Penicillin

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Penicillin V is an antibiotic in the penicillin group of drugs. It fights bacteria in your body.
Penicillin V is used to treat many different types of infections caused by bacteria, such as ear infections,.
Penicillin V may also be used for other purposes not listed in this medication guide.
Most widely used antibiotic throughout the world.

Source:Fungus-
• Penicillium notatum.
• Penicillium crysogenum(Commercial source)
Natural penicillin:Benzyl penicillin/PenicillinG
It is a β-lactam drug.
β-lactum antibiotics:
1) Natural penicillins:Benzylpenicillin,Phenoxymethyl penicillin.
2) Penicillinase-resistant penicillin:Methicillin,flucloxacillin.
3) Aminopenicillins:Ampicillin,Amoxycillin.
4) Cephalosporins:1st to 4th generation compunds.
5) Monobactams:Aztreonam.

Classifications of penicillins:

[A]On the basis of source:
a) Natural penicillin:Benzyl penicillin,Penicillin G,Penicillin V,Phenoxy methyl penicillin.
b) Semisynthetic penicillin:Ampicillin,Amoxycillin.

[B]On the basis of spectrum coverage:
a) Narrow spectrum:Penicillin G.
b) Broad spectrum:Amipicillin,Amoxycillin,Carboxy penicillin,Nafcillin,Ticarcillin.

[C]On the basis of acid lability:
a) Acid labile:Penicillin G.
b) Acid stable:Ampicillin,Amoxycillin.
[D]On the basis of β-bactamase enz sensitivity:
a) β-bactamase sensitive:Penicilin.
b) β-bactamase resistant:Cloxacilin,Flucloxacililin,Nafcillin,Oxacillin,Methicillin.

[E]On the basis of duration of action:
a) Short acting:Penicillin G.
b) Intermediate acting:Procain penicillin.
c) Long acting:benzathene penicilln.

Name of natural/semi-synthetic:

[A]Natural:
a) Parenteral:Penicillin G(Benzyl penicillin)
b) Oral:Phenoxymethyl penicillin(Penicillin V)

[B]Semi-synthetic:
a) Parenteral:
• Methicillin.
• Nafcillin.
• Oxacillin.
• Piperacillin.
• Ticarcillin.
• Crystalline sodium penicillin G.
• Potassium penicillin G.
b) Oral:
• Ampicillin.
• Amoxycillin.
• Cloxacillin.
• Flucloxacillin.

Medical uses

The term “penicillin” is often used generically to refer to benzylpenicillin (penicillin G), procaine benzylpenicillin (procaine penicillin), benzathine benzylpenicillin (benzathine penicillin), and phenoxymethylpenicillin (penicillin V).
Procaine penicillin and benzathine penicillin have the same antibacterial activity as benzylpenicillin but act for a longer span of time. Phenoxymethylpenicillin is less active against gram-negative bacteria than benzylpenicillin. Benzylpenicillin, procaine penicillin and benzathine penicillin are given by injection (parenterally), but phenoxymethylpenicillin is given orally.

Mechanism of action of penicillin:

[A]By inhibiting the transpeptidase enzyme→So the final cross linking step (transpeptidation) in the synthesis of peptidoglycan is blocked→Cell wall becomes porous→Water enters the bacteria through the porous cell wall due to high osmotic pressure inside the bacteria→Bacteria s well & burst out→Bacteria are killed.
[B]Penicillin binds to the penicillin binding protein(PBP) in bacterial cell wall & membrane→Some PBP act as transpeptidase→So their actions are blocked.
[C]Penicillin indirectly activates the autolytic enzymes called murein hydrolase/ peptidoglycan hydrolase→Degradation of peptidoglycan→Bacteria are killed.
So penicillins is a bactericidal drug.It can kill those bacteria which are actively growing.They can not kill inactive bacteria.

Pharmacokinetics of penicillins:

[A]Route of administration:Oral,Parentral(IV/IM).
[B]Distribution:Widely disributed if meninges are inflamed.It can cross BBB and enter in CSF.
[C]Plasma half life:usually <2 hrs.
[D]Elimination:Mainly renal and rapidly occurs.90% by tubular secretion.

What happens if I miss a dose?

