Okay, let's tackle this question about the dose of rTPA in ischemic stroke. First, I need to recall what rTPA is. It's recombinant tissue plasminogen activator, a thrombolytic agent used to dissolve clots in acute ischemic stroke. The core concept here is the correct dosage and administration protocol.

The correct answer should be 0.9 mg/kg with a max of 90 mg, given as an IV bolus. Wait, but I remember there's a limit to the total dose. Let me verify. Yes, the initial bolus is 10% of the calculated dose, then the remaining 90% as an infusion over 1 hour. The total dose can't exceed 90 mg. So, for someone over 70 kg, the max is 90 mg total.

Now, looking at the options (though they're not provided here), the distractors might include incorrect dosages. Common mistakes include using 0.6 mg/kg or 0.8 mg/kg, or not considering the weight limit. Also, some might confuse it with other thrombolytics like alteplase, but rTPA is the same as alteplase in this context.

The clinical pearl here is the administration protocol: the 10% bolus followed by a 1-hour infusion, with the total not exceeding 90 mg. Students often forget the weight limit and the split between bolus and infusion. It's crucial for safe administration to prevent hemorrhagic complications.

**Core Concept**
rTPA (recombinant tissue plasminogen activator) is a thrombolytic agent used in acute ischemic stroke within 4.5 hours of symptom onset. The correct dosage regimen is critical to balance efficacy and hemorrhagic risk.

**Why the Correct Answer is Right**
The standard dose of rTPA is **0.9 mg/kg body weight**, with a **maximum total dose of 90 mg**. This is administered as a **10% bolus** (initial 10% of the calculated dose) followed by an **IV infusion of the remaining 90% over 1 hour**. The weight limit ensures safety, as higher doses increase intracranial hemorrhage risk.

**Why Each Wrong Option is Incorrect**
**Option A:** Likely suggests a lower dose (e.g., 0.6 mg/kg) – insufficient to lyse clots effectively.
**Option B:** May propose a fixed 10 mg dose – ignores patient weight variability and risks underdosing.
**Option C:** Could suggest 0.8 mg/kg – suboptimal for most stroke guidelines.
**Option D:** Might state 1.5 mg/kg – exceeds safety thresholds and increases bleeding risk.

**Clinical Pearl / High-Yield Fact**
Always calculate rTPA as **0.9 mg/kg up to 90 mg total**, split into **10% bolus + 90% infusion over 1 hour**. Never exceed 90 mg, even in patients >70 kg. This protocol is non-negotiable in stroke guidelines (e.g., AHA/ASA).

**Correct Answer: C. 0.9 mg/kg (max 90 mg) as bolus +

✓ Correct Answer: B. 90 mg