someone say:" when i was baby , i have given penicillin , and i had terrible hives , the pediatrician told my parent dont give me penicillin again , because i will die "
so hx is important in determining pencillin allergy in patients
important things to ask in hx are (in drug hx )
1-isolated git upset(diarrhea , nausea , vomiting ,abdominal pain
2-cough
3-itching (pruritus)
4-rash (and type of rash )
5-time-onset <4hr (immediate)
6-the treatment that have been given to treat this allergy (antihistamine , penicillin discontinued)
, even though , there are 3 types of pencillin allergy test :
1-oral challenge
2-intradermal
3-skin prick
so before doing any of those tests , you should classify the patient according to risk of penicillin allergy
1-low risk (can do oral challenge ) 2-moderate risk(can try one of those three tests) 3-high risk(dont test him/her)
1-low risk are those who say i am allergic to penicllin but when do focus hx you will find that he took augmentin antibiotic course last year , also those have previous intolerance (like nausea ,vomiting ,diarrhea , headache ) rather than true allergy
2- moderate risk :pregnant , unstable or compromised hemodynamically-or compromised respiratory status , those considered at least moderate risk to have penicillin allergy
3-high risk: pt who develop severe reaction to penicillin ( blistering rash is specific ,hemolytic anemia ,fever , thrombocytopenia , nephritis , hepatitis , joint pain , anaphylaxis)
preparing pt for penicillin allergy test:
1-betablocker should hold for 2 days before test(betablocker inhibit epinephrine during anaphylaxis) , you can use glucagon as betablocker antidote
2-antihistamine should hold for 5days(pt shouldnt take antihistamine drug for 5 days before)
3-tricyclic antidepressant - antipsychotic drug have strong antihistamine activity and their effect last for weeks after stopping the medication
4-immunosupressant like steroid , interfere with allergy test (most likely delayed response , also may interfere with IgE reaction that control the allergy reaction
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5- check vitals , also if available , check peak flow meter
6-before do the test , you should have anaphylaxis kit (1mg/1ml im adrenaline , prednisolone 20mg tab , benadryl (diphenhydramine 25mg tab) , pepcid (h2 receptor blocker 20mg tablet) , also should have iv fluid , bronchodilator
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for low risk pt , you can do oral amoxicillin test (250-500mg capsule) and observed for minimum 1hr
check vital signs every 30mins
proceed to direct oral test if pt report isolated reaction that unlikely to be allergic , like headache , git upset , pruritus without rash , family hx of penicillin allergy ,
headache , git upset , pruritus without rash(sign of pt anxiety )
anaphylaxis : Management
anaphylaxis involve 2 or more systems
cutaneous : flushing , itching , urticaria , hives , swelling
respiratory : cough , nasal congestion , runny nose ,wheezing , sob , chest tightness
cardiovascular : faintness, tachycardia ,chest pain , tunnel vision , hypotension , loss of consciousness , sense of impending dooms
git: nausea , vomiting , diarrhea , abdominal pain (cramp)
*low blood pressure alone , with know allergen exposure , considered anaphylaxis
epinephrine used to abort urticarial reaction and prevent deterioration
if pt have anaphylaxis :
1- lay pt supine , elevate legs
2-airwat-bteathing-circulation-vitals
3-im epinephrine , iv fluid , adjunctive medications
*when doing skin allergy test , bruising may seen with pt who take antiplatelet-anticoagulant drug
*you should wait 15min after skin prick
*in positive penicillin allergy , pt should avoid penicillin , cephalosporin , carbapenem
*negative penicillin allergy not role out cephalosporin allergy and vice versa
*allergy to augmentin , may due to allergy to clavulanic acid not penicillin , and may to penicllin so pt should undergo penicillin allergy test to determine the source of allergy
(+ histamine (idle +test to compare with pp)) (- negative , using saline) (pp the allergen used such as penicillin)