Fix various issues with pharmacokinetics, improved parameters, distinction between adult/child

src/constants/defaults.ts

@@ -26,7 +26,7 @@ const versionInfo = versionJsonDefault && Object.keys(versionJsonDefault).length
       gitDate: 'unknown',
     };
 
-export const LOCAL_STORAGE_KEY = 'medPlanAssistantState_v7';
+export const LOCAL_STORAGE_KEY = 'medPlanAssistantState_v8'; // Incremented for ageGroup + renalFunction fields
 export const PROJECT_REPOSITORY_URL = 'https://git.11001001.org/cbaoth/med-plan-assistant';
 export const APP_VERSION = versionInfo.version;
 export const BUILD_INFO = versionInfo;
@@ -39,11 +39,23 @@ export const DEFAULT_F_ORAL = 0.96;
 
 // Type definitions
 export interface AdvancedSettings {
+  standardVd: { preset: 'adult' | 'child' | 'custom'; customValue: string }; // Volume of distribution (L)
   weightBasedVd: { enabled: boolean; bodyWeight: string }; // kg
   foodEffect: { enabled: boolean; tmaxDelay: string }; // hours
   urinePh: { enabled: boolean; phTendency: string }; // 5.5-8.0 range
   fOral: string; // bioavailability fraction
   steadyStateDays: string; // days of medication history to simulate
+  // Age-specific pharmacokinetics (Research Section 5.2)
+  // Children (6-12y) have faster elimination: t½ ~9h vs adult ~11h
+  ageGroup?: {
+    preset: 'child' | 'adult' | 'custom';
+  };
+  // Renal function effects (Research Section 8.2, FDA label 8.6)
+  // Severe impairment extends half-life by ~50% (11h → 16.5h)
+  renalFunction?: {
+    enabled: boolean;
+    severity: 'normal' | 'mild' | 'severe';
+  };
 }
 
 export interface PkParams {
@@ -57,6 +69,7 @@ export interface DayDose {
   time: string;
   ldx: string;
   damph?: string; // Optional, kept for backwards compatibility but not used in UI
+  isFed?: boolean; // Optional: indicates if dose is taken with food (delays absorption ~1h)
 }
 
 export interface DayGroup {
@@ -121,9 +134,10 @@ export const getDefaultState = (): AppState => ({
     damph: { halfLife: '11' },
     ldx: {
       halfLife: '0.8',
-      absorptionHalfLife: '0.9' // changed from 1.5, better reflects ~1h Tmax
+      absorptionHalfLife: '0.7' // Updated from 0.9 for better ~1h Tmax of prodrug
     },
     advanced: {
+      standardVd: { preset: 'adult', customValue: '377' }, // Adult: 377L (Roberts 2015), Child: ~150-200L
       weightBasedVd: { enabled: false, bodyWeight: '70' }, // kg, adult average
       foodEffect: { enabled: false, tmaxDelay: '1.0' }, // hours delay
       urinePh: { enabled: false, phTendency: '6.0' }, // pH scale (5.5-8.0)
@@ -144,7 +158,7 @@ export const getDefaultState = (): AppState => ({
     }
   ],
   steadyStateConfig: { daysOnMedication: '7' }, // kept for backwards compatibility, now sourced from pkParams.advanced
-  therapeuticRange: { min: '5', max: '25' }, // widened from 10.5-11.5 to general adult range
+  therapeuticRange: { min: '', max: '' }, // Empty by default - users should personalize based on their response
   doseIncrement: '2.5',
   uiSettings: {
     showDayTimeOnXAxis: '24h',
@@ -154,7 +168,7 @@ export const getDefaultState = (): AppState => ({
     yAxisMax: '',
     simulationDays: '5',
     displayedDays: '2',
-    showTherapeuticRange: true,
+    showTherapeuticRange: false,
     steadyStateDaysEnabled: true,
     stickyChart: false,
   }