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PDAT4 > 15 - Drug Allergies > Flashcards

15 - Drug Allergies Flashcards

1
Q

Pseudoallergic Reaction

A

Adverse DRUG reaction
with
Similar CLINICAL presentation to ALLERGIC reaction

but without involvement of the immune system

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2
Q

Which TYPE of Allergic Reaction?

Antibody Mediated Reaction

MOST COMMON

Requires a previous exposure = INDUCTION

Occurs immediately upon re-exposure = Elicitation

A

TYPE 1

Mediated by:
IgE & Mast Cells

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3
Q

Based on CLINICAL FEATURES, Which TYPE of Allergic Reaction?

URTICARIAL RASH (hives) = most common

NO FEVER IS SEEN

Pruritis / Flushing / Wheezing

ANGIOEDEMA of
face/extremities / tissues

GI Symptoms / Hypotension / ANAPHYLAXIS

A

TYPE 1

Immediate Onset & mediated by IgE / Mast cells

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4
Q

What type of Rash?

characteristic central blanching & red rims

described as WHEALS

A

URTICARIAL rash = HIVES

most common feature of
Type 1 Allergic Reaction

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5
Q

What type of Rash?

Most Common Drug-Induced Rash

Small / well demarcated lesions
that are
FLAT (macule) or RAISED (papule)

A

MACULOPAPULAR RASH

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6
Q

Anaphylaxis Manifestations

ANY DRUG CAN CAUSE ANAPHYLAXIS

A

SKIN = 80-90%
Anaphylaxis generally needs SKIN involvement
Flushing / Pruritus / Uticaria /Angioedema

Respiratory Tract = 70%
Nasal congestion / cough / hoarseness / SOB / wheezing

GI = 40%
Nausea / ab pain / vomiting / diarrhea

CV = 35%
hypotension / dizziness / tachycardia

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7
Q

Biphasic Anaphylaxis** vs **Protracted Anaphylaxis

Time Coarse of Anaphylaxis

A

Biphasic Anaphylaxis
After apparent recovery,
RECURRENCE within 6-10 hours is possible

Protracted Anaphylaxis
Rare, Symptoms PRESIST >24 hours

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8
Q

Mast Cell-Mediated vs Bradykinin-Mediated

ANGIOEDEMA

A

Mast Cell-Mediated Angioedema
TYPE 1 - occurs IMMEDIATELY after exposure
associated w/ uticaria / pruritis / bronchospasm

Bradykinin-Mediated Angioedema
most commonly associated with ACE-Inhibitors
NOT an ALLERGIC RXN
DELAYED onset ~can be years

Angioedema of Bowel Wall
present as colicky ab-pain / vomiting / diarrhea

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9
Q

Criteria for DIAGNOSING ANAPHYLAXIS
when exposure to allergen is
LIKELY

A

NEED 2+ of these SYMPTOMS –> TREAT IMMEDIATELY

Sudden SKIN + MUCOSAL S/sx
hives / itch-flush / swollen

Sudden RESPIRATORY s/sx
SOB / wheeze / cough

Sudden *REDUCED* BP or Symptoms of END-ORGAN dysfxn
COLLAPSE / incontinence

Sudden GASTROINTESTINAL symptoms
cramps / ab pain / Vomiting

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10
Q

Criteria for DIAGNOSING ANAPHYLAXIS
when exposure to allergen is
KNOWN

Exposed to a drug they are allergic to

A

If the allergen is KNOWN:

  • *Just need**
  • *REDUCED BP**

Infants & children:
low systolic BP or >30% decrease in systolic BP

Adults:
Systolic BP <90mmHg or >30% decrease from baseline

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11
Q

Criteria for DIAGNOSING ANAPHYLAXIS
when exposure to allergen is
UNKNOWN

involvement of skin/mucosal tissue or both

A

SUDDEN ONSET OF ILLNESS
ALONG WITH 1 or more of:

Sudden Respiratory Symptoms & signs
SOB / Wheeze / Cough

Sudden reduced BP or Symptoms of END-ORGAN dysfxn
Hypotonia = COLLAPSE / incontinence

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12
Q

Pitfalls to DIAGNOSING ANAPHYLAXIS

A

Signs are NON-SPECIFIC

Skin Manifestations are ABSENT in 10-20%
&
MAY BE ABSENT if H1 Antihistamine taken

Sedated / confused / demented patients
are unable to voice s/sx

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13
Q

What TYPE of ALLERGIC REACTION?

