Phenytoin correction (Sheiner–Tozer)

Phenytoin correction

Estimate an albumin-adjusted total-equivalent phenytoin concentration from observed total phenytoin and albumin, with an optional renal binding-factor change.

LIVE $0.005 USDC GET /api/calc/phenytoin_correction

Markdown: /docs/phenytoin-correction.md · Canonical: https://magentlab.com/docs/phenytoin-correction

Not a medical device. Not a diagnosis, dose, or listing recommendation.

What it computes

Estimate an albumin-adjusted total-equivalent phenytoin concentration from observed total phenytoin and albumin, with an optional renal binding-factor change.

When to use

When an agent needs the published Winter–Tozer arithmetic and must not invent a free phenytoin immunoassay result.

When not to use

Not a free phenytoin level, immunoassay substitute, or dosing order. Liponi, Winter, and Tozer 1984 discuss altered binding in renal failure; magent applies factor 0.1 only when renal_impairment=true.
Does not measure unbound phenytoin. Mauro 1989 (DICP) found poor agreement of these equations with measured free levels; treat the output as published arithmetic only.

Formula

corrected_phenytoin_mcg_ml = phenytoin_mcg_ml / ((binding_factor * albumin_g_dl) + 0.1); binding_factor 0.2, or 0.1 if renal_impairment

Citation

Title: Renal function and therapeutic concentrations of phenytoin
Authors: Liponi DF, Winter ME, Tozer TN
Source: Neurology. 1984;34(3):395-397
DOI: 10.1212/WNL.34.3.395

Worked example

Observed 8 µg/mL, albumin 2.0 g/dL, no renal impairment

Given: albumin_g_dl=2.0phenytoin_mcg_ml=8.0renal_impairment=false

denominator = 0.2 × 2.0 + 0.1 = 0.5
corrected = 8.0 / 0.5 = 16.0 µg/mL

Same labs with renal_impairment=true

Given: albumin_g_dl=2.0phenytoin_mcg_ml=8.0renal_impairment=true

denominator = 0.1 × 2.0 + 0.1 = 0.3
corrected = 8.0 / 0.3 = 26.7 µg/mL

Also searched as

Sheiner-Tozer phenytoin
Winter-Tozer
corrected phenytoin
phenytoin albumin correction
corrected total phenytoin

Try

Opens the live endpoint. Unpaid browser requests show the paywall; agents should send Accept: application/json.

/api/calc/phenytoin_correction?phenytoin_mcg_ml=8.0&albumin_g_dl=2.0&renal_impairment=false

Full URL: https://api.magentlab.com/api/calc/phenytoin_correction?phenytoin_mcg_ml=8.0&albumin_g_dl=2.0&renal_impairment=false

Call

Expect HTTP 402 until you retry with PAYMENT-SIGNATURE. Incomplete query params return HTTP 400 before any quote or charge.

curl -i -H "Accept: application/json" "https://api.magentlab.com/api/calc/phenytoin_correction?phenytoin_mcg_ml=8.0&albumin_g_dl=2.0&renal_impairment=false"

Parameters

Name	Type	Required	Description
`phenytoin_mcg_ml`	number	required	Observed total phenytoin in µg/mL (same as mg/L). Range 0.1-80.
`albumin_g_dl`	number	optional	Serum albumin in g/dL (1-6). Provide this or albumin_g_l.
`albumin_g_l`	number	optional	Serum albumin in g/L (10-60). Converted as g/dL = g/L / 10.
`renal_impairment`	boolean	required	true uses binding factor 0.1 (Liponi/Winter–Tozer end-stage renal adjustment). false uses 0.2. true or false.

Bulk (POST)

POST the same path with a JSON items array. The first item is the GET unit; each additional item is $0.002. Invalid items return HTTP 400 before settlement.

POST /api/calc/phenytoin_correction Max 25 unit_amount + extra_item_amount * (n - 1) extra $0.002 PREVIEW

1 to 25 items. Each item uses the same keys as the GET query parameters.
POST of 1 item costs the same as GET. Lists longer than 25: chunk into multiple POSTs. Extra items still execute; do not pad dummy rows.
The first invalid item fails the whole request (index in the 400 JSON). You are not charged.
HTTP 200 is {count, path, items}. Each items[i] is the GET 200 body for that row.
Catalog misses (empty matches, found=false) stay paid 200s inside that slot.
x402 resource URL is this path plus n and body_sha256. Browsers that prefer text/html get the same paywall as GET; Pay retries POST with the same items.

Example request (fixture)

{
  "items": [
    {
      "albumin_g_dl": "2.0",
      "phenytoin_mcg_ml": "8.0",
      "renal_impairment": "false"
    },
    {
      "albumin_g_dl": "2.0",
      "phenytoin_mcg_ml": "8.0",
      "renal_impairment": "false"
    }
  ]
}

Open bulk paywall →

Opens a two-item fixture on the API host. Unpaid browsers get the same MetaMask paywall as GET; Pay retries POST with those items.

