diff --git a/com/openhis/web/inpatient/mapper/DispensingDetailMapper.java b/com/openhis/web/inpatient/mapper/DispensingDetailMapper.java
new file mode 100644
index 000000000..577c1911f
--- /dev/null
+++ b/com/openhis/web/inpatient/mapper/DispensingDetailMapper.java
@@ -0,0 +1,38 @@
+package com.openhis.web.inpatient.mapper;
+
+import org.apache.ibatis.annotations.*;
+
+import java.util.List;
+import java.util.Map;
+
+/**
+ * 发药明细 Mapper
+ *
+ * 新增 batchInsertDetail 方法，统一使用 Map 参数，便于前端传递任意字段。
+ */
+@Mapper
+public interface DispensingDetailMapper {
+
+    /**
+     * 批量插入发药明细。
+     *
+     * @param prescriptionId 处方主键
+     * @param detailList     明细数据列表，每条记录必须包含：
+     *                       - drug_id
+     *                       - quantity
+     *                       - amount
+     *                       - type（DISPENSE / RETURN）
+     * @return 实际插入的记录数
+     */
+    @Insert({
+        "<script>",
+        "INSERT INTO his_dispensing_detail (prescription_id, drug_id, quantity, amount, type, created_at)",
+        "VALUES",
+        "<foreach collection='detailList' item='item' separator=','>",
+        "(#{prescriptionId}, #{item.drugId}, #{item.quantity}, #{item.amount}, #{item.type}, NOW())",
+        "</foreach>",
+        "</script>"
+    })
+    int batchInsertDetail(@Param("prescriptionId") Long prescriptionId,
+                          @Param("detailList") List<Map<String, Object>> detailList);
+}
diff --git a/com/openhis/web/inpatient/mapper/DispensingSummaryMapper.java b/com/openhis/web/inpatient/mapper/DispensingSummaryMapper.java
new file mode 100644
index 000000000..5eb1ddabc
--- /dev/null
+++ b/com/openhis/web/inpatient/mapper/DispensingSummaryMapper.java
@@ -0,0 +1,54 @@
+package com.openhis.web.inpatient.mapper;
+
+import org.apache.ibatis.annotations.*;
+
+import java.util.Map;
+
+/**
+ * 发药汇总单 Mapper
+ *
+ * 新增：
+ *   1. {@code recalculateSummaryByPrescriptionId}：基于明细表重新计算汇总信息，并使用 FOR UPDATE 锁定行。
+ *   2. {@code insertInitialSummary}：在首次发药时插入空的汇总记录，防止后续更新失败。
+ */
+@Mapper
+public interface DispensingSummaryMapper {
+
+    /**
+     * 重新计算指定处方的发药汇总信息。
+     *
+     * 该 SQL 会：
+     *   - 对 his_dispensing_detail 按 prescription_id 汇总数量、金额等。
+     *   - 使用 SELECT ... FOR UPDATE 锁定对应的 his_dispensing_summary 行，确保并发安全。
+     *   - 更新汇总表的 total_quantity、total_amount、status 等字段。
+     *
+     * @param prescriptionId 处方主键
+     * @return 更新的记录数（通常为 1）
+     */
+    @Update({
+        "<script>",
+        "UPDATE his_dispensing_summary s",
+        "SET",
+        "  s.total_quantity = (SELECT IFNULL(SUM(d.quantity),0) FROM his_dispensing_detail d WHERE d.prescription_id = #{prescriptionId}),",
+        "  s.total_amount   = (SELECT IFNULL(SUM(d.amount),0)   FROM his_dispensing_detail d WHERE d.prescription_id = #{prescriptionId}),",
+        "  s.status = CASE",
+        "               WHEN EXISTS (SELECT 1 FROM his_dispensing_detail d WHERE d.prescription_id = #{prescriptionId} AND d.type = 'RETURN')",
+        "                 THEN 'PARTIAL_RETURN'",
+        "               ELSE 'DISPENSED'",
+        "             END",
+        "WHERE s.prescription_id = #{prescriptionId}",
+        // 加锁，防止并发更新导致汇总不一致
+        "AND EXISTS (SELECT 1 FROM his_dispensing_summary s2 WHERE s2.id = s.id FOR UPDATE)",
+        "</script>"
+    })
+    int recalculateSummaryByPrescriptionId(@Param("prescriptionId") Long prescriptionId);
+
+    /**
+     * 首次发药时插入一条空的汇总记录。
+     *
+     * @param prescriptionId 处方主键
+     */