CYTOTOXIC reaction

Drug binds to surface of certain cell types
–> act as antigens
cell is then targeted for lysis by macrophage

Symptoms appear

  • *1 week +** after exposure
  • can be within HOURS if previously exposed*
A

TYPE 2

Delayed onset & caused by IgG mediated Cell destruction

CELL LINE DIES
Hemolytic Anemia
Thrombocytopenia
Leukopenia / Neutropenia
Pancytopenia / Agranulocytosis

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14
Q

HEPARIN INDUCED THROMBOCYTOPENIA
HIT

A

Type 2 Allergic Reaction

Causes:
Paradoxical INCREASED RISK for CLOTTING

  • *AB –> HYPERACTIVE PLATELETS**
    but. ..
  • *AB initiates CLEARANCE –> LOW PLATELETS**

Life + Limb threatening clots

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15
Q

Which TYPE of ALLERGIC REACTION?

IMMUNE-COMPLEX hypersensitivity

Timing:
Occurs with HIGH DOSE / long term / recurrent drug exposure

DELAYED by 1week+ after drug exposure
needs significant titers of AB to generate symptoms

A

TYPE 3

  • *Delayed onset** and caused by IgG
  • *immune-complex desposition –> complement activation**

FREE IgG or IgM –> binds drug
VVV
forms a free/soluble circulating immune comlex
VV
Precipitates in TISSUES –> INFLAMMATORY RESPONSE

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16
Q

Based on CLINICAL FEATURES, Which TYPE of Allergic Reaction?

DRUG FEVER
also seen with type 4 reactions

  • *Vasculitis**
  • *Purpura** (larger) / Petechiae (smaller) = bleeding into skin
  • may also be seen in THROMBOCYTOPENIA in Type 2*

Serum Sickness

A

TYPE 3

Immune-Complex
delayed

Free IgG / IgM binds drug –> complex

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17
Q

What DRUGS are implicated with VASCULITIS?

Vasculitis common with TYPE 3
Pupura / Petechiae / Fever / Uticaria

A

PROPYLTHIOURACIL = PTU
MOST COMMON

  • *Beta Lactams** / Sulfonamides / Phenytoin / Allopurinol
  • may take weeks for resolving after D/C*
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18
Q

How to DISCRIMINATE
DRUG FEVER vs Infectious Fever

Drug fever common with Type 3 Reactions
but also with Type 4

A

Most commonly caused by Antibiotics
fever will stop after D/C of drug, recurs within hours of re-challenge

  • *COMMONLY HIGH_ = _102-104***F
  • BUT*
  • *Patient DOES NOT KNOW they have Fever**

Presense of EOSINOPHILIA
correlated well with drug fever

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19
Q

What TYPE of ALLERGIC REACTION?

  • *CELL-MEDIATED**
  • *T-Cell**, not antibodies

Typically present as SKIN REACTIONS

DELAYED –> occur after 1-3 weeks of treatment

A

TYPE 4

Aka = Delayed Hypersnsitivity Reaction

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20
Q

Based on CLINICAL FEATURES, Which TYPE of Allergic Reaction?

Maculopapular Eruptions

SJS = Steven Johnsons Syndrome

TEN = Toxic Epidermal Necrolysis

DRESS = Drug rash with eosinophilia and Systemic Symptoms

Contact dermatitis

A

TYPE 4
Generally involve the skin, since skin is repository for a LARGE # of T-CELLS

21
Q

Presentation of SJS & TENs

Commonly seen with:
Type 4 Delayed Hypersensitivity

A

Begins with FEVER & MALAISE
VVV
Followed rapidly by ERythmatous / purpuric macules+plaques
VVV
Progress to EPIDERMAL NECROSIS / SLOUGHING

SJS = LESS severe = <10% BSA slough

TEN = >30% BSA slough

SJS-TEN mix = 10-30%

22
Q

MOST COMMONLY IMPLICATED DRUG

for
SJS & TENS

A

Type 4

ANTIBIOTIC SULFONAMIDES

beta lactams

Anticonvulsants

Allopurinol / Abacavir / Nevirapne

NSAIDs

23
Q

Presentation of
DRESS
Drug Rash with Eosinophilia and Systemic Symptoms

A

SEVERE, involves:
Widespread Rash / FEVER >38.5
+
SINGLE or MULTI-ORGAN FAILURE
Liver = most common involved organ

  • NOT all cases are associated with EOSINOPHILIA*
  • *DiHS** is new name

Commonly caused by:
Anti-Epileptics

24
Q

Most commonly implicated drug cause for
DRESS

A

ANTICONVULSANTS

Unique symptom = Organ Failure

Phenytoin / Phenobarbital / Lamotrigine –> hepatitis

Allopurinol / Sulfonamades -> nephritis

Abacavir –> pneumonitis

Olanzapine

25
Q

What UNCLASSIFIED Drug Allergy?

