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Penicillin V potassium (Phenoxymethylpenicillin) is the potassium salt of penicillin V. This chemically improved form combines acid stability with immediate solubility and rapid absorption.

Penicillin V potassium exerts high in vitro activity against staphylococci (except penicillinase-producing strains), streptococci (groups A, C, G, H, L and M), and pneumococci.

The discovery of penicillin has often been described as a miracle drug, and that is exactly what it was.

Originally it was noticed by a French medical student, Ernest Duchesne, in 1896. Penicillin was re-discovered by bacteriologist Alexander Fleming working at St. Mary's Hospital in London in 1928. He observed that a plate culture of Staphylococcus had been contaminated by a blue-green mold and that colonies of bacteria adjacent to the mold were being dissolved. Curious, Alexander Fleming grew the mold in a pure culture and found that it produced a substance that killed a number of disease-causing bacteria. Naming the substance penicillin, Dr. Fleming in 1929 published the results of his investigations, noting that his discovery might have therapeutic value if it could be produced in quantity.

• Streptococcal infections (without bacteremia) - mild to moderate infections of the upper respiratory tract, scarlet fever, and mild erysipelas.
• Pneumococcal infections - mild to moderately severe infections of the respiratory tract.
• Staphylococcal infections (penicillin G-sensitive) - mild infections of the skin and soft tissues.
• Fusospirochetosis (Vincent's gingivitis and pharyngitis) - mild to moderately severe infections of the oropharynx usually respond to therapy with oral penicillin.
• Prevention of recurrence following rheumatic fever and/or chorea: Prophylaxis with oral penicillin on a continuing basis has proven effective in preventing recurrence of these conditions.

Only mild to moderate infections are treated with oral penicillin. Patients with more severe infections can be given penicillin by injection.

• Prophylactic treatment of sickle cell anemia in children4
• Anaerobic infections5-6
• Lyme disease (erythema migrans)7
  Lyme disease is caused when an Ixodes tick passes on the germ known as "Borrelia burgdorferi," while sucking blood from its victim. Most people who get Lyme disease will show a rounded red rash at the place the tick bit them within a month. Some never develop a rash, while others develop multiple spots. The rash is called erythema migrans (formerly erythema chronicum migrans).
• Endocarditis8-9

Advantages:

• May be taken with meals - resistant to inactivation by gastric acid.
• Bactericidal against sensitive bacteria.
• Relatively non-toxic
• Excellent tissue penetration
• Low cost. Relatively inexpensive in comparison with other antibiotics.
• Pregnancy category B. Penicillin is considered safe during pregnancy.
• Less likely to induce antimicrobial resistance than broad spectrum antibiotics.

Disadvantages:

• Frequent dosage regimen. Because of its short half-life, penicillin must be administered at short intervals, usually every 6 hours.
• Drug hypersensivity (penicillin allergy) - about 10% of population has allergy. All degrees of hypersensitivity, including fatal anaphylaxis, have been reported with penicillin.
• Unpalatable suspension. Children don't like the taste of penicillin2.
• Narrow antibacterial spectrum.

Penicillin VK exerts a bactericidal action and acts during the period of bacterial multiplication, inhibiting the biosynthesis of the mucopeptide of the cell wall.

Penicillin VK half-life is 0.5 to 1 hr. So it takes about 5 hr to clear out of the system.

Streptococcal sore throat is an infection with the group A beta-haemolytic streptococcus (Streptococcus pyogenes). Although this condition will usually resolve without treatment, the infection may be complicated by otitis media, and rarely by peritonsillar abscess (quinsy), or rheumatic fever.

Penicillin is normally the antibiotic of choice for streptococcal pharyngitis. Group A streptococci remain fully sensitive to penicillin.

A twice daily regimen is probably as effective as four times daily and may improve compliance. Unfortunately, many children dislike the taste of penicillin. In one study2 it was the least palatable of 14 commonly prescribed antibiotic suspensions.

Penicillin V dosage:

• Children: 250 mg two or three times daily for 10 days
• Adults: 500 mg two or three times daily for 10 days

In a meta-analysis1 of 19 slinical studies, involving 2450 patients, the clinical failure rate was 11% after 10 days' treatment with penicillin and 5% with various cephalosporins, with a similar rate and severity of side effects. However, cephalosporins and amoxicillin/clavulanic acid cost more than penicillin, which remains effective for the great majority of patients.

• Penicillin VK (Pen-Vee K) versus Other Medications

• 1. Pichichero ME, Margolis PA. A comparison of cephalosporins and penicillins in the treatment of group A beta-hemolytic streptococcal pharyngitis: a meta-analysis supporting the concept of microbial copathogenicity. Pediatr Infect Dis J 1991; 10: 275–81. PubMed
• 2. Ruff ME, Schotik DA, Bass JW, Vincent JM. Antimicrobial drug suspensions: a blind comparison of taste of fourteen common pediatric drugs. Pediatr Infect Dis J 1991; 10: 30–33.
• 3. Park MA, Matesic D, Markus PJ, Li JT. Female sex as a risk factor for penicillin allergy. Ann Allergy Asthma Immunol. 2007 Jul;99(1):54-8. PubMed
• 4. Fonseca PB, Braga JA, Machado AM, Brandileone MC, Farhat CK. Nasopharyngeal colonization by Streptococcus pneumoniae in children with sickle cell disease receiving prophylactic penicillin. J Pediatr (Rio J). 2005 Mar-Apr;81(2):149-54. PubMed
• 5. Busch DF, Kureshi LA, Sutter VL, Finegold SM. Susceptibility of respiratory tract anaerobes to orally administered penicillins and cephalosporins. Antimicrob Agents Chemother. 1976 Oct;10(4):713-20.
• 6. Head TW, Bentley KC, Millar EP, deVries JA. A comparative study of the effectiveness of metronidazole and penicillin V in eliminating anaerobes from postextraction bacteremias. Oral Surg Oral Med Oral Pathol. 1984 Aug;58(2):152-5. PubMed
• 7. Bennet L, Danell S, Berglund J Clinical outcome of erythema migrans after treatment with phenoxymethyl penicillin. Scand J Infect Dis. 2003;35(2):129-31. PubMed
• 8. Pujadas R, Escriva E, Jane J, Galera MC, Fava P, Garau J, Mirelis B. Efficacy of orally administered penicillin V for prophylaxis of experimentally induced streptococcal endocarditis. Antimicrob Agents Chemother. 1987 Oct;31(10):1474-7.
• 9. Josefsson K, Magni L, Nord CE. High dose phenoxymethylpenicillin for preventing endocarditis. Scand J Infect Dis. 1982;14(2):131-3.

Published: June 16, 2008
Last updated: January 07, 2010