A Textbook of Clinical Pharmacology and Therapeutics

• an antibiotic (e.g. co-amoxiclavorclarithromycin), if
  bacterial infection is strongly suspected – beware potential
  interactions with theophylline, see below;


• if the patient fails to respond and develops increasing
  tachycardia, with increasing respiratory rate and a fall in
  PaO 2 to 8 kPa or a rise in PaCO 2 to 6 kPa, assisted
  ventilation will probably be needed;


• sedation is absolutely contraindicated, except with
  assisted ventilation.


• general care: monitor fluid/electrolyte status (especially
  hypokalaemia) and correct if necessary.

CHRONIC ASTHMA

The primary objectives of the pharmacological management of
chronic asthma are to obtain full symptom control, prevent exac-
erbations and achieve the best possible pulmonary function,
with minimal side effects. The British Thoracic Society/Scottish
Intercollegiate Guideline Network (BTS/SIGN) have proposed
a five-step management plan, with initiation of therapy based
on the assessed severity of the disease at that timepoint. Figure
33.2 details the treatment in the recommended steps in adult
asthmatics. Step 1 is for mild asthmatics with intermittent symp-
toms occurring only once or twice a week; step 2 is for patients
with more symptoms (more than three episodes of asthma symp-
toms per week or nocturnal symptoms). Step 3 is for patients
who have continuing symptoms despite step 2 treatment and
steps 4 and 5 are for more chronically symptomatic patients or
patients with worsening symptoms, despite step 3 or 4 treatment.

PRINCIPLES OF DRUG USE IN TREATING

CHRONIC ASTHMA

1. Metered dose inhalers (MDIs) of β 2 -agonists are
   convenient and with correct usage little drug enters the
   systemic circulation. Aerosols are particularly useful for
   treating an acute episode of breathlessness. Long-acting
   β 2 -agonist (e.g. salmeterol) should be taken regularly with
   top-ups of ‘on-demand’ shorter-acting agents. Oral
   preparations have a role in young children who cannot
   co-ordinate inhalation with activation of a metered-dose
   inhaler. Children over five years can use inhaled drugs
   with a ‘spacer’ device. There are several alternative
   approaches, including breath-activated devices and
   devices that administer the dose in the form of a dry
   powder that is sucked into the airways.
   2.Patients should contact their physician promptly if their
   clinical state deteriorates or their β 2 -agonist use is increasing.
   3.Inhaled glucocorticosteroids (e.g. beclometasone,
   fluticasone,budesonide) are initiated when symptoms
   are not controlled or when:
   
   
   • regular (rather than occasional, as needed) doses
     of short-acting β 2 -agonist bronchodilator are
     required;
   
   
   • repeated attacks interfere with work or school.
   
   
   
   

Adverse effects are minimized by using the inhaled route.

Severely affected patients require oral glucocorticosteroids

(e.g.prednisolone).

234 THERAPY OF ASTHMA,COPD AND OTHER RESPIRATORY DISORDERS

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Figure 33.1:Pathophysiology of asthma and sites of drug action. PAF, platelet-activating factor; LTs, leukotrienes; PGs, prostaglandins.