A Textbook of Clinical Pharmacology and Therapeutics

CONTACT LENS WEARERS

As the number of patients who wear contact lenses increases,
an awareness has developed that these patients represent a
special subgroup in whom particular care is needed when
prescribing, as they may develop specific additional problems
related to commonly prescribed drugs. A summary of such
agents is given in Table 52.6.

FURTHER READING

Ghate D, Edelhauser HF. Ocular drug delivery. Expert Opinion on Drug

Delivery2006; 3 : 275–87.

Marquis RE, Whitson JT. Management of glaucoma: focus on pharma-

cological therapy. Drugs and Aging2005; 22 : 1–21.

CONTACTLENSWEARERS 429

Table 52.6:Common drug-induced problems in patients with contact lenses

Drug Adverse effects Comment

Oral contraceptives (high oestrogen) Swelling of the corneal surface – poorly Visual acuity deterioration

fitting lenses

Anxiolytics, hypnotics, first-generation Reduced rate of blinking Dry eyes and higher risk of infections

antihistamines (e.g.

diphenhydramine, etc.)

Antihistamines, anticholinergics, Reduced lacrimation Dry eyes – irritation and burning

phenothazines, diuretics and

tricyclic antidepressants

Hydralazine and ephedrine Increased lacrimation

Isotretinoin, aspirin Conjunctival inflammation and irritation

Rifampicin and sulfasalazine Discolour lenses

Case history

A 68-year-old man has hypertension and ischaemic heart

disease. His angina and blood pressure are well controlled

while taking oral therapy with bendroflumethiazide, 2.5 mg

daily, and slow-release diltiazem 120 mg daily. His visual

acuity gradually declines and he is diagnosed as having sim-

ple open-angle glaucoma. His ophthalmologist starts ther-

apy with pilocarpine 2% eye drops, one drop four times a

day, and carteolol drops, two drops twice a day. A week

after starting to see his ophthalmologist he attends his GP’s

surgery complaining of shortness of breath on exertion,

paroxysmal nocturnal dyspnoea and othopnoea. Clinical

examination reveals a regular pulse of 35 beats per minute,

blood pressure of 158/74 mmHg and signs of mild left ven-

tricular failure. His ECG shows sinus bradycardia with no evi-

dence of acute myocardial infarction.

Question

How can you explain this problem and what should your

management be?

Answer

Carteolol is a non-selective β-adrenergic antagonist that can

gain access to the systemic circulation via the nasolachrymal

apparatus thus avoiding heptic first-pass metabolism. It can

thus act (especially in conjunction with a calcium antagonist –

diltiazem in this case) on the cardiac conducting system and

on the working myocardium. Discontinuing the ocular carte-

olol should resolve the problem.

Key points

Drugs used to lower intra-ocular pressure

• Systemic administration of:
  
  
  • osmotic agents (e.g. mannitol);
  
  
  • acetazolamide (carbonic anhydrase inhibitor).
  
  
  
  


• Topical administration of:
  
  
  • pilocarpine (muscarinic agonist);
  
  
  • timolol (β-adrenoceptor antagonist);
  
  
  • dorzolamide (carbonic anhydrase inhibitor);
  
  
  • latanoprost (PGF 2 αanalogue);
  
  
  • brimonidine (α 2 -agonist).