given one- half hour prior to the procedure, followed by 1 g of oral penicillin V 6 hours later. Alternatively, the parenteral regimen should be repeated once every 8 hours later.

Children's antibiotic dosages should not exceed the maximum adult doses.

NOTE: Therapy for children under 12 years of age is calculated on the basis of body weight. For infants and small children, the suggested daily dose is 25,000 to 90,000 units (15 to 50 mg)/kg in 3 to 6 divided doses.

After being mixed, the solution should be stored in a refrigerator. It may be kept for 14 days without significant loss of potency. Shake well before using. Keep tightly closed.

Tablets should be stored at controlled room temperature, 59° to 86°F (15° to 30°C).

References:

1. Dajani AS, Bisno AL, et al: Prevention of bacterial endocarditis. Recommendations by the American Heart Association.JAMA, 1990;264:2919.

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