12. Tetracyclines and glycylcyclines

Question 1

Tetracyclines duration

Answer 1

Short acting

Long acting

Question 2

Short acting Tetracyclines

Answer 2

Tetracycline

Question 3

Long acting Tetracyclines

Answer 3

Doxycycline

Minocyclins

Question 4

Tetracycline
Doxycycline
Minocyclins

Answer 4

Protein synthesis inhibitor S30 subunit - reversible inhibition (inhibits tRNA binding mRNA complex)
4 fused rings with conjugated double bonds

Spectrum: Broad G+ive and G-ive aerobes, Rickettsia, Brucella, (doxycycline: Chlamydia and acne), MRSA, Yesenia, coxiella

Mechanism of resistance: Efflux pump
Ribosome alteration

Administration: Oral or IV (once a day due to long elimination half-life)
Distribution: Concentrate in liver, bille, kidney, gingival fluid and skin | bind to tissues undergoing calcification. (Doxycycline and minocycline enter CNS)
Metabolism: Minocycline hepatic metabolism
Excretion: Renal (doxycycline - hepatic)

Adverse effect: Chelate formation (Ca++ Mg++ Fe++) - teratogenic, dental staining in kids | GI disturbance | Photosensitivity | vestibulotoxicity

Question 5

Glycylcyclines

Answer 5

Tigecycline

Question 6

Tigecycline

Answer 6

Glycylcyclines
Minocycline derivative
Protein synthesis inhibitor S30 subunit - reversible inhibition (inhibits tRNA binding mRNA complex)
Bacteriostatic

Spectrum: MRSA, VRE, tetracycline resistant

Administration: IV
Distribution: large Vd, low plasma concentration
Excretion: Bille (long elimination half-life)

Adverse effect: similar to tetracyclines | Pancreatitis (may be fatal)