When Ampicillin or Amoxicillin are taken

DURING INFECTION w/ Epstein-Barr Virus = MONO

  • *Red/Itchy Maculopapular rash** –> upper extremeties & trunk
  • can have fever / swelling of lips+eyelids / joint pain*

KEY POINT:
NOT LIKELY TO OCCUR ON RECHALLENGE
after Resolution of infection
not an allergic reaction that persisits

A

AMINO-PENICILLIN REACTION

26
Q

What UNCLASSIFIED Drug Allergy?

Arthralgias is MOST common - 90% of cases (joint pain)

Myalgias present in 50%

Erythemia / Pericarditis / Positive ANA anti-nuclear ABs

need to differentiate from another disease

Onset can be weeks->years after starting drug

RESOLVES RAPIDLY after D/C

A
  • *DILE**
  • *Drug-Induced Lupus**

common in LUPUS but UNCOMMON in DILE:
Malar Rash / Discoid Lesions
RENAL INVOLVEMENT (only seen in LUPUS)
Positive Anti-dsDNA vs positive ANA

27
Q

How to DIAGNOSE
DILE?

Drug-Induced Lupus

A

POSITIVE Anti-Histone AB
WITH
NEGATIVE Anti-dsDNA

anti-dS DNA is common in lupus disease
also renal involvment

28
Q

What drugs are ASSOCIATED with
DILE?

Drug Induced Lupus

A

S H I P P

Sulfas

Hydralazine = high risk

Isoniazid

Procainamide = high risk

Phenytoin

29
Q

What UNCLASSIFIED Drug Allergy?

Commonly implicated with
PPIs

Often associated with:
eosinophilia

A

INTERSTITIAL NEPHRITIS

30
Q

What UNCLASSIFIED Drug Allergy?
and its Common drug cause

Caued by:
Ultraviolet / Visible-light ACTIVATIOn of drug
VV
Sunburn-like reaction

A

DRUG-INDUCED
PHOTOTOXICITY / PHOTOALLERGY

Most commonly caused by:

commonly Doxycycling

Sulfonamides / Voriconazole / Amiodarone

31
Q

Which COMMON INDIVIDUAL AGENT causes this drug allergy?

All 4 types of reactions can occur

Most common is:
Uticaria / Pruritus / Angioedema

A

BETA LACTAMS

MOST COMMON cause of Allergic Drug Reactions
10% of patients

PCN SKIN TEST to confirm

32
Q
  • *PCN SKIN TESTING**
  • *Penzylpenicilloyl Polylysine**
  • *PRE-PEN**
A

Tests for IgE Reaction to PENICILLINS
(Beta Lactam allergy)
People are allergic to the METABOLITE = PRE-PEN

Start w/ EPIDERMAL inj of Pre-Pen
if NO reaction –> INTRADERMAL admin

Need to also give: Histamine & NS

Epinephrine & Diphenhydramine syringes
should be readily available

33
Q

Beta Lactam
CROSS REACTIVITY
with CEPHALOSPORINS

A

1st Gen Cephalospirins (Cephalexin) have
HIGHER RATES OF CROSS REACTIVITY
similar side chains to PCN

Cross reactivity of
2nd / 3rd / 4th gen cephs are VERY SMALL

34
Q

Beta Lactam
CROSS REACTIVITY
with CARBAPENEMS

A

LIKELY <1%

  • *CONSIDER PCN SKIN TESTING**
  • if negative, HIGHLY UNLIKELY that allergy will occur w/ carbapenem*
35
Q

Beta Lactam
CROSS REACTIVITY
with AZTREONAM

A

NO IMMUNOLOGIC CROSS REACTIVITY

PCN allergy –> SAFELY TAKE AZTREONAM

EXCEPT FOR: CEFTAZIDIME
has identical side chain to Aztreonam
= Significant Risk of Cross-Reactivity

36
Q

What to do if a patient with H/O PCN
&
requires a Cephalosporin or Carbepenem

A

1st, determine if patient:

  • *Recieved a CEPH/CARBepenem SINCE** the time of initial PCN reaction
  • if they DID w/ NO REACTION –* > can give med

2nd determine the:
SEVERITY of REACTION

Mild-Moderate & >10 years ago –> May give medication

  • *Anaphylaxis / severe**
  • -> DO NOT give unless test dose or desensitation in ICU
37
Q

Which COMMON INDIVIDUAL AGENT causes this drug allergy?

