Page 632 - Clinical Immunology_ Principles and Practice ( PDFDrive )

608 Part FIVE Allergic Diseases

experiencing SRs should seek medical advice and should be associated with a higher rate of side effects compared with
medically observed until the symptoms resolve and blood pressure conventional protocols. Most systemic side effects are mild; only
is stable. one-third of patients require medical treatment.
Mild reactions confined to the skin may be treated with Premedication with antihistamines reduces large local and
rapid-acting oral antihistamines alone. If respiratory or cardio- other cutaneous reactions, such as urticaria, but severe SRs may
vascular symptoms occur, intramuscular epinephrine must be not be suppressed. Some units routinely give antihistamines 2
given immediately, intravenous (IV) access should be established, hours before up-dosing injections until the maintenance dose
and antihistamines and corticosteroids given intravenously has been repeatedly well tolerated. In patients with recurrent
(Chapter 42). All patients with severe SRs should be hospitalized SRs during up-dosing, off-label use of anti-IgE (omalizumab)
and supervised until they recover completely. Patients with has made it possible to complete up-dosing and to continue
cardiovascular symptoms must be treated and transported in maintenance VIT. 31
the supine position, and IV volume replacement is indicated.
Subsequently, every patient who has experienced a systemic Efficacy of VIT
allergic sting reaction should be investigated with a view to In addition to three prospective controlled trials, the efficacy of
prevention measures and immunotherapy. 10 VIT has been confirmed by well-tolerated sting challenges during
1,10
VIT in several uncontrolled prospective studies. Full protection
Emergency Medication Kit is achieved in 80–85% of patients receiving bee venom and in
All patients with a history of SRs should carry an emergency kit 95–100% of patients receiving Vespula venom. The higher risk
30
for self-administration. After a sting, patients should immediately of treatment failure in bee venom allergy may relate to differences
take both antihistamines and corticosteroids, whether or not in venom compositions. Important allergens, such as Api m10
symptoms occur. In case of systemic symptoms, such as urticaria, or Api m 3, may be missing or present in low concentrations in
32
dyspnea, generalized weakness, or dizziness, epinephrine should some VIT products. It has therefore been suggested that patients
be administered intramuscularly via an autoinjector, such as the with a predominant sensitization to these allergens may not be
30
Epipen (dosage 0.3–0.5 mg of epinephrine). In children with properly protected by VIT. 33
body weight <25 kg, Epipen Junior (0.15 mg epinephrine) or The efficacy of immunotherapy with commercially available
an equivalent product should be administered, along with half whole-body extract of the ant Solenopsis has not been documented
the adult dose of antihistamines and corticosteroids. If any SR in controlled studies. However, excellent results, comparable with
occurs, medical care must be sought immediately. those of VIT with Vespula venom, were obtained in a double-blind
placebo-controlled study using M. pilosula venom. 4
Venom Immunotherapy 1,10
Indications Duration of VIT 17
Venom immunotherapy (VIT) is indicated in children and adults Lifelong treatment may be the safest recommendation, but in
with a history of severe SRs (grade III/IV), provided sensitization most allergy centers, VIT is given for up to 5 years. If VIT is
to the relevant venom has been demonstrated by skin and/or given for at least 3 years, >80% of both adults and children are
blood test. LLRs or unusual reactions do not require VIT. VIT still protected, when reassessed 1–7 years after discontinuation.
is also recommended for patients who experience repeated mild, Longer courses of treatment should be considered in high-risk
non–life-threatening reactions and are at high risk for reexposure, patients, such as those with very severe systemic sting reactions,
such as beekeepers or their family members. Concomitant coexisting cardiovascular or pulmonary disease, and systemic
cardiovascular disease, mastocytosis, and strongly impaired quality allergic reactions to VIT or stings during VIT and in subjects
of life because of the venom allergy are relative indications for with elevated basal serum tryptase levels. Lifelong VIT is advised
VIT in patients with non–life-threatening sting reactions. 19,24 for patients with cutaneous or systemic mastocytosis. 10
Contraindications for VIT are the same as for immunotherapy
with other allergens (Chapter 91). Risk Factors for Recurrence of SRs After Stopping VIT
A number of risk factors have been identified for relapse of
Dosage and Treatment Regimens Hymenoptera venom allergy after discontinuation of VIT : in
17
The recommended maintenance dose for both children and adults general, adults, especially older people, because of concomitant
is 100 µg of the venom. This maintenance dose is equivalent to diseases, have a less favorable prognosis compared with children.
approximately two bee stings or several vespid stings. A higher Patients with bee venom allergy have a higher relapse risk
dose (e.g., 200 µg) is recommended when SRs occur after compared with those allergic to Vespula venom. Patients with
29
reexposure to a field sting or a sting challenge. In highly exposed more severe pretreatment reactions and those with more SRs
subjects, such as beekeepers or professional gardeners, a main- during VIT (to injections or field stings) have a higher risk for
tenance dose of 200 µg is advised. recurrent SRs to Hymenoptera stings. The risk of relapse is lower
VIT may be initiated by a conventional or an ultra-rush after 5 years of VIT, compared with only 3 years of VIT.
protocol. During the first year, maintenance VIT is given every
4 weeks. Subsequently, the intervals may be extended to 6 weeks ALLERGIC REACTIONS TO BITING INSECTS
if VIT is well tolerated.
Biting insects may cause local allergic reactions as a result of
Adverse Reactions to VIT sensitization to their salivary proteins introduced during the
The overall incidence of systemic adverse reactions to VIT varies process of blood sucking. Systemic reactions are very rare. The
1,10
between 5% and 40%. VIT with bee venom causes side effects responsible insects belong to the orders Diptera, Hemiptera, and
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more often than with Vespula venom. Ultra-rush protocols are Siphonaptera (Fig. 43.3). 34