Penicillin

Pharmacology

Penicillin, the first ß-lactam antibiotic, renders the synthesis of sensitive bacterial cell wall impossible and is thus bactericidal. Benzylpenicillin (penicillin G) is used parenterally; phenoxymethylpenicillin (penicillin V) is not inactivated to the same degree in the stomach and is therefore used as an oral preparation. The spectrum of action contains most of the Gram-positive bacteria and Gram-negative cocci, different spirochaetes, and Actinomycetes israeli. Enterococci, staphylococci and Gram-negative bacili (e.g. E. coli) are usually resistant. Certain strains of gonococci and pneumococci are also resistant. Phenoxymethylpenicillin generally has more limited activity than benzylpenicillin.

Indications

Benzylpenicillin administered intravenously is the drug of choice for bacterial meningitis if this disease is caused by sensitive strains of meningococci or pneumococci. Further important indications for an intravenous penicillin treatment are endocarditis caused by Streptococcus viridans, other hazardous streptococcal infections (severe pneumonia, arthiritis), neurosyphilis, actinomycosis, anthrax and clostridium infections.

Smaller doses are administered intramuscularly. A streptococcal pharyngitis can be treated with a single injection of a benzylpenicillin slow release preparation (if available). Erysipelas, fusospirochaetes angina (Vincent's angina), diphtheria, pneumococcal pneumonia and primary syphilis infections can also be treated intramuscularly. Secondary prophylaxis of rheumatic fever has become very rare.

Orally administered phenoxymethylpenicillin is a 'painless' alternative for streptococcal angina and other indications of the intramuscular therapy, as well as dog and cat bites. It can be considered in the early stages of Lyme disease if doxycycline is contraindicated.

Adverse Reactions and Interactions

Severe penicillin hypersensitivity with anaphylactic shock is very rare and occurs mostly in connection with parenteral administration (5 to 10 cases on 10000 treated subjects). The emergency treatment is based primarily on adrenaline (and, in addition, maybe intravenous corticosteroids, aminophylline).

However, hypersensitive skin reactions (skin rashes, urticaria) are frequent (1 to 7% of the treated subjects). High concentrations of cerebrospinal fluid are neurotoxic (lethargy, confusion, myoclonia, convulsions). A sterile abscess can occur at the area of the i.m. injection. Hemolytic anemia, nephritis and liver granuloma are very rare complications. Massive i.v. doses are associated with a risk of an electrolyte and volume overload.

Oral preparations occasionally cause nausea, vomiting or diarrhea.

Interactions

In vitro penicillin can inactivate aminoglycosides. Probenecid inhibits the tubulary secretion of penicillin.

Contraindications

None except hypersensitivity to penicillin

Cautions

If a meningococcal infection is suspected, parenteral penicillin therapy ought to be started as quickly as possible.

Risk Groups

Pregnant women: Can be given. Penicillin is considered the safest antibiotic during pregnancy.

Nursing mothers: Can be given. Concentrations in breast milk are relatively low. The risk of an alteration of the child's intestinal flora or of a hypersensitization cannot be excluded.

Children: Intravenously for severe infections: 0.2 to 0.5 million U/kg/day in 4 to 6 doses. Oral (penicillin V): 100,000 U/kg/day in two doses (a maximum of 1.5 million U/day).

Elderly people: No dose reduction is necessary if renal functions are normal.

Renal failure: Creatinine clearance less than 50 ml/min: reduce dose by 25 to 50%; clearance less than 10 ml/min: reduce dose by 50-75%.

Liver insufficiency: No dose adjustment necessary.

Penicillin

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Types of Penicillin

Ampicillin
Oxacillin
Cloxacillin
Dicloxacillin

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Penicillin Today

Penicillin TodayHave you ever been to the doctor and then to the chemist and brought home some pink medicine that tasted like fruit? That was probably penicillin . Alexander Fleming discovered penicillin by accident 70 years ago and Howard Florey and his team made it into a life saving medicine over 55 years ago. Penicillin was the first antibiotic. It killed harmful bacteria that caused infections. Before penicillin, people died from simple infections. Now they can be cured in a matter of days.

Types of Penicillin

Penicillin is available in liquid, capsules, tablets and injections. The liquid penicillin is flavoured to taste like fruit so young children will enjoy taking their medicine. Any medicine with "cillin" at the end of its name is a type of penicillin. Synthetic penicillin is also known as Ampicillin, Oxacillin, Cloxacillin and Dicloxacillin.

Use of Penicillin

TodayEven though now there are also many other antibiotics available, penicillin is still given to patients to fight certain bacterial infections. If you have a viral infection, penicillin or other antibiotics do not work. They kill bacteria not viruses. However, sometimes viral diseases are accompanied by bacterial infections. For example, people with the 'flu' can develop pneumonia caused by bacteria. The virus infection weakens the body's defences, so that bacterial infections can easily start. When this happens, antibiotics are of value.

Production Today

Even though there has been an enormous amount of research into antibiotics in the last 50 years, penicillin is still produced in much the same way as it was in 1943.

Penicillin is not made from the same mould that Howard Florey used in the 1940’s. Instead of Penicillium notatum , Penicillium chrysogenum is used because it produces more penicillin. It is now made in large amounts in enormous vats.

Some bacteria have become resistant to penicillin. Before long these bacteria multiply and the infection becomes uncontrollable by penicillin. To help overcome this scientists have developed a [ semi-synthetic ] penicillin. To do this they change the penicillin molecule and produce a range of penicillin drugs that fights particular bacteria more effectively.

How much is made each year?

Penicillin is still manufactured in large amounts. Approximately 50 million kilograms is produced world wide each year. You only require a small amount of penicillin to cure a small infection. Adult dosage is 250 to 500 mg every 6 hours for 10 days. Dosage for a child is 25 to 90 mg depending on their weight. There are a lot of dosages in 50 million kilograms. Penicillin is still used daily in every country in the world.

Penicillin Today