Is it OK to take Nyquil 4 hours after taking Sudafed if they do not contain the same active...

Sudafed is a brand name product available over the counter to treat symptoms of the common cold, sinusitis and nasal congestion. There are several formulations that contain different active ingredients including pseudoephedrine, phenylephrine, oxymetazoline, xylometazoline, ibuprofen, caffeine, guaifenesin and paracetamol (acetaminophen). Formulations vary depending on what country you are in.

Nyquil is also a brand name product available over the counter to treat cold and flu symptoms. Various formulations also exist containing combinations of ingredients including acetaminophen, dextromethorphan, and doxylamine. Nyquil severe also contains phenylephrine.

To provide an accurate answer and to ensure you are not overdosing on "similar" ingredients we would need to know the exact products you are referring to.
Ask your pharmacist for more advice.