Sketchy Pharm: Ganciclovir, Valganciclovir, Foscarnet, and Cidofovir

Question 1

All of the drugs in this sketch are used to treat _______________.

Answer 1

CMV, HSV, or VZV infections resistant to acyclovir and valacyclovir

Question 2

What is a common indication for use of ganciclovir?

Answer 2

CMV reactivation in an AIDS patient (with CD4s less than 50)

Think of the woman with the pizza – representing HIV retinitis –in the line for customers with 50 items or LESS.

Question 3

True or false: ganciclovir needs to be phosphorylated by viral kinases.

Answer 3

True! Like acyclovir, ganciclovir needs to be phosphorylated. However, it does so by a different enzyme: UL97 –an enzyme specific to CMV–accomplishes this.

(Think of the Mega-Lo employee putting the first P sticker on and then the kids, who are not Mega-Lo specific and represent cellular kinases, putting the second and third P’s on.)

Question 4

The defective GTP made by ganciclovir ultimately disrupts ______________.

Answer 4

viral DNA polymerase

Think of the conveyor belt that splits into two getting jammed by ganciclovir.

Question 5

What advantage does valganciclovir have?

Answer 5

Like valacyclovir, it has great bioavailability.

Think of the woman in the violet dress tossing the VALue snacks into her mouth.

Question 6

Ganciclovir and valganciclovir are often used for _______________.

Answer 6

prophylaxis in organ transplant patients

Think of the organs in the back of the scene.

Question 7

The biggest side effect of both ganciclovir and valganciclovir are ______________.

Answer 7

myelosuppression (particularly in patients receiving other myelotoxic agents like zidovudine)

(This is represented by the woman in the Z outfit next to the bone-shaped platter.)

Question 8

Which antiviral drugs do not require phosphorylation?

Answer 8

Foscarnet and cidofovir

(Think of the FaSt CAR NET kid slamming directly into the checkout and CyD the clerk directly turning off the cash register conveyor belt.)

Question 9

What side effects does foscarnet have?

Answer 9

Renal insufficiency (spilled barrel of kidney beans)
Hypocalcemia (spilled milk)
Hypomagnesemia (magnets knocked off cash register)
Hypokalemia (banana peels)

Question 10

The central adverse effect of cidofovir is ____________.

Answer 10

nephrotoxicity with resultant metabolic acidosis)

Think of CyD knocking over the kidney-shaped bottles.

Question 11

____________ must be administered with cidofovir to prevent negative side effects.

Answer 11

Probenecid (which prevents the renal excretion of cidofovir and thus limits its side effects)

(Think of CyD’s brother CID holding back the tumbling display of kidney-shaped bottles.)

Question 12

Probenecid prevents ________________.

Answer 12

many drugs from entering the kidney

“It’s like a PROBation officer preventing your kidney from doing drugs.”