DELAYED cutaneous macupapular rash within 3 days

Most common cause of:
SJS & TENs

A

SULFONAMIDES
2nd most common cause

ONLY ANTIBIOTIC SULFONAMIDES
due to arylamine side chain

Non-Antibiotic sulfonamides
no significant cross reactivity, RARE to occur

38
Q

Which COMMON INDIVIDUAL AGENT causes this drug allergy?

Acute Hypersensitivity Reaction
similar to TYPE 1 reaction

Samter’s Triad of Symptoms
Hypersensitivity Rxn / Asthma Exacerbation / Rhinitis + Nasal polups

A

ASPIRIN

Cross Rxn w/ NSAIDs are common

little to NO cross reaction with COX-2 inhibitors

39
Q

Which COMMON INDIVIDUAL AGENT causes this drug allergy?

Most common cause of DRESS

Eosinophilia is common
Can develop into –> SJS or TEN
Fever / rash / internal organ involvement

onset occurs several weeks into therapy

A

ANTICONVULSANTS

Anticonvulsant Hypersensitivity Syndrome / DRESS

VERY COMMONLY CAUSED BY:
VALPROATE + LAMATRIGINE
valproate inhibits lamotrigine metabolism
increased risk of hypersensitivity

40
Q

Drugs that REQUIRE
HLA TESTING

A

A-C A P

ABACAVIR

CARBAMEZAPINE

ALLOPURINOL

PHENYTOIN

drugs that require HLA TESTING

41
Q

TREATMENT for Symptoms of UTICARIA

A

Generally self-limiting after D/C of offending agent

Treat Symptoms:
H1 / H2 Anthitamines // glucocorticoids

EPINEPHRINE if H/O of Anaphylaxis

42
Q

Treatment for ANAPHYLAXIS

A

D/C SUSPECTED ANTIGEN/DRUG

  • *IM INJECTION OF EPINEPHRINE**
  • DO NOT DELAY ONCE DIAGNOSED*

Anaphylaxis –> release of histamine –> vasodilation –> drop in BP
to RAISE BP:
Lay patient Down on Back & keep Legs Raised

0.9% NaCl 1-2 L wide open

43
Q

EPINEPHRINE

A
  • NO CONTAINDICATIONS TO EPI FOR ANAPHYLAXIS*
  • *DO NOT DELAY after Anapylaxis Diagnosis**
  • *Alpha & Beta AGONIST**
  • *Vasoconstriction –> ^BP^
  • inhibits FURTHER MEDIATOR RELEASE***
  • *bronchodilation**

Dosing:
IM/SC - 0.3 mg of 1mg/ml q3-5min until improvement
into mid/outer thigh for faster onset

44
Q

Adjunct Therapies to EPInephrine
if Continued URTICARIA

do NOT substitute adjunct therapy for ephinephrine

A
  • *BENADRYL**
  • *25-50 mg IVP**
  • *RANITIDINE**
  • *50 mg IVPB**
45
Q

Adjunct Therapies to EPInephrine
if Continued RESPIRATORY SYMPTOM

​do NOT substitute adjunct therapy for ephinephrine

A

Bronchodialators

  • *Albuterol Nebulized Solution**
  • *2.5 - 5 mg PRN**
  • *Ipratropium Nebulized Solution**
  • *0.5 mg PRN**
46
Q

Adjunct Therapies to EPInephrine
to PREVENT / MINIMIZE LATE-PHASE REACTION

​do NOT substitute adjunct therapy for ephinephrine

A

Corticosteroids

do NOT reverse symptoms ACUTELY
onset of action is 4-6 hours

  • *MethylPrednisolone**
  • *125 - 250 mg IV q6h**

Transition to oral prednisone as pt stabilizes for 3 days of total therapy

47
Q

Treatment for

REFRACTORY ANAPHYLAXIS

A

EPINEPHRINE INFUSION
Slow IV infusion, is mcg (not mg)

Vasopressors
dopamine / dobutamine

  • *IV FLUIDS**
    0. 9% saline
48
Q

What to do AFTER

RECOVERY FROM ANAPHYLAXIS

A

Monitor for 4-6 hours

Transition to –> oral meds

  • *EDUCATE** patient on:
  • *causitive agent / avoid exposure / RECORD**

Consider:
Self Treatment Device = Epipen

49
Q

EPI-PEN or Adrenaclick

A
  • *Adult Version = 0.3 mg IM**
  • *>30 kg**

Kids = 0.15 mg IM

Pull off blue tab –> inject –> then
HOLD IN PLACE FOR 3 SECONDS

PDAT4 (34 decks)

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