Ptolemy IV. Philopator came to the throne after his father Ptolemy III. and his government changed the internal and international situation in a way that meant the end of the previous boom. The international influence of Egypt decreased under Ptolemy IV rule, came economic difficulties and Pharaoh's power weakened.
Ptolemy IV. initially ruled with his mother. The chief minister Sosibius had considerable power under his rule. He was the one who was behind the assassination of leading members of the royal family King's mother Berenice, King's brother Magas and uncle Lysimachus belonged among his victims. He also "left his marks" on the death of Cleomenes III, who committed suicide after a failed uprising against Sosibius and his children, mother and women from his surroundings were eliminated without exception.
Fourth Syrian war
Like his father, Ptolemy IV led the war with the Syrian ruler, who was Antiochus III. at that time. A forceful Seleucid ruler initially reached significant achievements in this fourth Syrian war (221 - 217 BC), however his campaign ended in the battle of Raphia in 217 BC. It was just Sosibius, the commander of the infantry, who had much of the credit for the victory of Ptolemaic troops. Egypt retained southern Syria after this victory, but it could not prevent Antiochus III from re-strengthening of Syrian positions in the east.
Ptolemy IV's death ended a period of great power and economic prosperity of Egypt. According to some Egyptologists he was the worst ruler of the dynasty. Rather than the government he took care of feast and drinking bouts, which ended by orgies and he was given the nickname Tryphon ("spendthrift") by his Greek subjects.