PharmGKB Clinical Pharmacogenomics Database

Overview

PharmGKB is the leading pharmacogenomics knowledge resource, curating how genetic variation affects drug response. It integrates CPIC (Clinical Pharmacogenomics Implementation Consortium) and DPWG (Dutch Pharmacogenomics Working Group) dosing guidelines, clinical annotations of variant-drug associations, gene-drug pathways, and literature evidence. The REST API provides free programmatic access without authentication to 24,000+ variant-drug annotations, 800+ clinical annotations, and 300+ CPIC guidelines.

When to Use

• Retrieving CPIC/DPWG clinical dosing guidelines for a specific gene-drug pair (e.g., CYP2C19-clopidogrel)
• Looking up all pharmacogenomic variants associated with a drug's response or toxicity
• Finding all drugs whose dosing is affected by variants in a pharmacogene (e.g., CYP2D6, DPYD)
• Retrieving PharmGKB clinical annotation levels (1A, 1B, 2A, 2B, 3, 4) for a variant-drug association
• Building precision medicine dosing workflows that incorporate genotype-guided prescribing
• Fetching pharmacogenomic pathways (e.g., warfarin pharmacokinetics/pharmacodynamics) with gene roles
• For cancer somatic pharmacogenomics use

  cosmic-database

  or

  opentargets-database

Prerequisites

• Python packages:

  requests

  ,

  pandas

• Data requirements: gene symbols (HGNC), drug names, dbSNP rsIDs, or PharmGKB IDs
• Environment: internet connection; no authentication required
• Rate limits: no stated limit; use reasonable delays (~0.2s) for bulk queries

pip install requests pandas

Quick Start

import requests

BASE = "https://api.pharmgkb.org/v1"

# Search for clinical annotations for CYP2D6
r = requests.get(f"{BASE}/clinicalAnnotation",
                 params={"gene": "CYP2D6", "view": "base"})
r.raise_for_status()
data = r.json()
print(f"CYP2D6 clinical annotations: {data['count']}")
for ann in data["data"][:3]:
    print(f"  Level {ann.get('evidenceLevel')}: {ann.get('drug', {}).get('name')} | {ann.get('phenotype')}")

Core API

Query 1: Clinical Annotations by Gene or Drug

Retrieve variant-drug clinical annotations with evidence levels.

import requests, pandas as pd

BASE = "https://api.pharmgkb.org/v1"

def get_clinical_annotations(gene=None, drug=None, level=None):
    params = {"view": "base"}
    if gene:
        params["gene"] = gene
    if drug:
        params["drug"] = drug
    if level:
        params["level"] = level
    r = requests.get(f"{BASE}/clinicalAnnotation", params=params)
    r.raise_for_status()
    return r.json()

# All 1A annotations (highest evidence) for warfarin
data = get_clinical_annotations(drug="warfarin", level="1A")
print(f"Warfarin 1A annotations: {data['count']}")

rows = []
for ann in data["data"][:10]:
    rows.append({
        "gene": ann.get("gene", {}).get("symbol"),
        "variant": ann.get("variant", {}).get("name"),
        "drug": ann.get("drug", {}).get("name"),
        "level": ann.get("evidenceLevel"),
        "phenotype": ann.get("phenotype"),
        "significance": ann.get("clinicalSignificance"),
    })
df = pd.DataFrame(rows)
print(df.to_string(index=False))

# By rsID
def get_annotations_by_variant(rsid):
    r = requests.get(f"{BASE}/clinicalAnnotation",
                     params={"variant": rsid, "view": "base"})
    r.raise_for_status()
    return r.json()

data_rs = get_annotations_by_variant("rs4149056")  # SLCO1B1 variant for statin myopathy
print(f"\nrs4149056 annotations: {data_rs['count']}")
for ann in data_rs["data"][:5]:
    print(f"  Drug: {ann.get('drug', {}).get('name'):20s} Level: {ann.get('evidenceLevel')}")

Query 2: CPIC/DPWG Dosing Guidelines

Retrieve clinical dosing guideline recommendations for gene-drug pairs.

