Tetracyclines

It is important to note that the use of tetracyclines does not increase Staphylococcus aureus resistance (see MRSA).

How do tetracyclines work?

As antibiotics, tetracyclines interfere with protein bacteria.

• It must be taken when upright and with copious water, to reduce photosensitiser and can cause unexpected sunburn or acute painful onycholysis
• It can cause nausea, vomiting, and diarrhoea; it is better tolerated when taken after food than on an empty stomach
• Women prone to vulvovaginal candidiasis (thrush) with broad-spectrum antibiotics should consider topical or systemic azole antifungal agent

Minocycline has an increased risk of severe adverse effects compared to doxycycline, so it best to avoid minocycline as a first-line agent. These include:

Minocycline is less likely than doxycycline to cause photosensitivity.

Drug interactions with tetracyclines

Important drug interactions of tetracycline and its derivatives include:

• Risk of raised intracranial hypertension is increased if taken with other drugs with the same side effect such as systemic retinoids (acitretin, isotretinoin, alitretinoin)
• Reduced bioavailability of tetracyclines with iron, aluminium, magnesium, calcium, rifampicin, celestipol, and anticonvulsants
• Increased renal toxicity with diuretics
• May increase lithium concentrations, which can lead to toxicity

Effect on contraceptives

There is little evidence that tetracyclines reduce the efficacy of the oral contraceptive pill unless they cause gastrointestinal upset. However, to be absolutely safe, extra precautions should be taken, particularly in the first four weeks of starting the antibiotics. Discuss this with your doctor.