What is the rationale for combining levodopa with carbidopa?

Correct Answer: B

Rationale: Levodopa treats Parkinson's by crossing the blood-brain barrier and converting to dopamine, but peripheral metabolism by dopa decarboxylase reduces its availability and causes side effects like nausea. Carbidopa, a peripheral dopa decarboxylase inhibitor, doesn't cross into the CNS, so it prevents levodopa breakdown outside the brain, increasing its CNS entry and efficacy. It doesn't stimulate dopamine receptors—levodopa's metabolite does that. Absorption isn't directly enhanced; bioavailability improves due to less peripheral loss. Peripheral dopamine production decreases with carbidopa, not increases, reducing side effects. COMT inhibition (e.g., entacapone) is a separate strategy. By blocking peripheral conversion, carbidopa ensures more levodopa reaches the brain, optimizing therapy and minimizing adverse effects.

Correct Answer: D

Rationale: Acute asthma and pneumonia in pregnancy require urgent care. IV crystalloids rehydrate, safe and necessary. High FiO2 (40%) supports oxygenation in asthma/pneumonia, appropriate. Nebulized salbutamol, a beta-agonist, relieves bronchospasm, standard and safe. IV hydrocortisone reduces inflammation, suitable. IV gentamicin, an aminoglycoside, treats pneumonia but is inappropriate due to cephalosporin cross-reactivity risk (angioedema history) and fetal ototoxicity concerns, making it unsafe here. Alternative antibiotics (e.g., macrolides) are preferred, prioritizing maternal and fetal safety.

Correct Answer: B

Rationale: Levodopa treats Parkinson's by crossing the blood-brain barrier and converting to dopamine, but peripheral metabolism by dopa decarboxylase reduces its availability and causes side effects like nausea. Carbidopa, a peripheral dopa decarboxylase inhibitor, doesn't cross into the CNS, so it prevents levodopa breakdown outside the brain, increasing its CNS entry and efficacy. It doesn't stimulate dopamine receptors—levodopa's metabolite does that. Absorption isn't directly enhanced; bioavailability improves due to less peripheral loss. Peripheral dopamine production decreases with carbidopa, not increases, reducing side effects. COMT inhibition (e.g., entacapone) is a separate strategy. By blocking peripheral conversion, carbidopa ensures more levodopa reaches the brain, optimizing therapy and minimizing adverse effects.

Correct Answer: C

Rationale: Seizure drugs (e.g., benzodiazepines like clonazepam) treat anxiety via GABA enhancement, calming overactivity, per pharmacology. Antitussives suppress cough, anticoagulants thin blood, and antibiotics fight infection-none target anxiety. Seizure drugs' anxiolytic use is established, fitting the need.

Correct Answer: C

Rationale: Naloxone is the drug used to reverse the effects of an opioid overdose. It is an opioid antagonist that rapidly binds to opioid receptors in the brain, displacing the opioid molecules. By blocking the receptor sites, naloxone can quickly reverse the effects of opioids, such as respiratory depression, sedation, and potential coma. Naloxone is a critical medication in opioid overdose situations as it can restore normal breathing and save a person's life. It is often available in the form of a nasal spray or injection for emergency use. It is essential for first responders, healthcare professionals, and individuals at risk of opioid overdose to have access to naloxone as part of overdose prevention and harm reduction strategies.