Antibacterial Drugs:
**Mechanisms of action ( site of action )
1. Nucleic acid synthesis inhibition: e.g
Sulphonamides, trimethoprim, quinolones, nitrofurantoin,
refampicin.
2. Protein synthesis inhibition:e.g.
Macrolides, aminoglycosides, Chloramphenicol, tetracycline
3. Cell wall synthesis inhibition: e.g
Vancomycin, cephalosporins, penicillins.
** The β – lactam antibiotics:
These are the pencillines and cephalosporines whose basic
structure include β – lactam ring
Resistance is commonly due to bacterial enzyme called β –
lactamases (( pencillinase and cephalosporinase )) which can
cleave the ring and inactivate the antibiotic.
** The penicillins:
All penicillins are bactericidal with wide range of activity for both
gram +ve and certain gram –ve organism
It should never given interathecally
Their adverse effects include:
1. skin rash
2. anaphylaxis
3. drug fever
4. interstitial nephritis
5. haemolysis
** Benzylpenicllin:
It is rapidly absorbed following intramuscular injection and
excreted by the kidneys withen few hours and addition of
probenecid will delay its excreation and allow smaller doses with
less frequent
** Procain Penicillin: addition of procainamide, given i.m,
Active against: streptococci, meningococci, anthrax, tetanus,
syphilis and diphtheria.
** Phenoxymethyl penicillin; (( Penicillin V ))
Incompletely absorbed from the stomach
Active against: streptococci.
** Cloxacillin & flucloxacillin:
They are stable to staphylococcal β – lactimases
For oral therapy flucloxacillin is superior to cloxacillin
** Temocillin:
It is active against pencillinase producing gram –ve bacilli.
** Ampicillin;
It has a bactericidal action against both gram +ve and certain gram
–ve organisms
It is susceptible to degradation by β – lactimase and not well
absorbed with food.
Skin rash in patients with infectious mononucleosis
** Amoxycillin:
It is an analog of ampicillin which has similar antibacterial
spectrum but it is more reliably absorbed from GIT
** Augmentin
It is a combination of amoxicillin and sodium clavulanate
Clavulanic acid is a potent inhibitors for many β – lactemases and
it can protect amoxicillin from inactivation by them.
** Ticarcillin:
It is an analogue of carbencillin with more activity against
Pseudomonus spp.
A combination of ticarcillin and clavulanic acid is called Timentin.
** Mezlocillin, azlocillin and pipracillin;
They have a wider range of activity and more effective against
many gram –ve bacilli.
The Cephalosporins;
1
st
generation e.g cephalexin, cephradin
2
nd
generation e.g cephaclor, cefuroxime
3
rd
generation e.g cefotaxime, cephitrixone
4
th
generation e. g cefepime, cefpirome
Wide range of activity
10 % of penicillin sensitive may als allergic to them
** Imipenem:
Β- lactam antibiotic with a very broad spectrum which include
aerobic and anaerobic gram +ve and gram –ve organisms.
The Macrolide antibiotics
** Erythromycin:
Used in treatment of infection caused by gram +ve organisms in
penicillin allergic patients.
It is effective in Whooping cough, pneumonia, mycoplasma and
Chlamydia.
S/E : diarrhea, vomiting, abdominal pain, and cholestatic jaundice.
**Clarithromycin:
Greater activity than erythromycin and higher tissue concentration.
** Azithromycin:
More activity against gram –ve organisms including H. Influenzae.
** Spiromycin:
A macrolide used in treatment of Txoplasmosis.
The Tetracyclines: is a bacteriostatic agent used in Brucellosis,
mycoplasma, typhus fever, Q – fever
It should not prescribed for pregnant female, children and patients
with renal failure.
The aminoglycosides:
They include gentamycin, streptomycin, amikacin
Active against gram –ve bacilli
Streptomycin has anti TB and used in treatment of Brucellosis
They are nephrotoxic and ototoxic
Neomycin is too toxic to be given parantraly and used orally in
hepatic encephalopathy.
*** Chloramphenicol:
It is effective in enteric fever and against H. Influenzae
It may cause pancytopenia
It should never be given to premature infant or to the newborn
because of the risk of development of gray baby syndrome.
*** Clindamycin / Lincomycin
Effective against most gram +ve organisms including penicillin
resistant staphylococci
It pentrate well into bones so it is useful for osteomyelitis and
effective in lung abscess
Common cause of pseudomembranous colitis
** Sodium fusidate
It is useful in infection caused by penicillin resistant staphylococci
It is well absorbed and the oral rout can be used instead the
parenteral rout
** Spectinomycin
Used for treatment of gonorrhoea if penicillin is contraindicated
because of allergy or bacterial resistance.
Vancomycin and teicoplanin:
Used for serious staphylococcal infectionincluding methicillin
resistant and it is used in antibiotic associated colitis.
They are nephrotoxic and ototoxic
** Sulphonamides/ Trimethoprim / Co – trimoxazol
Used in treatment of cystitis, UTI, typhoid fever and pneumonia
S/E skin rash, nephritis and haemolysis
*** Quinolone antibiotics
Ciprofloxacin is the most important one
Effective against aerobic gram –ve bacilli.
Used in treatment of typhoid fever, UTI, gonorrhoea
They are contraindicated in children and pregnancy
** Metronidazole
Effective against anaerobic bacteria and intestinal protozoa e.g
Giardia Lambelia and Entameba histilytica.
** Tinidazole
It is similar to metronidazole but with longer half life
*** Antituberculous drugs
Refampicin, INH, Pyrazinamide, Ethambutol and Streptomycin
*** Antifungal drugs
For topical application: Nystatin, Clotrimazol
For oral administration: Ketoconazole, Grisofulvin
For intravenous infusion: Amphotericin, Flucytocin
*** Antiviral drugs
Acyclovir: effective against herpes simplex and H. zoster
Famciclovir: antiherpes agent with activity against E B virus
and hepatitis B virus
Ganciclovir: antiherpes agent with activity against
cytomegalovirus
Amantadine: used for prophylaxis of influenza A.
Ziduvidine used for HIV infection.
Ribavirine: against RNA viruses e.g Influenza, RSV
***Antiparasitic drugs:
Antimalarial: Chloroquine, premaquine, proguanil
Anti intestinal protozoa: Metronidazole, tinidazole
Antihelmenth drugs: Mebendazole, Albendazole
Antibilharzial agents: Praziquantel.