It is certainly possible for a student who has not taken (or not completed) Introductory Logic to take and successfully complete Intermediate Logic. Though the Intermediate Logic text is designed as a continuation to Introductory Logic, it does not assume a mastery of the concepts in it. Almost all of the concepts from Introductory Logic that are essential for Intermediate Logic are re-taught (the only exceptions being the definitions of logical argument, premise, and conclusion; definitions assumed in Intermediate Logic, Lesson 7, but taught explicitly in Introductory Logic, Lesson 19).

That being said, a new Intermediate Logic student who is familiar with Introductory Logic will have an advantage over a student who is not. The following concepts from Introductory Logic are repeated and re-taught in Intermediate Logic (the concepts are first taught in the respective given lesson numbers):

1. The definition of logic (Introduction of both Intro and Inter)
2. The definition of a proposition or statement (Intro 6, Inter 1)
3. The parts of a conditional statement: antecedent and consequent (Intro 31, Inter 4)
4. Implication (Intro 9, Inter 4)
5. Logical equivalence (Intro 9, Inter 6)
6. Tautology and self-contradiction (Intro 7, Inter 6)
7. Validity (Intro 23, Inter 7)
8. Consistency (Intro 9, Inter 10)
9. Hypothetical syllogisms, modus ponens, modus tollens (Intro 31, Inter 13).

Also, though not explicitly mentioned in Intermediate Logic, an understanding of the concept of counterexamples (Intro 24) is helpful in understanding how truth tables show a propositional argument to be valid or invalid (Inter 7).

Given this, I would suggest for a student starting Intermediate Logic to read through the following lessons in Introductory Logic:

Lesson 31: Hypothetical syllogisms

A familiarity with the concepts in these lessons will benefit the new Intermediate Logic student.