Skin & Soft Tissue Infections

Question 1

List the supportive treatment for skin rashes (urticaria) and atopic dermatitis (eczema)

Answer 1

Supportive treatment: (Antihistamine & Corticosteroid)

1st Generation Antihistamine: Refer to PPNP1 Notes

2nd Generation Antihistamine:
o Loratadine (Second generation antihistamine)
o Fexofenadine (Second generation antihistamine)

Corticosteroid (Topical)
o Betamethasone
o Mometasone

(Refer to cutaneous or systemic side effects)
Often used for asthma, hives or lupus.

Question 2

List the causes of common skin irritation such as skin rashes (urticaria) and atopic dematitis (eczema)

Answer 2

Caused by:
Variety of factors,
incl. infections, heat, allergens,
immune system disorders & medications

Question 3

List the common skin infections caused by Group A strep (GAS)
(Group A Streptococcus)

Answer 3

Cellulitis and Decubitus ulcers (bed sores or pressure ulcers)

Question 4

Decubitus ulcers are commonly known as?

Answer 4

Bed sores or Pressure ulcers

Question 5

Name the treatment for Cellulitis or Erysepilas

Answer 5

Antibiotics
- Cephalexin (Class of Cephalosporin),
- Clindamycin (Class of Lincosamide)

(Mostly treated with PO, serious treatment with IV)
If the infection is in the arm or leg, then keeping that limb elevated can help decrease swelling and speed up recovery.

Question 6

Name the treatment for decubitus ulcers aka bed sores or pressure ulcers

Answer 6

Antibiotics used to treat Infection
- Piperacillin-tazobactam (Penicillin)
- Ciprofloxacin (Fluoroquinolone),
- Clindamycin (Lincosamide),
- Vancomycin (Glycopeptide)

Question 7

Why is 2nd Gen H1 antihistamines preferred, over 1st Generation H1

Answer 7

Most 1st H1-antihistamines were introduced before regulatory agencies existed and before clinical pharmacology studies of new medications were required.
Information about pharmacokinetics and pharmacodynamics in healthy adults, elderly people, children, infants, and other vulnerable patients is therefore not available for most of them, and few drug interaction studies have been performed with them.

2nd H1 antihistamines
For most 2nd H1-antihistamines, pharmacokinetics have been extensively investigated in healthy adults, patients with impaired hepatic or renal function, and elderly people, children, and infants. Their drug-drug, drug-food, and drug–herbal product interactions. Examples of second-generation antihistamines are loratadine and fexofenadine

Question 8

List examples of 1st Gen H1 antihistamines

Answer 8

diphenhydramine, hydroxyzine

side effects: drowsiness and anticholinergic effects

Question 9

List examples of 2nd Gen H1 antihistamines

Answer 9

Loratadine and fexofenadine

Question 10

Why are corticosteroids used in the treatment of skin & soft tissue infections?

Answer 10

Corticosteroids are a class of human-made or synthetic drugs used in almost every medical specialty.

They lower inflammation in the body by reducing the production of certain chemicals. At higher doses, corticosteroids also reduce immune system activity.

They come in different potencies (see Table 49.3 Topical Corticosteroids in textbook).

Corticosteroids resemble cortisol, a hormone naturally produced by our body’s adrenal glands.

Cortisol is a major player in a wide range of biological processes, including metabolism, immune response, and stress.
Because corticosteroids ease swelling and irritation, doctors often prescribe them to treat conditions like asthma, hives, or lupus.

Corticosteroids can provide substantial relief of symptoms, but come with the risk of serious side effects, especially if used long term.

Question 11

List the 2 types of antibiotics used to treat skin infections.

