A 67 year old man presents with complaints of tremors, trouble walking and masked face, Parkinson disease is suspected. Levodopa is prescribed along with a compound to lower required dose of levodopa and to achieve an effective brain dopamine concentration. Which of the following is that most likely compound?
A) Pergolide
B) Selegiline
C) Carbidopa
D) Entacapone
The correct answer is C) Carbidopa
Why?
Levodopa is a precursor to dopamine. On its own, most Levodopa is converted into dopamine by an enzyme called DOPA decarboxylase before it ever reaches the brain. This is problematic because:
→Dopamine cannot cross the blood-brain barrier (BBB); only its precursor (Levodopa) can.
→High levels of dopamine in the bloodstream cause significant side effects like nausea and heart palpitations.
Carbidopa is a DOPA decarboxylase inhibitor that cannot cross the blood-brain barrier. By blocking the conversion of Levodopa in the "periphery" (the rest of the body), it ensures more Levodopa remains available to enter the brain, where it can then be converted into the dopamine the patient needs. Thus Carbidopa:
↪Reduces the required dose of levodopa.
↪Decreases peripheral side effects (nausea, vomiting, hypotension)
| Drug | Mechanism | Role in Therapy |
| Pergolide | Dopamine Agonist | Directly stimulates dopamine receptors; it doesn't "lower the required dose" of Levodopa in the same way. |
| Selegiline | MAO-B Inhibitor | Prevents the breakdown of dopamine inside the brain. |
| Entacapone | COMT Inhibitor | Often used with Levodopa/Carbidopa to prevent Levodopa breakdown, but Carbidopa is the primary agent used to initially "achieve effective concentration" and reduce the base dose. |
Carbidopa is the "bodyguard" that gets Levodopa safely to the brain's door.
The prescription of a patient shows Xalatan drops 1 drop o.n.m. 1 bottle which of the following is the most likely condition?
A) Cataract
B) Glaucoma
C) Blepharitis
D) Conjunctivitis
The most likely condition is B) Glaucoma.
Xalatan is the brand name for Latanoprost, a medication specifically designed to lower intraocular pressure (IOP).
Why Xalatan is used for Glaucoma
Latanoprost belongs to a class of drugs called prostaglandin analogs. It works by increasing the outflow of aqueous humor (the fluid inside the eye) through the uveoscleral pathway. By reducing the pressure inside the eye, it prevents damage to the optic nerve, which is the primary concern in glaucoma.
Understanding the Prescription
The shorthand used in the prescription provides a big clue:
Xalatan: Specifically indicated for open-angle glaucoma or ocular hypertension.
1 drop o.n.m.: This stands for omni nocte mane (or more commonly interpreted in modern clinical practice as once nightly). Prostaglandins like Xalatan are most effective when administered once in the evening.
Why the other options are unlikely:
❌Cataract: This is a clouding of the lens. The only effective treatment is surgical removal; there are no eye drops that can "clear" a cataract.
❌Blepharitis: This is inflammation of the eyelids, usually treated with warm compresses, lid hygiene, or topical antibiotics/steroids.
❌Conjunctivitis: Commonly known as "pink eye," this is usually treated with antibiotic, antiviral, or antihistamine drops depending on whether the cause is bacterial, viral, or allergic.
Fun Fact/Warning: One unique side effect of Xalatan that patients often notice is that it can permanently darken the iris color (making light eyes turn brown) and cause eyelashes to grow longer and thicker!
Which of the following products is an oleaginous ointment base?
1-Soft paraffin (Petroleum)
2-Polysorb
3-Aquabase
4-Anhydrous lanolin
Based on the criteria that an oleaginous base consists primarily of hydrocarbons (oils and fats) and is strictly anhydrous and non-emulsifying, the correct answer is 1-Soft paraffin (Petroleum).
Oleaginous (hydrocarbon) ointment bases are made of oils and fats, are greasy, occlusive, and do not absorb water.
The other three options belong to a different category called Absorption Bases. While they contain oily substances, they also contain emulsifiers, which allows them to "absorb" water.
| Property | Oleaginous Base (Soft Paraffin) | Absorption Base (Lanolin, Polysorb) |
| Water Content | Anhydrous (None) | Anhydrous (but can absorb water) |
| Washability | Non-washable | Non-washable |
| Occlusiveness | Very High | High |
| Emulsifier | None | Present |
Which of the following is the benefit from adding a conjugate of polyethylene glycol (PEG) in some medications like Peg-interferon?
A) to extend the half-life of medications
B) to extend the shelf-life of medications
C) to enhance the effect of the medications
D) to enhance the elimination of the medications
The correct answer is A) To extend the half-life of medications.
This process is known as PEGylation. It involves the covalent attachment of polyethylene glycol (PEG) polymer chains to another molecule, typically a drug or therapeutic protein like interferon.
How PEGylation Works
Adding a PEG conjugate transforms the medication in several key ways to keep it in the body longer:
☛Increased Size: The PEG chain is bulky and highly hydrated. This increases the overall hydrodynamic size of the drug molecule, making it too large to be filtered out easily by the kidneys (reduced renal clearance).
☛Steric Hindrance: The "PEG mask" physically shields the drug from proteolytic enzymes (which try to break it down) and prevents it from being recognized by the immune system as a foreign invader.
☛Reduced Dosing Frequency: Because the drug stays in the system much longer, a patient who might have needed daily injections of standard interferon may only need one injection per week of Peg-interferon.
Evaluating Other Options
❌B) Shelf-life: While PEG can occasionally help with stability, "shelf-life" usually refers to the expiration date in the bottle. PEGylation is primarily focused on the drug's performance inside the body.
❌C) Enhance effect: PEGylation actually often decreases the initial binding affinity (potency) of the drug because the bulky chains get in the way. However, the drug is more effective overall because it remains at a steady therapeutic level for a longer duration.
❌D) Enhance elimination: This is the opposite of what PEG does. The goal is to slow down elimination to maintain blood concentrations.
PEG acts like a "protective cloak" that keeps the medication from being chewed up by enzymes or flushed out by the kidneys.
The pharmacist received a prescription to extemporaneously prepare moxifloxacin oral suspension from the 400mg tablet in a concentration of 20 mg/ml with total volume of 60mL.
Which of the following is the number of tablets of moxifloxacin 400 mg needed to prepare the above prescription?
A) 2
B) 3
C) 4
D) 6
The correct answer is B) 3
To determine the number of tablets required, you can follow these calculation steps:
1. Calculate the total amount of drug needed
First, find the total milligrams (mg) of moxifloxacin required for the entire volume of the suspension:
2. Calculate the number of tablets
Next, divide the total amount needed by the strength of a single tablet:
Summary: You will need 3 tablets of moxifloxacin 400 mg to create 60 mL of a 20 mg/mL suspension.
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