Take the missed dose as soon as you remember. If it is almost time for your next dose, skip the missed dose and take the medicine at your next regularly scheduled time. Do not take extra medicine to make up the missed dose.
What happens if I overdose?
Seek emergency medical attention if you think you have used too much of this medicine.
Overdose symptoms may include confusion, behavior changes, a severe skin rash, urinating less than usual, or seizure (black-out or convulsions).

What should I avoid while taking penicillin?

Antibiotic medicines can cause diarrhea, which may be a sign of a new infection. If you have diarrhea that is watery or has blood in it, call your doctor. Do not use any medicine to stop the diarrhea unless your doctor has told you to.

Penicillin side effects

Get emergency medical help if you have any of these signs of an allergic reaction to penicillin V: hives; difficulty breathing; swelling of your face, lips, tongue, or throat. Call your doctor at once if you have any of these serious side effects:
• diarrhea that is watery or bloody;
• fever, chills, body aches, flu symptoms;
• easy bruising or bleeding, unusual weakness;
• urinating less than usual or not at all;
• severe skin rash, itching, or peeling;
• agitation, confusion, unusual thoughts or behavior; or
• seizure (black-out or convulsions).
Less serious penicillin V side effects are more likely to occur, such as:
• nausea, vomiting, stomach pain;
• vaginal itching or discharge;
• headache;
• swollen, black, or “hairy” tongue; or
• thrush (white patches or inside your mouth or throat).

What other drugs will affect penicillin?

Before taking penicillin V, tell your doctor if you are using any of the following drugs:
• methotrexate (Rheumatrex, Trexall); or
• probenecid (Benemid).
This list is not complete and there may be other drugs that can interact with penicillin V. Tell your doctor about all the prescription and over-the-counter medications you use. This includes vitamins, minerals, herbal products, and drugs prescribed by other doctors. Do not start using a new medication without telling your doctor.

Limitation of penicillin G:

1) Narrow spectrum:Only act on gram +ve bacteria.
2) Acid labile:Hydrolyzed by gastric acid,so can not be given.
3) Inactivation of drug by β-lactamase enzyme of bacteria,so the bacteria become resistant to the drug.
4) Plasma half life is very short:20-30 min.
5) As given parentrally,these is increased chance of hypersensitivity reaction.
6) Penicillin inj. Is painful.
7) Can not act on-Pseudomonas.

Indications of penicillin:

1) Sterptococcal skin infection:Tonsilitis.
2) Staphylococcal infection.
3) Pneumococcal infection.
4) Meningoccal meningitis.
5) Sever infection:
• Tetanus.
• Diptheria.
• Gas gangrene.
6) Previous used:
• Gonorrhoea.
• Syphilis.

Adverse effects of penicillin:

1) Anaphylactic shock.
2) Interstitial nephritis/Nephrotoxicity.
3) Seizure,encephalopathy.
4) Skin rash.
5) Angio-neurotic edema.
6) Joint swelling.
7) Fever.
8) Nausea,vomiting,diarrhoea.
9) Intense pruitus.
10) Hemolytic anaemia.
11) Leucopenia.
12) Thrombophlebitis,Vasculitis.
13) Hepatitis(mild reversible).

Anti staphylococcal penicillins:

  • Flucloxacillin.
    • Nafcillin.
    • Cloxacillin.
    • Methicillin.
    Penicillin resistance:
    a) Production of β-lactamase enzyme that opens the β-lactum ring→No action of penicillin.
    b) Absence of some penicillin binding receptor due to chromosomal mutation→ Penicillin can not bind with receptor→No action on penicillin.
    c) failure of penicillin to activate the autolytic enzyme in the cell wall→No autolysis of cells.
    Resistance of amoxicillin can be overcome by the β lactamase inhibitor. Amoxycillin+Clavulanic acid.

Prophylactic use of penicillin:

1) Group A streptococcus infection & rheumatic fever.
2) Syphilis.
3) Gonorrhea.
4) Subacute infective endocarditis.
5) Tetanus.
6) Gas gangrene.
7) Anthrax.
8) Before cathetarization.
9) Before tooth extruction
10) Close camping.

Advantage of semi-synthetic penicillin to penicillin G:

1) Less allergic reaction.
2) Suitable oral forms.
3) Broade spectrums.
4) β-lactamase resistant.
5) More & adequate plasma half life.

 

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