A Textbook of Clinical Pharmacology and Therapeutics

Key points
Treatment of anaphylactic shock
Anaphylactic shock is a medical emergency and its
treatment is as follows:
• Stop the offending drug or blood/blood product infusion.
• Check the patient’s blood pressure (lie them flat) and
check for the presence of stridor/bronchospasm.
• Administer oxygen (FiO 2 40–60%).
• Administer adrenaline (epinephrine) 0.5–1 mg
intramuscularly, and repeat after ten minutes if
necessary.
• Give intravenous colloids (0.9% NaCl) for refractory
hypotension.
• Administer hydrocortisone, 100–200 mg i.v.
• Administer chlorpheniramine, 12.5 mg i.v.
• Give nebulized salbutamol, 2.5–5 mg for refractory
bronchospasm.
DRUGS THAT BLOCK THE EFFECTS OF
MEDIATORS OF ALLERGY
Therapeutic approaches to the management of allergic disease
produced by mediators include the following:
• inhibition of their biosynthesis;
• blockade of their release;
• antagonism of their effects.
INHIBITION OF BIOSYNTHESIS OF
PRO-INFLAMMATORY MEDIATORS
INTRANASAL AND TOPICAL
GLUCOCORTICOSTEROIDS
These are covered in Chapters 33 and 40.
CHEMICAL MEDIATORS OF THE IMMUNE RESPONSE AND DRUGS THAT BLOCK THEIR ACTIONS 405
Table 50.2: Properties of commonly used H 1-antagonists
Uses
These preparations are used in the therapy of allergic rhinitis and
they are very effective in reducing the symptoms of nasal itching,
sneezing, rhinorrhoea and nasal obstruction (they are more effective
than cromoglicate). Common agents used to treat hay fever
include beclometasone, budesonide and fluticasone.
Adverse effects
The adverse effects of all these preparations are similar,
namely sneezing, and dryness and irritation of the nose and
throat. Occasionally, epistaxis is a problem.
BLOCKADE OF RELEASE OF PRO-INFLAMMATORY
MEDIATORS
SODIUM CROMOGLICATE AND NEDOCROMIL
See also Chapter 33.
Uses
Sodium cromoglicate and nedocromil are effective in preventing
exercise-induced and allergic asthma (but less effective
than inhaled glucocorticosteroids for the latter). They are
also effective in preventing hay fever and its symptoms.
Cromoglicate is used as nasal or eye drops for allergic rhinitis
and conjunctivitis. Local adverse effects include occasional
nasal irritation or transient stinging in the eye.
ANTAGONISM OF THE EFFECTS OF
PRO-INFLAMMATORY MEDIATORS
ANTIHISTAMINES
There are a large number of antihistamines (H1-receptor antagonists)
available, several of which are available without prescription.
Some of those in common use are listed in Table 50.2. Their
Drug Duration of Degree of Anti-emetic Risk of ventricular tachycardia
First generation
effect (h) sedation action when prescribed with other drugs
inhibiting their metabolism
Promethazine 20 Marked Some ?
Diphenhydramine 6 Some Little ?
Chlorphenamine 4–6 Moderate Little ?
Cyclizine 6 Some Marked ?
Triprolidine
(slow release)
24 Moderate Little ?
Second generation
Acrivastine 6–8 Nil Little None
Fexofenadine 12 Nil Little None
Cetirizine 24 Nil Little None
Loratadine 24 Nil Little None