Doxycycline

Question 1

Drug class?

Answer 1

Tetracyclines

Question 2

How does it work?

Answer 2

Bacteriostatic – inhibit protein synthesis.
Clinically effective in the treatment of a variety of infections caused by a wide range of gram-negative and gram-positive bacteria, as well as certain other micro-organisms.

Question 3

Indications?

Answer 3

• Respiratory tract infections – strep pneumoniae, haemophilus influenzae, klebsiella pneumoniae.
• UTIs – klebsiella species, enterobacter species, E.coli, strep faecalis.
• STIs – chlamydia trachomatis.
• Dermatological infections – acne vulgaris.
• Chronic prostatitis, syphilis, chronic bronchitis exacerbation.

Question 4

Conta-indications?

Answer 4

Tetracycline deposition in bone/teeth, children <12, pregnancy/breastfeeding.

Question 5

Side-effects?

Answer 5

Nausea, vomiting, diarrhoea, anorexia, flushing, tinnitus, dysphagia, oesophageal irritation.
May increase muscle weakness in myasthenia gravis.

Question 6

Possible interactions?

Answer 6

• Carbamezapine/phenytoin: ↑doxycycline metabolism.
• Methotrexate: ↑risk of methotrexate toxicity
• Milk reduces absorption.