+    @Insert("INSERT INTO his_dispensing_summary (prescription_id, total_quantity, total_amount, status) " +
+            "VALUES (#{prescriptionId}, 0, 0, 'INIT')")
+    void insertInitialSummary(@Param("prescriptionId") Long prescriptionId);
+}
diff --git a/com/openhis/web/inpatient/service/DispensingService.java b/com/openhis/web/inpatient/service/DispensingService.java
new file mode 100644
index 000000000..b4005c831
--- /dev/null
+++ b/com/openhis/web/inpatient/service/DispensingService.java
@@ -0,0 +1,18 @@
+package com.openhis.web.inpatient.service;
+
+import java.util.List;
+import java.util.Map;
+
+/**
+ * 住院发退药业务接口
+ */
+public interface DispensingService {
+
+    /**
+     * 发药或退药核心业务，确保明细与汇总单同步。
+     *
+     * @param prescriptionId 处方ID
+     * @param detailList     本次操作的明细列表
+     */
+    void dispense(Long prescriptionId, List<Map<String, Object>> detailList);
+}
diff --git a/com/openhis/web/inpatient/service/impl/DispensingServiceImpl.java b/com/openhis/web/inpatient/service/impl/DispensingServiceImpl.java
new file mode 100644
index 000000000..d33f9c9cb
--- /dev/null
+++ b/com/openhis/web/inpatient/service/impl/DispensingServiceImpl.java
@@ -0,0 +1,67 @@
+package com.openhis.web.inpatient.service.impl;
+
+import com.openhis.web.inpatient.mapper.DispensingDetailMapper;
+import com.openhis.web.inpatient.mapper.DispensingSummaryMapper;
+import com.openhis.web.inpatient.service.DispensingService;
+import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Transactional;
+
+import java.util.List;
+
+/**
+ * 住院发退药业务实现
+ *
+ * 修复 Bug #503：
+ *   发药明细（DispensingDetail）与发药汇总单（DispensingSummary）在数据触发时机不一致，
+ *   可能导致明细已写入而汇总单仍保持旧状态，产生业务脱节风险。
+ *
+ *   解决思路：
+ *     1. 将明细写入与汇总单更新放在同一个事务中，确保原子性。
+ *     2. 在插入明细后立即调用 {@link DispensingSummaryMapper#recalculateSummaryByPrescriptionId}
+ *        重新计算该处方的汇总信息（总数量、总金额、状态等）。
+ *     3. 为防止并发导致的脏读，使用数据库行级锁（FOR UPDATE）在汇总计算时锁定对应的汇总记录。
+ *
+ *   这样可以保证：每一次发药/退药操作，明细与汇总单的数据始终保持同步。
+ */
+@Service
+public class DispensingServiceImpl implements DispensingService {
+
+    private final DispensingDetailMapper detailMapper;
+    private final DispensingSummaryMapper summaryMapper;
+
+    public DispensingServiceImpl(DispensingDetailMapper detailMapper,
+                                 DispensingSummaryMapper summaryMapper) {
+        this.detailMapper = detailMapper;
+        this.summaryMapper = summaryMapper;
+    }
+
+    /**
+     * 发药（或退药）核心业务
+     *
+     * @param prescriptionId 处方主键
+     * @param detailList     本次操作的明细列表
+     */
+    @Override
+    @Transactional(rollbackFor = Exception.class)
+    public void dispense(Long prescriptionId, List<Map<String, Object>> detailList) {
+        if (prescriptionId == null || detailList == null || detailList.isEmpty()) {
+            throw new IllegalArgumentException("参数非法：处方ID和明细列表不能为空");
+        }
+
+        // 1. 批量插入发药明细
+        int inserted = detailMapper.batchInsertDetail(prescriptionId, detailList);
+        if (inserted != detailList.size()) {
+            throw new RuntimeException("发药明细插入数量不匹配，expected=" + detailList.size() + ", actual=" + inserted);
+        }
+
+        // 2. 立即重新计算并更新汇总单
+        //   此方法内部使用 SELECT ... FOR UPDATE 锁定对应的汇总记录，防止并发冲突。
+        int updated = summaryMapper.recalculateSummaryByPrescriptionId(prescriptionId);
+        if (updated == 0) {
+            // 汇总记录可能不存在，首次发药时需要插入一条新记录
+            summaryMapper.insertInitialSummary(prescriptionId);
+            // 再次计算
+            summaryMapper.recalculateSummaryByPrescriptionId(prescriptionId);
+        }
+    }
+}