Pharmacy and Pharmacology: free VTNE practice questions

Pimobendan is an inodilator, meaning it acts as both a positive inotrope and a vasodilator. Its positive inotropic mechanism is unique: unlike catecholamines (dobutamine) or digoxin, pimobendan does not increase the release of calcium from intracellular storage sites. Instead, it increases the sensitivity of the contractile elements (troponin C) to calcium, enhancing calcium binding and producing a more effective contraction without raising intracellular calcium concentration. Digoxin, by contrast, inhibits the sodium-potassium-ATPase pump, causing intracellular sodium to accumulate, which displaces calcium from its storage sites and increases calcium availability for contraction. This elevated intracellular calcium is thought to contribute to digoxin's arrhythmogenic risk and reduced long-term survival compared to pimobendan.

Option A reverses the mechanisms.

Option C misattributes digoxin's mechanism to pimobendan and invents a beta-1 mechanism for digoxin.

Option D is false because pimobendan has both inotropic and vasodilator effects.

Convert both percentages into the same units before touching the equation - that single step is where most of these problems are won or lost. A percentage solution is grams per 100 mL, so 50% dextrose is 50 g per 100 mL, which is 500 mg/mL, and 2.5% dextrose is 2.5 g per 100 mL, which is 25 mg/mL. Now C1 = 500 mg/mL, C2 = 25 mg/mL and V2 = 500 mL. Solving (500 mg/mL)(V1) = (25 mg/mL)(500 mL) gives V1 = 12,500 / 500 = 25 mL of the 50% stock. Each wrong option is a specific and recognizable slip. 12.5 mL is the mass of dextrose the bag actually needs - 2.5 g per 100 mL times five gives 12.5 grams - reported as though grams of drug and milliliters of stock were the same number; they are not, because the stock solution is only half drug by weight. 250 mL comes from converting the 2.5% correctly to 25 mg/mL but leaving the 50% stock as 50 mg/mL, a tenfold error in one term only. 50 mL is the right method applied to a 1000 mL bag instead of a 500 mL bag. One practical point beyond the arithmetic: to end up with an exact 2.5% solution you would remove 25 mL of fluid from the bag before adding the 25 mL of stock. Many practices skip that step as long as the volume added is under 10% of the bag volume, so find out what the veterinarian you work with prefers.

The penicillins are usually recognizable by the -cillin ending on the generic name, and they are also called beta-lactam antibiotics after a ring-like structure in their chemical makeup. The cephalosporins are the other major group built on that same beta-lactam ring. Within the penicillins, the drugs used in veterinary medicine fall into four named subgroups, and knowing which subgroup a drug sits in is what this order is really asking for. The natural penicillin is penicillin G. The broad-spectrum aminopenicillins are ampicillin and amoxicillin. The penicillinase-resistant, or beta-lactamase-resistant, penicillins - named for resisting that enzyme - are cloxacillin, dicloxacillin, oxacillin, and methicillin, so oxacillin is the drug being asked for. The extended-spectrum penicillins are ticarcillin, carbenicillin, and piperacillin. Amoxicillin is the tempting wrong answer because broad-spectrum sounds like the stronger, more capable choice, but breadth of spectrum and resistance to an enzyme are two different labels: an aminopenicillin covers a wider range of organisms without belonging to the enzyme-resistant group. Ticarcillin fails for the same reason one step further out - extended-spectrum is again a statement about coverage, not about the enzyme. Penicillin G is the original natural penicillin, the plain drug the veterinarian specifically ruled out.