Example 200 (fixture)

{
  "count": 2,
  "path": "/api/calc/phenytoin_correction",
  "items": [
    {
      "disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.",
      "citation": {
        "authors": "Liponi DF, Winter ME, Tozer TN",
        "doi": "10.1212/WNL.34.3.395",
        "id": "liponi-1984",
        "source": "Neurology. 1984;34(3):395-397",
        "title": "Renal function and therapeutic concentrations of phenytoin"
      },
      "formula": "sheiner_tozer",
      "formula_expression": "corrected_phenytoin_mcg_ml = phenytoin_mcg_ml / ((binding_factor * albumin_g_dl) + 0.1); binding_factor 0.2, or 0.1 if renal_impairment",
      "albumin_g_dl": 2.0,
      "binding_factor": 0.2,
      "corrected_phenytoin_mcg_ml": 16.0,
      "phenytoin_mcg_ml": 8.0,
      "renal_impairment": false
    },
    {
      "disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.",
      "citation": {
        "authors": "Liponi DF, Winter ME, Tozer TN",
        "doi": "10.1212/WNL.34.3.395",
        "id": "liponi-1984",
        "source": "Neurology. 1984;34(3):395-397",
        "title": "Renal function and therapeutic concentrations of phenytoin"
      },
      "formula": "sheiner_tozer",
      "formula_expression": "corrected_phenytoin_mcg_ml = phenytoin_mcg_ml / ((binding_factor * albumin_g_dl) + 0.1); binding_factor 0.2, or 0.1 if renal_impairment",
      "albumin_g_dl": 2.0,
      "binding_factor": 0.2,
      "corrected_phenytoin_mcg_ml": 16.0,
      "phenytoin_mcg_ml": 8.0,
      "renal_impairment": false
    }
  ]
}

Response

Field	Type	Description
`formula`	string	sheiner_tozer
`formula_expression`	string	Exact expression used
`phenytoin_mcg_ml`	number	Observed total phenytoin used
`albumin_g_dl`	number	Normalized albumin in g/dL
`renal_impairment`	boolean	true when the renal binding factor 0.1 was used
`binding_factor`	number	0.2 normally, 0.1 when renal_impairment is true
`corrected_phenytoin_mcg_ml`	number	Albumin-adjusted total-equivalent phenytoin in µg/mL, 1 decimal
`citation`	object	Liponi, Winter, and Tozer 1984 citation
`disclaimer`	string	Not-a-device notice

Example JSON

Machine form of the same example. Frozen fixture. Not a live lookup.

{
  "disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.",
  "citation": {
    "authors": "Liponi DF, Winter ME, Tozer TN",
    "doi": "10.1212/WNL.34.3.395",
    "id": "liponi-1984",
    "source": "Neurology. 1984;34(3):395-397",
    "title": "Renal function and therapeutic concentrations of phenytoin"
  },
  "formula": "sheiner_tozer",
  "formula_expression": "corrected_phenytoin_mcg_ml = phenytoin_mcg_ml / ((binding_factor * albumin_g_dl) + 0.1); binding_factor 0.2, or 0.1 if renal_impairment",
  "albumin_g_dl": 2.0,
  "binding_factor": 0.2,
  "corrected_phenytoin_mcg_ml": 16.0,
  "phenytoin_mcg_ml": 8.0,
  "renal_impairment": false
}

Client errors (HTTP 400)

Invalid params return 400 without charge. Shared HTTP 402 and 503 meanings: Payments.

HTTP	Code	When
400	`invalid_phenytoin`	phenytoin_mcg_ml (same as mg/L) must be a number from 0.1 to 80. Returned before settlement; you are not charged.
400	`invalid_albumin`	albumin_g_dl (1-6) or albumin_g_l (10-60) is required Returned before settlement; you are not charged.
400	`invalid_flag`	boolean clinical flags must be true or false Returned before settlement; you are not charged.
400	`invalid_items`	POST body must be a JSON object with only an items array Returned before settlement; you are not charged.
400	`invalid_item_count`	items must be an array of 1 to 25 objects Returned before settlement; you are not charged.
400	`invalid_item`	each items entry must be a JSON object Returned before settlement; you are not charged.

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Payment

Unpaid requests return HTTP 402 even if query parameters or POST items are missing or invalid, so CDP and agents can index the path. After a PAYMENT-SIGNATURE, invalid params return HTTP 400 JSON before settlement. magent does not charge. Fix the params, then request a new 402 quote for that complete URL. Catalog misses (empty matches, found=false) are valid paid 200s. Unpaid valid requests return HTTP 402 with a base64 PAYMENT-REQUIRED header. HTTP 503 is not a new quote: retry the same PAYMENT-SIGNATURE. Full handshake and shared payment errors: Payments. Stdio MCP: /docs/mcp.

Guarantees

HTTP 402 is unpaid, including a missing query. After PAYMENT-SIGNATURE, invalid parameters return HTTP 400 before settlement. You are not charged.
exact: settlement finishes before the tool (paymentFlow upfront). batch-settlement: verify/deposit before the tool; chargedCumulativeAmount commits after HTTP 2xx. Uncertain or failed settlement fails closed (HTTP 503). Retry the same PAYMENT-SIGNATURE.
HTTP 402 is unpaid only. Do not sign a second authorization because of a 503.
Execution is timeout-bounded and concurrency-capped.
Calculator inputs are stored encrypted for allowlisted operators (Magent Console). They are not in public logs, SSH lookups, catalog, or rollups. Request logs store path without query.