Tetracyclines

Question 1

Mechanism of action of tetracyclines

Answer 1

Broad spectrum + bacteriostatic

Binds to ribosomal 30s subunit and inhibits bacterial protein synthesis

Question 2

Key counselling points for tetracyclines (3)

Answer 2

DECREASED ABSORPTION

1) Doxycycline, Lymecycline and minocycline (DOES LIKE MILK) - Do not take indigestion remedies, or medicines containing iron or zinc, 2 hours before or after you take this medicine
2) Oxytetracycline, tetracycline, demeclocycline - Do not take milk, indigestion remedies, or medicines containing iron or zinc, 2 hours before or after you take this medicine

PHOTOSENSITIVITY
- Avoid exposure to sunlight/sunlamps - Demecloccyline and doxycyline

OESOPHAGEAL IRRITATION
- Swallow whole with plenty of fluid during meals while sitting or standing - Doxycycline (caps), minocycline (caps/tabs), tetracycline (tabs)

Question 3

Pregnancy

Answer 3

Avoid - skeletal development, may cause discolouration of childs teeth, maternal hepatoxicity in large doses

Question 4

Contraindications

Answer 4

Children <12 can bind to bone and teeth, posible staining and detail hypoplasia

Question 5

Side effects

Answer 5

Benign intracranial HTN - stop if headache and visual disturbances
Tooth discolouration
Exacerbation of lupus

Question 6

Two specific SEs of minocycline

Answer 6

Irrversible pigmentation and lupus

Question 7

Key interactions

Answer 7

Isotretinoin - increased risk of benign intracranial HTN
Lithium - increased risk of lithium toxicity
Warfarin - possibility of enhanced AC effect
Statins - hepatic failure, hepatitis