DoseRx

The problem

A doctor works out a weight-based dose for every patient. Multiply the dose per kilogram by the weight, divide by the number of doses, convert to millilitres, and check against the maximum. For children, the dose depends on weight and a mistake can do harm. The usual tools are paper references, a phone calculator or a spreadsheet. None of them is quick to use with one hand at the bedside.

DoseRx is built for one practising doctor who works on a phone at the bedside and on a desktop. It needs no accounts and no server.

What I built

The maths lives in one place, apart from the screens

I kept the dose calculation separate from the interface. It takes typed inputs, checks them, applies the dose caps and returns either a result or an error. A screen has to check which one it got before it shows a number. So a failed calculation can never appear as a dose, and a broken value never reaches the doctor. The same engine serves every calculator and is tested on its own.

Doses snap to what an Indonesian pharmacy sells

After calculating a dose, the app suggests the tablet fraction or syrup volume to give, using preparations sold in Indonesian pharmacies. Tablets snap to fractions a person can cut: ¼, ½, ¾, 1, 1½ and 2. The app shows the dose actually delivered next to the target, so the doctor sees any rounding. The Puyer tab does the same for compounded powders. It calculates each drug in a batch and prints a combined recipe card with tablet counts and signa.

Every drug can carry more than one dose

The catalog first modelled one dose per drug. That broke once diazepam needed one dose by IV for a seizure and a different dose by mouth for anxiety, and once adult dosing sat next to a drug's paediatric numbers. I split "drug" from "dose": each drug now holds one or more regimens, one per route, indication and population, while every existing dose stayed exactly as it was, so past calculations still compute from the same numbers. The catalog has grown alongside this, from the original 8 seed drugs to 127, now organised into 9 clinical groups instead of the earlier 17 flat categories.

Unverified drugs wait behind a review gate

New drugs, routes and doses arrive faster than I can personally re-verify each one against a source. I built a separate review state instead. A new entry starts as a draft with its source cited and stays invisible outside review mode, marked as unverified everywhere it would otherwise show. Only I can move it into the reviewed catalog. As of the most recent commit, the draft list is empty, meaning the current drug list has been through that check.

Navigation follows the clinical task at hand

The app began with four tabs: Preset, Custom, Puyer, Infus. That matched the four calculation engines, not how a doctor actually thinks at the bedside, closer to what an emergency needs than which calculator to open. I replaced the tabs with task-based destinations instead: Obat, Darurat, Puyer, Cairan and Riwayat, with one shared patient-weight bar carried across all of them.

Result

DoseRx is live on GitHub Pages and installs to a phone's home screen, working offline once loaded. Recent and starred drugs sit at the top of the picker, keeping the 127-drug catalog fast to search with one hand, and every calculation is saved in the browser with an optional note. The original spec had 8 drugs and three panels, built over about three and a half weeks in June and July 2026. I kept returning to it through September for a second pass that replaced the tab structure with task-based navigation, added the review workflow for unverified drugs, and grew the catalog to its current size. The app states plainly that it is a calculation aid, not clinical decision support.