Comparison

Preop Eval vs Opioids Dosage Conversion

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

Preop Eval

This app provides guidance for evaluating and preparing adult patients for non-cardiac surgery. It includes algorithms and resources on medication management, cardiac event timing, and preoperative testing, serving as both a reference and a teaching tool for medical professionals.

Highlights
  • Cardiac evaluation algorithm
  • Medication guidance (starting/stopping)
  • Surgery timing after cardiac events
  • Preoperative testing recommendations
  • Review for students and residents
  • Perioperative insulin management
Features
Read full description

Preop Eval organizes and presents much of the guidance that one needs in order to evaluate and prepare adult patients for non-cardiac surgery. It is based upon the guidelines on this topic from the American College of Cardiology, the European Society of Anaesthesiology, the American Society of Anesthesiologists, the Institute for Clinical Systems Improvement, the American College of Chest Physicians, and more (full references in the app). The app contains 1 algorithm and 3 resources: the cardiac evaluation algorithm, guidance on starting and stopping key medications in the perioperative period, guidance on timing of surgery after cardiac events, and guidance on preoperative testing. It also contains a review of preoperative evaluation mainly for students and residents. The app addresses such common questions as: - who needs bloodwork before surgery? - who needs an EKG or a CXR? - how do I handle patients on warfarin, clopidogrel, and DOAC's? - which patients need adjustment of perioperative insulin and diabetic meds, and how? - which active cardiac conditions preclude surgery? - how long after MI or stent should a patient wait before surgery? - are there adjustments to make on psych meds, rheumatologic meds, ACE's and ARB's? This app is written and intended for practicing physicians like internists, family physicians, and hospitalists; for resident physician trainees; and for medical students. In addition to being a reference, the algorithm is written to be a teaching tool by not just delivering an answer, but instead walking a physician through the evaluation process so that one learns that process along the way. As an educator and clinician, I am interested in feedback and I would be grateful for guidance on improving the tool.

About

Opioids Dosage Conversion

This app is a calculator for trained medical professionals to convert opioid analgesic dosages. It supports various common opioids and administration routes, offering features like breakthrough dosing and cross-tolerance calculations.

Highlights
  • Opioid dosage conversion
  • Multiple drug support
  • Multiple route support
  • Breakthrough dosing calculator
  • Incomplete cross tolerance option
  • Instructional details
Features
Read full description

Opioids by Chris Marcellino MD and Norris Vivatrat MD is an opioid analgesic dosage conversion calculator for use by trained medical professionals. The application supports conversion to and from opioids commonly prescribed and used in U.S. hospitals orally, parenterally, or transdermally, including morphine, codeine, hydromorphone, hydrocodone, fentanyl, methadone, oxycodone and oxymorphone. The application is intended to help and instruct in the process of conversion of opioid regimens. • Native support for iPhone, iPad and iPod touch • Multiple route support • Multiple drug support • Incomplete cross tolerance option • Breakthrough dosing calculator • Provides instructional details about each calculation • Saves last calculation on exit • Supports landscape and portrait modes • Reference guide By Professor EBM, the Internal Medicine Residency Teaching Resource for Evidence-Based Medicine: http://www.professorebm.com/, a resource of the Santa Clara Valley Medical Center. While effort has been made to ensure that calculations are accurate and that conversion factors are in accordance with current accepted medical practices, use of this application is entirely at your own risk. This application should only be used by trained medical professionals and all results should be double checked by hand. Use of the app requires acceptance of the terms of use that are included with the application. Please send support requests and feedback using the link in the About tab of the app, though as a free academic tool we only have limited resources to address new feature requests. Opioid equipotency data is taken from CAPC conversion values except where noted (see the reference tab in the app.) CAPC values are as published in the Center to Advance Palliative Care Prescribing Opioids: A Reference Guide curriculum, which are adapted from McPherson ML. Demystifying Opioid Conversion Calculations: A Guide for Effective Dosing, 2nd ed. American Society of Health-System Pharmacists, Bethesda, Maryland, 2018. EPEC values are as published in EPEC-O Participants Handbook, 2005. Chris Marcellino, MD — Mayo Clinic Norris Vivatrat, MD — UCSD Medical Center Special thanks to Dr. Tom Mouser (EveryStep, Des Moines, IA) and Dr. David Rand (UVM Medical Center).

Screenshots

Preop Eval4 screens
Opioids Dosage Conversion4 screens

Verdict

The call

The clearest difference is rating: Preop Eval at 5.0 against Opioids Dosage Conversion's 4.3. Opioids Dosage Conversion's advantage is ratings volume (19 vs 2) and review sentiment (78% vs 67%). On price, update cadence, ads and in-app purchases there is nothing between them.

Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS

CostPrice · In-app purchases · Ads · Monetization

Both are free to download. Neither carries in-app purchases, so what you see is what you pay.

ReceptionRating · Positive reviews · Number of ratings

Preop Eval holds the better App Store score, 5.0 against 4.3. That said, the two scores are not equally well evidenced: Opioids Dosage Conversion has 19 ratings behind it against 2, so its average is the more settled of the two. Written reviews complicate that: 67% of Preop Eval's written reviews are positive against 78% of Opioids Dosage Conversion's, so the app with the better star average is not the one people write more warmly about.

UpkeepUpdate frequency

Preop Eval ships an update every 6 months, Opioids Dosage Conversion every 4 months. The most recent releases landed on November 6, 2026 and November 1, 2026 respectively.

Scorecard4 real differences · 6 level
Preop Eval versus Opioids Dosage Conversion: the parameters behind the verdict, then further details
ParameterPreop EvalOpioids Dosage Conversion
PriceFreeFree
Rating5.0 (2 ratings) — better4.3 (19 ratings)
Positive reviews66.7% of reviews77.8% of reviews — better
Number of ratings219 — better
Update frequencyEvery 6 monthsEvery 4 months — better
AdsNoNo
In-app purchasesNoNo
MonetizationFreeFree
DevicesiPhoneiPhone, iPad, iPod — better
Requires iOS16.615.6 — better
Further details — not scored
Size15 MB2 MB
Age rating17+17+
DeveloperUnited Health Services, Inc.Chris Marcellino MD LLC

Customer experience

Preop Eval

All ratings2 ratings
Positive100.0%
Neutral0.0%
Negative0.0%
Written reviews12 reviews
Positive66.7%
Neutral8.3%
Negative25.0%

Opioids Dosage Conversion

All ratings17 ratings
Positive82.4%
Neutral5.9%
Negative11.8%
Written reviews45 reviews
Positive77.8%
Neutral13.3%
Negative8.9%

In-app purchases

None

Preop Eval

No in-app purchases

None

Opioids Dosage Conversion

No in-app purchases

Questions

Is Preop Eval free?
Preop Eval is free to download, with no in-app purchases.
Is Opioids Dosage Conversion free?
Opioids Dosage Conversion is free to download, with no in-app purchases.
Which has better reviews, Preop Eval or Opioids Dosage Conversion?
Preop Eval is rated higher. Preop Eval averages 5.0 out of 5 from 2 ratings, while Opioids Dosage Conversion averages 4.3 from 19 ratings.
Do Preop Eval or Opioids Dosage Conversion have ads?
Neither Preop Eval nor Opioids Dosage Conversion shows ads.
Which is updated more often, Preop Eval or Opioids Dosage Conversion?
Preop Eval ships an update every 6 months, and Opioids Dosage Conversion every 4 months. Most recently, Preop Eval was updated on November 6, 2026 and Opioids Dosage Conversion on November 1, 2026.

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