Zovirax (Acyclovir)
This is an anti-viral drug called Acyclovir that works by inhibiting viral DNA replication. The reason I thought this was so cool was because it exhibits high selectively toward virally-infected cells. How does it do that? You administer the drug in an inactive form called a prodrug, and once the prodrug is phosphorylated by kinase enzymes, it will be converted into its active form. The reason it's selective toward viral cells is because the viral kinase enzyme works 100x faster than our own kinase enzymes, such that only viral cells are activating the drug and not our own cells.Sinemet (L-DOPA/Carbidopa)
Parkinson's is a neurodegenerative disease in which the motor pathways of the central nervous system are lost and the patient experiences debilitating muscle tremors and is therefore unable to exercise fine muscle control. The loss of these cells results in an insufficient biosynthesis of dopamine, which is a neurotransmitter used in the action of these pathways.You could try treating this condition by directly adminstering dopamine, but this presents a couple key problems: dopamine cannot cross the blood-brain barrier (BBB) to get to the brain where it is needed, and administration in high doses causes severe nausea and vomiting. You could then try to administer L-DOPA, a precursor of dopamine that can cross the BBB. Unfortunately, DOPA decarboxylase, the enzyme that converts L-DOPA into dopamine, is present mainly in the peripheral tissues (eg, liver, heart, lungs, kidneys) and not in the brain, so L-DOPA is converted to dopamine before it can even get to the brain, and you still end up with the side effects.
What you can do is administer L-DOPA with a decarboxylase inhibitor known as Carbidopa. Carbidopa cannot cross the BBB, so it remains in the peripheral tissues and only inhibits those peripheral decarboxylase enzymes, leaving L-DOPA to be taken up into the neural tissues and restore motor function back to normal levels.
Pretty neat, huh?
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