import requests, pandas as pd

BASE = "https://api.pharmgkb.org/v1"

def get_guidelines(gene=None, drug=None):
    params = {"view": "base"}
    if gene:
        params["gene"] = gene
    if drug:
        params["drug"] = drug
    r = requests.get(f"{BASE}/guideline", params=params)
    r.raise_for_status()
    return r.json()

# Guidelines for CYP2C19 gene (clopidogrel, SSRIs, PPIs)
data = get_guidelines(gene="CYP2C19")
print(f"CYP2C19 dosing guidelines: {data['count']}")

for gl in data["data"][:5]:
    source = gl.get("source", "")
    name = gl.get("name", "")
    url = gl.get("url", "")
    print(f"\n  [{source}] {name}")
    print(f"  URL: {url}")

# Guidelines for a specific drug
data_drug = get_guidelines(drug="clopidogrel")
print(f"\nClopidogrel guidelines: {data_drug['count']}")
for gl in data_drug["data"]:
    print(f"  {gl.get('source')}: {gl.get('name')}")

Query 3: Gene Information and Related Drugs

Retrieve pharmacogene information and all associated drugs.

import requests, pandas as pd

BASE = "https://api.pharmgkb.org/v1"

def get_gene_info(gene_symbol):
    r = requests.get(f"{BASE}/gene", params={"symbol": gene_symbol, "view": "max"})
    r.raise_for_status()
    return r.json()

data = get_gene_info("CYP2D6")
gene = data["data"][0] if data["data"] else {}

print(f"Gene: {gene.get('symbol')}")
print(f"PharmGKB ID: {gene.get('id')}")
print(f"Name: {gene.get('name')}")
print(f"CPIC gene: {gene.get('cpicGene', False)}")
print(f"VIP gene: {gene.get('vip', False)}")
print(f"Description: {str(gene.get('summaries', [{}])[0].get('html', ''))[:200]}")

# Drug relationships for a gene
def get_gene_drug_relationships(gene_symbol):
    r = requests.get(f"{BASE}/drugLabel",
                     params={"gene": gene_symbol, "view": "base"})
    r.raise_for_status()
    return r.json()

data_labels = get_gene_drug_relationships("CYP2D6")
print(f"\nCYP2D6 drug label annotations: {data_labels['count']}")
for dl in data_labels["data"][:5]:
    print(f"  {dl.get('drug', {}).get('name'):25s} Source: {dl.get('source')}")

Query 4: PharmGKB Pathways

Retrieve pharmacogenomic pathways with gene roles.

import requests, pandas as pd

BASE = "https://api.pharmgkb.org/v1"

def get_pathways(drug=None, gene=None):
    params = {"view": "base"}
    if drug:
        params["drug"] = drug
    if gene:
        params["gene"] = gene
    r = requests.get(f"{BASE}/pathway", params=params)
    r.raise_for_status()
    return r.json()

# Warfarin pharmacogenomic pathway
data = get_pathways(drug="warfarin")
print(f"Warfarin pathways: {data['count']}")
for pw in data["data"][:3]:
    print(f"\n  Pathway: {pw.get('name')}")
    print(f"  Type: {pw.get('type')}")
    print(f"  PharmGKB ID: {pw.get('id')}")

Query 5: Drug Label Annotations (FDA/EMA)

Retrieve FDA and EMA drug label pharmacogenomic annotations.

import requests, pandas as pd

BASE = "https://api.pharmgkb.org/v1"

def get_drug_labels(drug=None, gene=None, source=None):
    params = {"view": "base"}
    if drug:
        params["drug"] = drug
    if gene:
        params["gene"] = gene
    if source:
        params["source"] = source  # "FDA", "EMA", "HCSC", etc.
    r = requests.get(f"{BASE}/drugLabel", params=params)
    r.raise_for_status()
    return r.json()

# FDA labels mentioning TPMT
data = get_drug_labels(gene="TPMT", source="FDA")
print(f"FDA drug labels with TPMT: {data['count']}")

rows = []
for dl in data["data"][:10]:
    rows.append({
        "drug": dl.get("drug", {}).get("name"),
        "source": dl.get("source"),
        "pgx_level": dl.get("pgxLevel"),
        "testing_required": dl.get("testingRequired"),
    })
df = pd.DataFrame(rows)
print(df.to_string(index=False))

