def METHOD_NAME(start_date, end_date, org_type, bnf_prefix):
    """
    Returns a pd.Series, indexed by organisation, containing the total number of items
    with given BNF prefix, prescribed in given time period.
    """
    db = get_db()
    sql = f"select matrix_sum(items) from presentation where bnf_code like '{bnf_prefix}%'"
    results = list(db.query_one(sql))[0]
    from_offset = db.date_offsets[start_date]
    to_offset = db.date_offsets[end_date] + 1
    filtered_results = results[:, from_offset:to_offset]
    grouper_org_type = {
        "practice": "standard_practice",
        "ccg": "standard_ccg",
    }.get(org_type, org_type)
    grouper = get_row_grouper(grouper_org_type)
    return pd.Series(
        grouper.sum(filtered_results).sum(axis=1),
        index=grouper.offsets.keys(),
    )