Pharmalgen® is an option for the treatment of IgE-mediated bee and wasp venom allergy in those who have had [www.nice.org.uk/TA246]:
- a severe systemic reaction to bee or wasp venom;
- a moderate systemic reaction to bee or wasp venom PLUS:
- a raised baseline serum tryptase concentration,
- a high risk of future stings,
- or anxiety about future stings.
Comes as an initial treatment set, with graded doses, plus a maintenance set. For treatment, start with subcut at 1000th of SPT threshold dose or 10th of intradermal threshold, increase every 3-7 days until a threshold is reached. Rush or modified rush regimens also available. Then maintain maximum tolerable dose (typically 100mcg) at 4 weekly intervals initially, gradually extending, for at least 3 years.
If symptoms or signs of hypersensitivity to therapy develop (e.g. rash, urticaria, bronchospasm, faintness), even if mild, the child should be observed until these have resolved completely. [BNFc] High baseline tryptase may make reactions to immunotherapy more likely – but still appropriate to do.
Asthma is not a contraindication but severe asthma (specified as FEV persistently below 70% despite treatment) is.
No age cut off, but data “sparse” for children under 5.
Some patients tolerate venom immunotherapy well but still have systemic reactions! So challenge tests with subcut venom not reliable – use live insect! Done sometimes to identify candidates for immunotherapy, or to identify those on maintenance immunotherapy to see who is not yet protected esp at high risk of sting or high risk of fatal reaction.
Efficacy of immunotherapy is related to adherence to treatment! High adherence at 5 years to subcut immunotherapy. Recent contraindications more flexible than previous ones. New guidelines in preparation. [Pitsios, Allergy 2015;70:897]
Venom immunotherapy is 95% effective against wasp, 80% against bee. Consider VIT if mild reaction but high tryptase, high risk of sting or major QOL issue. But kids have better prognosis so only VIT for most severe. Don’t do VIT without positive test. Usual duration of VIT in UK is 3 yrs.