Query 6: Variant Drug Associations

Retrieve all associations for a specific genetic variant.

import requests, pandas as pd

BASE = "https://api.pharmgkb.org/v1"

def search_variant(rsid):
    """Look up a variant by rsID and get all associations."""
    # First find the variant record
    r = requests.get(f"{BASE}/variant", params={"name": rsid, "view": "base"})
    r.raise_for_status()
    return r.json()

# VKORC1 variant (warfarin dose)
data = search_variant("rs9923231")
print(f"rs9923231 records: {data['count']}")

if data["data"]:
    v = data["data"][0]
    print(f"  Variant: {v.get('name')}")
    print(f"  PharmGKB ID: {v.get('id')}")

# Get clinical annotations for this variant
r2 = requests.get(f"{BASE}/clinicalAnnotation",
                  params={"variant": "rs9923231", "view": "base"})
anns = r2.json()
print(f"  Clinical annotations: {anns['count']}")
for ann in anns["data"][:5]:
    print(f"    Drug: {ann.get('drug', {}).get('name'):15s} Level: {ann.get('evidenceLevel')} | {ann.get('phenotype')}")

Key Concepts

PharmGKB Evidence Levels

Clinical annotation levels range from 1A (highest evidence: multiple clinical guideline associations) to 4 (case reports, biological plausibility only):

• 1A/1B: CPIC/DPWG guideline-level evidence
• 2A/2B: Replicated or single study with moderate evidence
• 3: Limited evidence (single study or case reports)
• 4: Case reports only

CPIC vs. DPWG Guidelines

CPIC (US-based) and DPWG (Netherlands-based) are the two primary bodies issuing genotype-based prescribing guidelines. Both are integrated in PharmGKB. CPIC focuses on actionable guidelines when PGx testing is already done; DPWG guidelines inform clinical decisions in the Netherlands.

Common Workflows

Workflow 1: Pharmacogene Drug Interaction Summary

Goal: For a patient's pharmacogene panel, retrieve all actionable drug-gene interactions with evidence levels.

import requests, pandas as pd, time

BASE = "https://api.pharmgkb.org/v1"

# Patient's relevant pharmacogenes
pharmacogenes = ["CYP2D6", "CYP2C19", "CYP2C9", "DPYD", "TPMT", "SLCO1B1"]

rows = []
for gene in pharmacogenes:
    r = requests.get(f"{BASE}/clinicalAnnotation",
                     params={"gene": gene, "level": "1A", "view": "base"})
    if r.ok:
        data = r.json()
        for ann in data["data"]:
            rows.append({
                "gene": gene,
                "drug": ann.get("drug", {}).get("name"),
                "phenotype": ann.get("phenotype"),
                "level": ann.get("evidenceLevel"),
                "significance": ann.get("clinicalSignificance"),
            })
    time.sleep(0.2)

df = pd.DataFrame(rows)
df = df.sort_values(["gene", "drug"])
df.to_csv("pharmacogene_drug_interactions.csv", index=False)
print(f"1A-level drug-gene interactions: {len(df)}")
print(df[["gene", "drug", "phenotype", "level"]].head(10).to_string(index=False))

Workflow 2: Guideline Compliance Check for Drug Panel

Goal: Given a list of prescribed drugs, identify which have CPIC guidelines and flag for PGx review.

import requests, pandas as pd, time

BASE = "https://api.pharmgkb.org/v1"

# Patient's drug list
drugs = ["warfarin", "clopidogrel", "codeine", "simvastatin",
         "metoprolol", "omeprazole", "azathioprine"]

rows = []
for drug in drugs:
    r = requests.get(f"{BASE}/guideline",
                     params={"drug": drug, "view": "base"})
    if r.ok:
        guidelines = r.json()["data"]
        cpic_count = sum(1 for g in guidelines if "CPIC" in g.get("source", ""))
        dpwg_count = sum(1 for g in guidelines if "DPWG" in g.get("source", ""))
        rows.append({
            "drug": drug,
            "has_guideline": len(guidelines) > 0,
            "cpic": cpic_count,
            "dpwg": dpwg_count,
            "total_guidelines": len(guidelines),
        })
    time.sleep(0.2)

df = pd.DataFrame(rows)
df = df.sort_values("total_guidelines", ascending=False)
print("Drug PGx Guideline Coverage:")
print(df.to_string(index=False))
df.to_csv("drug_pgx_coverage.csv", index=False)

