Minocycline is a broad-spectrum tetracycline antibiotic, and has a broader spectrum than the other members of the group. It is a bacteriostatic antibiotic, classified as a long-acting type. Minocycline is the most lipid-soluble of the tetracycline-class antibiotics, giving it the greatest penetration into the prostate and brain, but also the greatest amount of central nervous system (CNS)-related side effects, such as vertigo. A common side effect is diarrhea. Uncommon side effects (with prolonged therapy) include skin discolouration and autoimmune disorders that are not seen with other drugs in the class. Minocycline is a relatively poor tetracycline-class antibiotic choice for urinary pathogens sensitive to this antibiotic class, as its solubility in water and levels in the urine are less than all other tetracyclines. Minocycline is metabolized by the liver and has poor urinary excretion.