Answer 11

Cephalexin (PO) &
Clindamycin (PO/IV) for MRSA patients

Question 12

Skin infections: Cephalexin (PO)

List the class, MOA, rationale for its use, and adverse effects for:
Cephalexin

Answer 12

Class: Beta-lactam antibiotic;
1st generation Cephalosporin

MOA: Inhibits bacterial cell wall synthesis Broad spectrum:

Rationale: Good coverage against bacterial infection caused by Gram +ve and -ve bacteria

A.E.:

Well-tolerated; Rash and diarrhoea most common adverse effect

1-4% patient allergic reaction: severe hypersensitivity are but potentially fatal such as SJSB;

Thrombophlebitis (inflammation at injection site)

Question 13

Skin infections: Clindamycin (PO/IV) for MRSA patients

List the class, MOA, rationale for its use, and adverse effects for:
Clindamycin (PO/IV)

Answer 13

Class: Lincosamide
Protein synthesis inhibitor
(specially on 50S subunit of bacterial ribosome)

MOA: Protein synthesis inhibition

Rationale:
- Broad spectrum: Good coverage against bacterial infection caused by Gram +ve and -ve bacteria,
- anaerobes when less toxic alternatives are not effective options.
- Effective against MRSA.

A.E.: Nausea, diarrhoea, vomiting, headache, constipation
Anaphylaxis, superinfection, myopathy, pseudomembranous colitis

Question 14

Recall the decision triad used in the treatment for decubitus ulcers

Answer 14

The Patient,
The Bug
The Drug

Question 15

List the 4 commonly used antibiotics used for the treatment of Decubitus Ulcers (bedsores)
(Refer to decision triad)

Answer 15

(1) Piperacillin-tazobactam (IV) - Extended Spectrum (anti-pseudomonal)
(2) Ciprofloxacin (PO) - Broad spectrum (BS)
(3) Clindamycin (PO/IV) - MRSA
(4) Vancomycin (PO/IV) - reserved for serious infections, MRSA

Question 16

Skin infections: Decubitus Ulcers (bedsores)

List the class, MOA, rationale for its use, and adverse effects for:
Piperacillin-tazobactam (IV)

This drug is more suitable for which group of patients?

Answer 16

Class: Beta-lactam antibiotic with oxapenams
aminopenicillins

MOA: Inhibits bacterial cell wall synthesis (inhibit transpeptidation)

Rationale: Extended spectrum (anti-pseudomonal)

A.E:
- Well-tolerated;
- Rash and diarrhoea most common adverse effect
- 1-4% patient allergic reaction: severe hypersensitivity are but potentially fatal such as SJS;
- Thrombophlebitis (inflammation at injection site)

Question 17

Skin infections: Decubitus Ulcers (bedsores)

List the class, MOA, rationale for its use, and adverse effects for:
Ciprofloxacin (PO)

This drug is more suitable for which group of patients?

Answer 17

Class: 2nd generation Fluoroquinolones

MOA: DNA synthesis inhibition

Rationale:
- Broad spectrum;
- Pharmacokinetics:
Fluoroquinolones belong to a special class of antibiotics that is concentration-dependent killing. (read this article if interested)

However no longer a first-choice drug as increasing resistance rate

A.E.: Nausea, diarrhoea, vomiting, headache, restlessness, pain and inflammation at injection site

Anaphylaxis, tendon rupture, superinfection, photosensitivity, pseudomembranous colitis, seizure, peripheral neuropathy, hepatotoxicity.

*thus, not suitable for elderly with tendonitis or athletes with ruptured tendon

Question 18

Skin infections: Decubitus Ulcers (bedsores)

List the class, MOA, rationale for its use, and adverse effects for:
Clindamycin (PO/IV)

This drug is more suitable for which group of patients?

Answer 18

Class: Lincosamide, Protein synthesis inhibitor
(specially on 50S subunit of bacterial ribosome)

MOA: Protein synthesis inhibition

Rationale:
- Broad spectrum: Good coverage against bacterial infection caused by Gram +ve and -ve bacteria,
- anaerobes when less toxic alternatives are not effective options. - Effective against methicillin -resistant Staphylococcus aureus (MRSA)

A.E.: Nausea, diarrhoea, vomiting, headache, constipation
Anaphylaxis, superinfection, myopathy, pseudomembranous colitis

Question 19

Skin infections: Decubitus Ulcers (bedsores)

List the class, MOA, rationale for its use, and adverse effects for:
Vancomycin (PO/IV)

This drug is more suitable for which group of patients?

Answer 19

Class: Non-beta lactam; Glycopeptide

MOA: Bacteria cell wall synthesis inhibitor (inhibit transglycosylation)

Rationale:
- In dividing Gram +ve bacteria,
- Reserved for serious infections, MRSA

A.E.: Nausea, vomiting, anaphylaxis, superinfections, nephrotoxicity, ototoxicity and Red Man’s syndrome

Question 20

List the major classes & types of drugs used to treat osteomyelitis (OM) caused by S.aureus

2 groups!

