How to Verify Controlled Substance Quantities and Directions: A Practical Guide for Pharmacists

Getting the quantity and directions right on a controlled substance prescription isn’t just good practice-it’s the law. One wrong number, one unclear sig, and you could be looking at a DEA enforcement action, a license suspension, or worse, a patient harmed by a dosing error. In 2023, over 6,200 pharmacy and prescriber enforcement actions were tied to verification failures. Most of them? Simple mistakes in quantity or directions that could’ve been caught with a checklist and a second look.

What You Must Verify on Every Controlled Prescription

• Prescriber’s full name and address - No abbreviations. If it says "Dr. J. Smith, 123 Main St," that’s fine. If it says "Dr. Smith, 123 Main," you need to call and confirm.
• Date of issue - Schedule II prescriptions must be dated the day they’re presented. For Schedules III-V, the date can’t be more than six months old.
• Patient’s full name and address - Middle initials count. "J. Doe" and "John Doe" are different if the PDMP shows one but not the other.
• Drug name and strength - "Hydrocodone 5mg" isn’t the same as "Hydrocodone 7.5mg." Spell it out. Don’t assume.
• Dosage form - Tablet, capsule, liquid, patch? Each has different dosing implications, especially with opioids.
• Quantity prescribed - This is where most errors happen. The number must match the written word. "30 tablets" must equal "thirty (30)." If it doesn’t, pause. Call the prescriber.
• Directions for use (sig) - "Take one by mouth every 6 hours as needed for pain" is clear. "1 q6h PRN pain" is acceptable. "Take 1 tid"? That’s vague. Clarify it.

Don’t rely on memory. Print a checklist. Tape it to your monitor. Use it until it’s automatic.

Quantity Verification: The #1 Error Point

Here’s how to catch it:

1. Read the number out loud. "Thirty tablets."
2. Look at the number next to it. "30."
3. Do they match? If yes, move on. If no, stop. Don’t fill it.
4. If the prescription says "30" but the handwriting looks like "80," call the prescriber. Don’t guess.
5. Check the refill field. Is it marked "0"? If the quantity is 120 tablets and the refill says "3," that’s 480 tablets total. Is that clinically appropriate? If not, question it.

Handwritten prescriptions are the biggest risk. A 2023 Pharmacy Times survey found 68% of pharmacists struggle with illegible handwriting. Forty-one percent say they have to call a prescriber at least once a day just to clarify a quantity or direction. Don’t be embarrassed to call. It’s your job.

DEA Number Validation: The 3-Step Math Check

Here’s the official DEA method:

1. Take the first letter. It should be A, B, F, G, M, or X (for prescribers). If it’s not, the number is invalid.
2. The second letter must match the prescriber’s last name initial. If the prescriber is Dr. Patel, the second letter must be P. If it’s R, stop.
3. Now, the math:

Take the DEA number: AB1234567

• Add the 1st, 3rd, and 5th digits: 1 + 3 + 5 = 9
• Add the 2nd, 4th, and 6th digits: 2 + 4 + 6 = 12 → Multiply by 2 → 24
• Add both results: 9 + 24 = 33
• The last digit of that sum (3) must match the 7th digit of the DEA number.

33 → last digit is 3. DEA number’s 7th digit is 3. ✅ Valid.

The DEA says this catches 98.7% of fake DEA numbers. You don’t need an app. You need to know this. Practice it. Do it on every prescription.

PDMP Review: Your Real-Time Safety Net

Only 27 states require real-time data submission (under 5 minutes). The rest? Some take 24 hours. Some take a week. That gap? That’s where diversion happens.

Here’s how to use PDMP effectively:

• Check before you fill. Not after.
• Look for red flags: multiple prescribers, multiple pharmacies, overlapping prescriptions.
• Check the quantity and frequency. Is a patient getting 120 hydrocodone tablets every 10 days? That’s 360 per month. CDC guidelines say that’s excessive.
• Use PMP InterConnect. It’s the most reliable cross-state system. Pharmacists using it report a 37% reduction in verification time.

California pharmacists spend an average of 22 minutes per PDMP check. Tennessee? Nine minutes. Why? California’s system pulls in more data points. Don’t get frustrated-get efficient. Learn your state’s system. Bookmark it. Make it part of your workflow.

Opioid Conversion Factors: Don’t Guess, Calculate

Here are the key ones you need to know:

Example: A patient is prescribed 60mg of hydrocodone per day. That’s 60 morphine equivalents. Now they get a script for 20mg of hydromorphone per day. That’s 80 morphine equivalents. You just doubled their dose. That’s dangerous. You need to call the prescriber.

Keep a laminated copy of this table in your dispensing area. Or save it as a screenshot on your phone. Don’t rely on memory.

What the Experts Say: The 5-Point Verification Protocol

The American Society of Health-System Pharmacists (ASHP) recommends this 5-point protocol:

1. DEA number validation - Use the 3-step math check.
2. PDMP review - Check for red flags, overlapping scripts, high volumes.
3. Prescription integrity check - Look for tampering: microprinting, security paper, void indicators.
4. Prescriber verification - Call if anything looks off. Even if it’s after hours.
5. Clinical appropriateness - Use CDC conversion factors. Is this dose safe? Is this quantity reasonable?

Pharmacies using all five points have 4% diversion incidents. Those using one or none? 31%. The numbers don’t lie.

What’s Changing in 2025 and Beyond

That’s not science fiction. It’s coming. And it’s built on the DSCSA standards that became mandatory in November 2023. Pharmacies that haven’t upgraded their systems are already at risk of enforcement.

Meanwhile, AI tools are being piloted in 12 states to flag suspicious patterns-like a patient getting high-dose opioids from three different prescribers in three weeks. These aren’t replacing pharmacists. They’re giving you better data to make faster, safer decisions.

Final Checklist: Before You Hand Over the Bottle

• Did I verify the DEA number using the 3-step math?
• Did the written quantity match the numerical quantity?
• Did I check the PDMP today?
• Did I confirm the sig is clear and safe?
• Did I cross-reference opioid doses using CDC factors?
• Did I call the prescriber if anything felt off?

If you answered yes to all six, you’ve done your job. Not just legally. Ethically. Safely.

There’s no software that replaces your judgment. No app that catches a poorly written sig. No system that stops you from filling a 90-day supply of methadone when the patient has no history of chronic pain. That’s on you. And you’re the only one who can do it right.

Next Steps: Build Your Verification Routine

You’re not just filling prescriptions. You’re stopping diversion. You’re preventing overdose. You’re protecting your license. And you’re the last line of defense. Don’t let it slip.