Key Parameters

gene

drug

level

"1A"

"1B"

"2A"

"2B"

"3"

"4"

variant

source

"FDA"

"EMA"

"HCSC"

view

"base"

"base"

"max"

Best Practices

1. Start with Level 1A/1B annotations: Use

   level=1A

   filter to retrieve only the highest-evidence actionable annotations for clinical workflows; Level 3-4 annotations have limited actionability.

2. Use

   view=max

   for full details: Default

   view=base

   returns summary fields;

   view=max

   returns nested gene objects, full phenotype text, and linked resources (larger payload but more complete).

3. Check CPIC guidelines separately: Not all drugs with clinical annotations have CPIC guidelines; always check

   get_guidelines()

   in addition to

   get_clinical_annotations()

   for prescribing decisions.

4. Cross-reference with FDA label annotations: FDA pharmacogenomic labeling (

   get_drug_labels(source="FDA")

   ) reflects regulatory requirements; higher binding than CPIC recommendations in many clinical contexts.

5. Handle API rate limits gracefully: Add

   time.sleep(0.2)

   between requests for batch queries; use

   try/except

   to handle occasional API errors gracefully.

Common Recipes

Recipe: All Drugs with CPIC Level 1A Evidence

When to use: Build a list of all drugs with highest-evidence pharmacogenomic guidelines.

import requests, pandas as pd

r = requests.get("https://api.pharmgkb.org/v1/clinicalAnnotation",
                 params={"level": "1A", "view": "base"})
data = r.json()
print(f"Total Level 1A annotations: {data['count']}")
rows = [{"gene": a.get("gene", {}).get("symbol"),
         "drug": a.get("drug", {}).get("name"),
         "phenotype": a.get("phenotype")}
        for a in data["data"]]
df = pd.DataFrame(rows).drop_duplicates()
print(df.sort_values("gene").head(10).to_string(index=False))

Recipe: CPIC Guideline URL for a Drug

When to use: Get the direct PDF link to a CPIC guideline for a prescribing decision.

import requests

drug = "tacrolimus"
r = requests.get("https://api.pharmgkb.org/v1/guideline",
                 params={"drug": drug, "source": "CPIC", "view": "base"})
for gl in r.json()["data"]:
    print(f"{gl.get('name')}")
    print(f"  URL: {gl.get('url')}")

Recipe: Variant Clinical Significance Summary

When to use: Quick lookup of clinical annotations for a specific rsID.

import requests

rsid = "rs4149056"  # SLCO1B1*5 - statin myopathy
r = requests.get("https://api.pharmgkb.org/v1/clinicalAnnotation",
                 params={"variant": rsid, "view": "base"})
data = r.json()
print(f"{rsid}: {data['count']} clinical annotations")
for ann in data["data"][:5]:
    print(f"  [{ann['evidenceLevel']}] {ann.get('drug', {}).get('name')}: {ann.get('phenotype')}")

Troubleshooting

data

count

data

pageNum

pageSize

drug

ann.get("drug")

drug["name"]

view=max

view=base

view=max

Related Skills

• clinvar-database

  — Germline pathogenicity for variants found in PharmGKB (complementary)

• opentargets-database

  — Drug-target associations and safety data for pharmacogenomic targets

• chembl-database-bioactivity

  — Bioactivity and binding data for drugs annotated in PharmGKB

• fda-database

  — openFDA adverse event reports linked to pharmacogenomic risk factors

References

• PharmGKB website — Official database and knowledge portal
• PharmGKB REST API documentation — Full API endpoint reference
• CPIC guidelines — Clinical Pharmacogenomics Implementation Consortium
• Relling & Klein (2011) Nature Reviews Drug Discovery — PharmGKB foundational paper