Why did Venkman have sedatives on his date with Dana?

The official Richard Mueller novelisation describes him hunting around in her apartment for medical supplies. Quite why she has powerful sedatives on hand isn't explained in any detail although someone who lives in "spook central" could feasibly be suffering from insomnia, hearing voices, mild paranoia or migraines, all of which are treatable with Thorazine:

Dana Barrett still floated above the bed while Peter Venkman rummaged through the drawers of her dresser. "She’s an artist", he thought. "She’s got to have some Valium somewhere."

It's worth noting that Louis was buying painkillers by the bucketload to deal with his headaches.

“I have acetylsalicylic acid but I get the generic from Walgreen’s cause I can get six hundred tablets for thirty-five percent less than the cost of three hundred of the name brand. Do you have a headache?”