GENERIC NAME: penicillin V (phenoxymethyl penicillin)

BRAND NAMES: Pen-Vee-K; Veetids

DRUG CLASS AND MECHANISM: In 1928, Alexander Fleming noted that mold belonging to the genus Penicillium, inhibited the growth of bacteria. Fleming called this unknown antibacterial substance penicillin. Ten years later, a group at Oxford University began to investigate the material in laboratory mice. Penicillin was hailed as a miracle drug and saved countless lives in World War II. Today, many derivatives of penicillin have been developed which inhibit more types of bacteria than this original, life-saving drug. Penicillin itself is active against Streptococci (including Streptococcus pneumoniae), Listeria, Neisseria gonorrhoeae, Clostridium, Peptococcus, and Peptostreptococcus. Most staphylococci now are resistant to penicillin.

PRESCRIPTION: yes

GENERIC AVAILABLE: yes

PREPARATIONS:: Tablets: 125mg; 250mg; 500mg. Oral solution: 125 mg/5mL; 250 mg/5mL.

STORAGE: Tablets should be kept between 15°C (59 °F) and 30°C (86°F). The solution should be kept refrigerated, and can be used for up to 14 days after it is reconstituted by the pharmacist. It must be shaken before each use and should be kept well sealed.

PRESCRIBED FOR: Oral penicillin V is effective against susceptible bacteria causing throat infections, laryngitis, bronchitis, and pneumonia. Only mild to moderate infections are treated with oral penicillin. Patients with more severe infections can be given penicillin by injection (intramuscular "shots" or intravenously). Penicillin also is given to prevent infection on the valves of the heart in patients with certain diseases of the heart valves who are having dental work or undergoing gastrointestinal endoscopic procedures. (Dental work and some endoscopic procedures can introduce bacteria into the blood, and these bacteria may infect the valves.)

DOSING: Penicillin V is ideally given 30 to 60 minutes before meals, but can be given with meals to persons who develop nausea or stomach pain with it. On the other hand, penicillin G (a type of penicillin which is rarely used today) must be given on an empty stomach. Penicillin is most often given four times a day for 7 to 14 days. When given to prevent infections in persons undergoing dental or gastrointestinal procedures, penicillin is given as one dose one hour prior to the procedure, and one more dose is given 6 hours later.

DRUG INTERACTIONS: Probenecid (Benemid) causes an increase in the level of penicillin in the blood by reducing the elimination of penicillin by the kidneys. In fact, sometimes probenecid is combined with penicillin so that a smaller amount of penicillin results in higher blood levels.

PREGNANCY: Penicillin is considered safe during pregnancy.

NURSING MOTHERS: Penicillin is excreted in breast milk. No side effects have been reported in nursing infants whose mothers have taken penicillin. Concern for side effects such as allergic reactions, of course, exist. Thus, physicians must weigh the potential risk versus the benefit.

SIDE EFFECTS: Penicillin generally is well tolerated. Between 1% and 10% of all people are allergic to penicillin. Allergic reactions range from a mild rash to moderate-to-severe hives to severe anaphylactic shock. (In anaphylactic shock, the windpipe swells so that breathing is difficult and the blood pressure falls greatly. Anaphylactic shock is a life-threatening emergency that requires immediate treatment.) Anaphylactic shock occurs in approximately 1 in 3,000 persons who are exposed to penicillin; death occurs in approximately 1 in 50,000 persons who are exposed to penicillin. Persons who are allergic to other penicillin products (such as ampicillin or amoxicillin) are generally considered to be allergic to penicillin as well. Persons who are allergic to the cephalosporin class of antibiotics (e.g., Ceclor, Keflex, Cefzil) may or may not be allergic to penicillins.

Last Editorial Review: 12/31/1997

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