Allergy Capital

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Immunotherapy - Practical Aspects

Immunotherapy is an effective and safe treatment for allergic rhinitis, asthma (in selected patients) and venom allergy as long as precautions are taken.

General Precautions

Administration should be supervised by a physician who must be in attendance at the time of injection. Resuscitation facilities must be available. Allergen solutions will normally be marked with the patient's name, content, concentration and expiry date. Allergens should be stored in the refrigerator AWAY from the freezer section. Frozen solutions loose allergenicity & should be replaced.

Waiting Period

Patients are routinely advised to wait for at least 30 minutes after each injection for aero allergens, and for at least 45 minutes after venom injection. They should be instructed to report any symptoms suggestive of an allergic reaction to the injection such as generalized itch or rash, gut upset, difficulty breathing or dizziness.

Contraindications for Immunotherapy

• Exacerbation of asthma
• Severe intercurrent infection
• Current use of beta blockers (oral/topical)
• Any patient in whom adrenaline would be contraindicated.eg. MAOI use

Administration

• Check the size of the last reaction & modify dose if needed (see below).
• If patient has asthma, check baseline peak flow or spirometry (should be > 80% of usual best)
• Store allergen in fridge (do NOT freeze).
• Shake bottle gently to resuspend allergen
• Draw up exact dose into single use insulin syringe (0.5 ml / 50 unit syringe, or 1.0 ml / 100 unit syringe). Double-check NAME, STRENGTH and DOSE carefully.
• Administer subcutaneously to outer aspect of upper arm, around half way between elbow and shoulder. Draw back plunger before injecting; the dose should NOT be given intravenously.
• Patient should wait for at least 30 minutes (45 minutes for venom) after the injection.
• Record size of the local reaction (swelling); Patients can take an antihistamine to treat local reactions if necessary.
• Record baseline peak flow; observe for an additional hour if it drops > 10%.
• Patient should avoid vigorous exercise that day to minimize risk of reactions.

Schedule for Increasing the Dose

Never exceed the dosage schedule, as the rationale is to slowly build up tolerance to injections & minimize the risk of adverse reactions. In patients where there is difficulty increasing the dose because of LOCAL side-effects, please telephone to discuss the regimen. In some cases where only LOCAL reactions are experienced, a prophylactic antihistamine may allow some patients to tolerate the injections more easily.

• Interval since last injection <14 days, increase the dose according to the planned schedule.
• Interval since last injection >14 days, give the same dose as last time & do not increase it.
• Interval since last injection 3-6 weeks, give half the previous dose.
• Interval since last dose >6 weeks, the patient should be re-assessed by the specialist

TREATMENT OF ADVERSE REACTIONS TO IMMUNOTHERAPY

Equipment Required

Stethoscope, sphygmomanometer, tourniquet, needles and large bore needles (14 gauge), adrenaline HCL 1ml ampoules of 1:1000, equipment for administering oxygen (8L/min), equipment for administering i.v. fluids (Haemacell, N saline), oral airway, antihistamine, corticosteroids for injection.

Local Reactions

Patients can take an antihistamine to reduce the severity and size of local reactions. Sometimes splitting the dose half into each arm will help. If large local reactions are a problem, please telephone to discuss management.

• weal size <5cm: continue planned schedule
• weal size 5-10cm: hold dose
• weal size >10cm: return to last dose which caused no reaction
• Swelling >5-10cm lasting > 12 hours: return to last dose which caused no reaction

Systemic Reactions

These are of much greater significance. Please ALWAYS telephone me to discuss these reactions, and do NOT give any further immunotherapy injections until you have done so.

Mild Systemic reactions (e.g. cough, sneeze, hay fever-like symptoms, itch, hives, asthma)

• Treat as needed with antihistamines, Ventolin, or adrenalin.
• Give a oral antihistamine as well (eg. Claratyne, Telfast or Zyrtec), even if parenteral phenergan is given.
• Keep the patient under observation until they are well PLUS an extra 60 minutes.
• If in ANY DOUBT about the stability of the patient, give adrenalin and call an intensive care ambulance.
• Apply tourniquet above injection site
• Check BP and pulse
• If needed, add in:
  - Adrenaline adults 1/1000 0.3-0.5 ml IMI; children 0.01 mL/kg (max 0.3mL)
  - Ventolin by nebuliser or 4 puffs via spacer and repeat as necessary
  - Prednisone 50mg/day (adults); 25mg/day (children) if needed.
• Telephone me to discuss the reaction before giving any further allergen injections

Anaphylactic Shock

• Place patient in recumbent position. Elevate legs if possible
• Adrenaline as above
• Apply tourniquet above injection site to slow systemic absorption
• Insert IV line, administer Haemacel or Normal saline if hypotensive
• Clear air passage and give oxygen 8 litres / minute
• Nebulised Ventolin or equivalent if bronchial obstruction present
• Phenergen imi
• Hydrocortisone 200 mg i.v.
• Monitor BP and pulse and continue treatment accordingly
• Send for intensive care ambulance