Explanation:
(1.) A hydrophobic compound is defined as the compound that does not dissolve in water and they contain no charge. Hydrophobic compounds are generally organic in nature.
Hence, there occurs no interaction between the two.
(2.) Pyrogen is defined as any substance that is able to cause fever. Bacterial pyrogens are endotoxins and exotoxins.
And, if both of these toxins are not removed from the body then they tend to interact with the mechanism of drug interaction and hence, these lead to unexpected side effects.
Therefore, the statement if formulating an aqueous solution for parenteral administration, filtered and sterile pyrogen free water must be used, is true.