Tetracyclines Flashcards
Are tetracyclines broad-spectrum?
Yes, activity against gram (+) and gram (-); used to cover anaerobes but has limited usefulness now due to increasing resistance
What is a unique characteristic of tetracyclines that makes them useful in treating intracellular infections?
Tetracyclines accumulate intracellularly, making them useful in the treatment of intracellular bacteria and parasites eg chlamydia, coxiella, brucella
Tetracyclines are the treatment of choice for which infections? (10)
- Chlamydia
- trachoma
- psittacosis
- salpingites
- urethritis
- lymphogranuloma venereum
- Rickettisa
- Brucella
- Spirochete infections (Borrelia burgdorferi, leptospirosis if penicillin allergy)
- Respiratory and genital mycoplasma infections
- Acne
- Destructive periodontal disease
- Exacerbations of chronic bronchitis (due to activity against H.influenza)
- MRSA
- Anthrax
Which tetracyclines are available in the NHS? (6)
- Doxycycline
- Minocycline
- Demeclocycline
- Lymecycline
- Tigecycilne
- Oxytetracycline
Which tetracycline is notable for having a broader spectrum of activity?
Minocycline; active against N.meningitidis and has been used for meningococcal prophylaxis (no longer recommended due to side-effects and greater risk of drug-induced lupus)
What are the main side effects of tetracyclines? (5)
- Photosensitivity
- Hypersensitivity
- Tooth enamel discoloration or hypoplasia
- Hepatotoxicity
- Intracranial HTN causing headache and visual disturbances
Can tetracyclines be given during pregnancy or breastfeeding?
NO; due to effects on skeletal development in the first trimester AND association with tooth discoloration when used in the second or third trimester
Maternal hepatotoxicity also reported with large parenteral doses
*exception is when travel to malarious areas is unavoidable during pregnancy; doxycycline can be used for malaria prophylaxis if other regimens are unsuitable, and if the entire course of doxycycline can be completed before 15 weeks’ gestation
When taking tetracyclines, patients should be advised to avoid what lifestyle and environmental factors? (3)
- Exposure to sunlight or sun lamps (photosensitivity)
- Alcohol (increases risk of hepatotoxicity)
- Antacids, milk, oral iron (decrease absorption when taken together with oral tetracyclines)
Do tetracyclines affect the efficacy of oral contraception?
Not according to the NHS (only abx known to directly effect the efficacy of oral contraception are rifampicin and related drugs eg rifabutin);
However, according to Mayo Clinic, oral contraception containing estrogen may not work properly while taking tetracycliens, therefore unplanned pregnancies may occur
Advise female patients taking oral contraception to use a different or additional means of birth control while taking tetracyclines
https://www.mayoclinic.org/drugs-supplements/tetracycline-class-oral-route-parenteral-route/precautions/drg-20069585
What are the contraindications of tetracyclines?
- Pregnancy
- Breastfeeding
- Children 12 yo or younger
Caution in renal impairment
In which two chronic conditions should tetracyclines be prescribed with additional caution?
- Myasthenia gravis (may increase muscle weakness)
2. SLE (may exacerbate)
What is the primary route of administration for tetracyclines?
Oral
What additional monitoring requirements should be used for minocycline?
If treatment continued for longer than 6 months, monitor every 3 months for hepatotoxicity, pigmentation and for systemic lupus erythematosus—discontinue if these develop or if pre-existing systemic lupus erythematosus worsens
