Penicillins,quinolones And Tetracyclines Flashcards
(28 cards)
The 5 classes of penicillins
1) Beta lactamase sensitive (benzoyl penicillin G (PEN G) and phenoxymethylpenicillins (PEN V)
2) Penicclinase resistant penicillin (Flucloxacillin)
3)Broad pectrum penicillin( Amoxicillin, Ampicllin, co-amoxiclav)
4) Antipseudomonal penicillin (piperacillin, ticarcillin)
5) Mecillinam- type pivmecillinam
Penicillins
Drug action: Bactericidal and interfered with cell wall synthesis
Caution: history of allergy
Side effects- Hypersensitivity
- Diarrhoea(frequently occurs with the oral route, most common with broad spectrum penicllins, which can cause antibiotic associated colitis)
- Intrathecal injections: Avoid this route for penicllins as it can cause encephalopathy
Penicillins allergy and cross sensitivity
- hypersensitivity
- Allergic reactions occurs in 1-10% of individuals
- anaphylactic reactions occur in fewer than 0.05%
- Higher risk of anaphylaxis in patients with history of asthma, eczema and hayfever
- Avoid in patients with history of anaphylaxis
Penicllins - main contraindications
- patients with a history of penicllins allergy
- Patients allergic to one penicillin is most likely allergic to all
- Cross sensitivity(cephalosporins and other beta lactase antibiotics, avoid these antibiotics)
- General rule of thumb vs common side effects
- Allergy = stop penicllins and change to macrolide, anaphylaxis, hive and an immediate rash occurs
- avoid cephalosporins and beta lactam antibiotics
- minor side effects - continue penicllins - rash after 3 days, minor small rash non itchy
Benzylpenicllin
- Benzylpenicllin(Pen G) is inactivated by beta lactamases
- indication- sore throat infections, otitis media, cellulitis, pneumonia, anthrax, strep infections and meningitis
- inactivated by gastric and absorption from GI tract is low and therefore must be given by injection
Penicllins - Pen G
Important safety information -intrathecal injection not recommended
Caution - accumulation of sodium from injections can occur with high doses
Side effects - Fever
Pregnancy and Breastfeeding - not known to be harmful
Renal impairment - High doses may cause neurotoxicity (including cerebral irrationally, convulsions or coma)
Phenoxymethypenicllin
- Similar to pen G in activity but a little less active
- Gastric stable so suitable for oral admin
- Indicated principally for respiratory infections in children,oral infections, tonsillitis, otitis media, cellulitis, strep infections and acute sinusitis
- Side effects - coagulation disorders, increased risk of infection, neurotoxicity, oral disorders
Pregnancy and breastfeeding - not harmful
Cautionary labels 9,23
Broad spectrum penicllins
Ampicillin active against certain gram positive and negative organisms
- indicated by penicillanases
- Many staphylococci strains are now resistant to ampicillin (don’t use for hospital patients without checking sensitivity)
- can be given orally but less than half absorbed, absorption further decreased by the presence of food in the gut so we take before food
- Main indications - chronic bronchitis, middle ear infections and UTIs
Ampicllin side effects
,aculopapular rashes - with both Ampicllin and amoxicillin
- Pregnancy and breastfeeding feeding - not known to be harmful Renal impairment
Label 9,23
Amoxicillin
- derivative of Ampicllin with similar antibacterial spectrum
- Maculopapular rash - commonly occurs surgery Ampicllin and amoxicillin
- better absorbed by mouth than Ampicllin which provides higher plasma and tissue concentrations.
- Absorption- not affected by food
- indications: (UTI, Otitis media, sinusitis, uncomplicated community acquired pneumonia, salmonellosis, oral infections, Lyme disease, anthrax, dental absess, h.pylori
- pregnancy and breastfeeding - not known to be harmful Renal impairment
Cautionary label 9
Important amoxicillin interactions
- allopurinol: increases the risk of skin rash with amoxicillin
- methotrexate: increases risk of toxicity with methotrexate
- Warfarin: amoxicillin alters anticoagulat effects of warfarin
WAM
Broad spectrum - Beta lactamase
Co- amoxiclav
- amoxicillin with clauvulanic acid( beta- lactamase inhibitor)
- Reserved for infections caused by amoxicillin resistant beta lactamase producing strains
- pregnancy not known to be harmful Renal impairment
- caution - Cholestatic jaundice - do not exceed 14 days
Flucloxocillin
Indication- effective against infections caused by penicllins resistant staphylococci (impetigo,otitis externa, cellulitis, pneumonia
- acid stable, therefore can be given orally as well as by injections
- well absorbed from the gut
Flucloxacillin Safety information
Hepatic disorders - Cholestatic jaundice and hepatitis may occur very rarely up to 2 months after fluclox has been stopped
- Admin for more than 2 weeks with increasing age is a risk factor
Flucloxacillin advice
Do not use patients with a history of hepatic failure associated with Flucloxacillin
- Caution in patients with hepatic impairment
- Careful enquiry should be made about hypersensitivity reactions to beta - lactam antibacterials
Alternative for penicillin allergy
Macrolides!!! Or doxycycline
Quinolones Examples
Nalidixic acidm norfloxacin, ciprofloxacin, ofloxacin(uncomplicated UTI, Respiratory tract infections, bone and joint infections, gonorrhoeal, GI. Infections)
Avoid in MRSA infections are they are not effective
Quinolones safety information
- may induce convulsions(lowers seizure threshold) in patients with or without a history of convulsions
- Taking NSAIDs at the same time may induce convulsions
Tendon Damage -
Tendon damage (including inflammation and rupture) in patients within 48hrs of starting treatment
- Patients greater then 60 have a higher risk of tendon damage
- Concomittant use of corticosteroid can also increase risk of tendon damage
- Discontinue quinolones immediately if tendinitis is suspected
Contraindications of Quinolones
History of tendon damage associated to quinolones
Caution:
- Avoid exposure to excessive sunlight (discontinue if photosensitivity occurs)
- Can prolong QT intervals (increase seizure risk)
- Patients with history of epilepsy and seizures
Important things about quinolones
-In children and growing adolescents - not recommended. Can cause arthopathy (joint disease eg. Arthritis)
- Discontinue drug is psychiatric,neurological(hallucinations) or hypersensitivity reactions occur - including severe rash)
Pregnancy - avoid, causes arthropathy
Cautionary labels 7,9,25
Quinolones important interactions
1) NSAIDs - increase risk of seizures
2) Prednisolone - increases the risk of tendon damage
3)Drugs that prolong QT interval or cause arrhythmias (eg.amiodarine,SSRIs,Macrolides, antipsychotics)
Tetracyclines
Broad spectrum antibiotics(value decreased due to resistance)
-Baacteriostatic
- Common indications - Acne,pneumonia, chlamydia, Rickettsia)
- Also used in MRSA infections
- All tetracyclines are similar and little to chose from except Minocycline
Minocycline
- has a broader spec
- Greater risk of lupus like syndrome (photosensitive rash,swelling, unexplained fever etc
- sometimes cause irreversible pigmentation