Answer 20

Caused by bacteria (s. aureus)
Antibiotics: Ceftriaxone (Cephalosporin), Vancomycin (Glycopeptide)

Caused by mycobacterium (M. TB)
Antibiotics: Rifampicin, Isoniazid, Pyrazinamide, Ethambutol (RIPE), Vitamin B6

Caused by fungi
Antifungal drugs (not covered)

Question 21

List the major classes & types of drugs used to treat osteomyelitis (OM) caused by M.TB

Answer 21

Caused by mycobacterium (M. TB)
Antibiotics: Rifampicin, Isoniazid, Pyrazinamide, Ethambutol (RIPE), Vitamin B6

Question 22

Bone infections: OM caused by bacteria (s.aureus)

List the 2 different types of antibiotics for consideration.

List the class, MOA, rationale for its use, and adverse effects for:

This drug is more suitable for which group of patients?

Answer 22

**Drug: Ceftriaxone **
Class: Beta-lactam antibiotic;
3rd generation Cephalosporin

MOA: Bacteria cell wall synthesis inhibitor (inhibit transpeptidation1)

Rationale: Broad spectrum: Good coverage against bacterial infection caused by Gram +ve and -ve bacteria

A.E:
-Well-tolerated;
-Rash and diarrhoea most common adverse effect
- 1-4% patient allergic reaction: severe hypersensitivity are but potentially fatal;
- Thrombophlebitis

Question 23

Bone infections: OM caused by bacteria (s.aureus)

List the 1 type of antibiotics for consideration for MRSA patients

List the class, MOA, rationale for its use, and adverse effects for:

This drug is more suitable for which group of patients?

Answer 23

Drug: Vancomycin
Class: Non-beta lactam; Glycopeptide
MOA: Bacteria cell wall synthesis inhibitor (inhibit transglycosylation1)

Rationale:
- In dividing Gram +ve bacteria,
- Reserved for serious infections, methicillin -resistant Staphylococcus aureus (MRSA)

A.E.: Nausea, vomiting, anaphylaxis, superinfections, nephrotoxicity, ototoxicity and Red Man’s syndorme

Red man’s syndrome is a rash above the nipple line due to histamine release when vancomycin is infused too rapidly., sometimes + nephrotoxicity & ototoxicity.

Question 24

Bone infections: OM caused by bacteria (M.TB)
List the drugs used to treat OM caused by MTB

List the class, MOA, rationale for its use, and adverse effects for:

Answer 24

Question 25

What are the considerations before starting the treatment for OM caused by MTB

Answer 25

*Need to check visual acuity to assess toxicity. If patient is not able to perform eye test (eg. under 8 years of age, or red-green colour blindness), Ethambutol can be substituted with Streptomycin (aminoglycosides).

Second line TB drugs are amikacin, ofloxacin, cycloserine (see textbook but not tested; just know for your general knowledge)

1. These are first line drugs (RIPE), similar to treating pulmonary TB. Though more prevalent in developing countries, TB sets off in people who are immunocompromised (HIV, age).
2. These drugs are to be taken as a multidrug regimen to prevent resistance and increase therapeutic success.
3. One of the adverse effects affecting TB treatment outcome is anti-TB drug induced hepatotoxicity.

• Among the first-line anti-TB drugs, isoniazid, rifampicin, and pyrazinamide are known to cause hepatotoxicity, but pyrazinamide attribute to a higher percentage for the drug-induced liver toxicity compared to the other drugs.
• Hepatotoxicity is usually presented and diagnosed with jaundice or a high concentration of liver function marker proteins like aspartate aminotransferase (AST)/alanine aminotransferase (ALT), alkaline phosphatase (APT), or total bilirubin.
• Treatment should be interrupted and, generally, a modified or alternative regimen (start with rifampicin and isoniazid then pyrazinamide) should be used for those with ALT elevation more than three times the upper limit of normal (ULN) in the presence of hepatitis symptoms and/or jaundice, or five times the ULN in the absence of symptoms. An increase in serum ALT is more specific for hepatocellular injury than an increase in AST which can also signify abnormalities in muscle, heart, or kidney.