2. Penicillins

Question 1

Penicillins mechanism of action

Answer 1

Prevents peptidoglycan from cross-linking in bacterial cells wall - therefore bactericidal.

Question 2

Broad spectrum pencillins

Answer 2

1. amoxicillin
2. ampicillin (high bacterial reisistance and should not be used in hospital without a culture/sensitivity test)
3. antipseudomonal pencillins (reserved for serious infections and giving parenterally).

Question 3

Narrow spectrum penicillins

Answer 3

1. Benzylpenicllin (giving parenterally, usually treats meningitis)
2. Phenoxymethylpenicillins (treats strep throat and taken orally QDS)
3. Flucloxacillin reserved for stapphylococcal infections, so is therefore reserved for skin infections. (Can cause choleostatic jaundice so used with caution).

Question 4

Penicillins are typically used to treat

Answer 4

streptococcal, gonococcal and meningococcal infections

Question 5

Benzylpenicllin administration

Answer 5

Benzylpenicllin must be given by injection as it is unstable in gastric acid. Only used in relation to CNS infections in meningitis, as they poorly permeate the blood brain barrier, unelss it is inflammed, this occurs in instances such as meningitis.

Question 6

Phenoxymethylpenicillin (Penicillin V) administration

Answer 6

Suitable for oral administration as it is stable in gastric acid

Question 7

Phenoxymethylpenicillin (Penicillin V) typical indications

Answer 7

Prophylaxis against streptococcal infections following rheumatic fever and prophylaxis against pneumococcal infections following splenectomy in sickle cell disease

Question 8

Alternatives antibiotics that can be used to treat antistapphyloccal infections since benzylpenicllins have now become resistant to them

Answer 8

Anti-stapphylococcal penicillins (Flucloxacillin)

Question 9

Flucloxacillin administration

Answer 9

Can be given orally and by injection as it is acid-stable

Question 10

Adverse reactions associated with flucloxacilln treatment

Answer 10

Cholestatic jaundice and hepatitis may occur up to 2 months following treatment

Question 11

What can alternatively be given in antistapphylococcal infections

Answer 11

Temocillin in gram-negative infections

Question 12

Ampicillin typically treats

Answer 12

Exacerbations of chronic bronchitis, middle ear infections and urinary tract infections

Question 13

Ampicillin counselling advice

Answer 13

Ampicillin must be taken on an empty stomach to increase its absorption

Question 14

Common side effect of ampicillin

Answer 14

Maculopapular rash occur with ampicillin, (not related to a penicillin allergy). More commonly seen in patients with leukaemia or cytomegalovirus infection.

Question 15

Amoxicillin counselling advice

Answer 15

Can be taken with or without food, absorption remains unaffected

Question 16

Amoxicillin typically treats

Answer 16

Respiratory tract infections, H.pylor, CAP, otitis media. Good choice for empirical therapy and want to target a wide range of bacteria. SHOULD NOT be used to blindly treat sore throats, as a sore throat may be caused by glandular fever, where maculopapular rashes are a common symptom. This may confuse for a pencillin allergy.

Question 17

Amoxicillin doses

Answer 17

1-11 months old: 125mg TDS
1-4 years old 250mg TDS
Adult : 500mg-1000mg TDS

Question 18

Clinical significance of co-amoxicalv

Answer 18

Co-amoxicalv is clavulanic acid and amoxcillin. Clavulanic acid makes amoxicillin active against beta-lactamase producing bacteria. Clavulanic acid has no antibacterial activity on its own and can cause choleosatic jaundice.

Question 19

Consequences to other types of therapy if patient has immediate hypersensitivity to pencillins

Answer 19

Patients may also react the same way to cephalosporins

Question 20

Common side effect of co-amoxiclav

Answer 20

Choleostatic jaundice - more common in patients above the age of 65. Jaundice is usually self-limiting and rarely fatal

Question 21

Examples of anti-pseudomonal penicillins

Answer 21

Piperacillin (+ tazobactam)

Ticarcillin (+ clavulanic acid)

Question 22

Co-amoxiclav should be used with caution

Answer 22

In patients with hepatic impairment

Question 23

Anti-pseudomonal pencillins spectrum of activity

Answer 23

Broad spectrum against both gram negative and gram positive bacteria, and anaerobes

Question 24

Anti-pseudomonal pencillins are typically used to treat

Answer 24

septicaemia, hospital acquired pneumonia, and infections involving the skin, soft tissues or intra abdomen

Question 25

What are anti-pseudomonal pencillins typically given with and why?

Answer 25

Aminoglycosides to achieve a synergistic effect

Question 26

Common Side effects of pencillins

Answer 26

Hypersensitivity, diarrhoea (more common in broad spectrum antibiotics), vomiting, skin reactions

Question 27

Patients that are at higher risk of of anaphylactic reactions to penicillins

Answer 27

Patients with asthma, hay fever and eczema

Question 28

Patients that should not receive a penicillin

Answer 28

Patients with a history of anaphylaxis, urticaria, or rash immediately after administration of penicillins. Should not recievee any beta -lactam antibiotics.

Question 29

Patients that can still receive a penicillin

Answer 29

Patients with a history of a minor rash, non-confluent, non-pruritic rash restricted to a small area of the body or a rash that occurs over 72 hours after penicillin administration. Penicllins should only be used for serious infections, in these patients.

Question 30

Penicllins should NEVR be administered via…

Answer 30

INTRATHECALLY, can damage the brain

Question 31

Flucloxacillin should be used with caution

Answer 31

In patients with hepatic impairment

Question 32

Apropriateness of pencillins in pregnancy

Answer 32

Penicillins are suitable for use in pregnancy

Question 33

Penicillin interactions

Answer 33

Are generally safe antibitiotics but
1. Reduce the renal clearance of methotrexate, raising its levels and therefore risk of toxicity

2. Increase the anticoagulant effect of warfarin by killing normal gut flora, that synthesize vitamin K
3. Flucloxacillin and Clavulanic acid (in co-amoxiclav) are hepatotoxic drugs. Increased risk of hepatotoxicity when two or more hepatotoxic drugs are taken at the same time.

Examples of hepatotoxic drugs include anti-epileptics (carbamazepine and valproate), anti-fungals (fluconazole), isoniazid, methotrextate, statins, sulfasalazine, tetracycline drugs