Marathon interviews are becoming more common especially in the pharmaceutical industry. These interviews typically last all day and require a tremendous amount of preparation. Much like a typical marathon you must train yourself and plan ahead.
Check out Laura McMullen, Careers Editor at U.S. News, marathon interview training guide.

The Nature of the Interview
Acknowledge the nature of the interview. Most of the conversations will seem repetitive by the afternoon. You will be asked similar questions by each interviewer; shape each answer to the person sitting across from you.

Organization
Bring a padfolio with plenty of paper and pens, multiple copies of your CV or resume, and business cards. Not only will you need to organize your belongings, but you will also need to organize your thoughts.

Research
A list of who you will be meeting will definitely help with the preparation process and ease your mind. Once you receive this list you can conduct research on their backgrounds, interests, etc. Background information will allow you to connect with the interviewer, leaving a lasting impression.

Energy
The last thing you need while running into the last leg of the marathon is to feel groggy. To prevent any grogginess or even restlessness, eat a hearty, protein enriched breakfast.

Adaptability
You will be meeting with multiple people of different titles and each interview purpose will be different. For example meeting with the hiring manager vs. meeting with human resources will be very different. The hiring manager will dig into your skill-set and personality traits, while human resources will focus on how you would fit into the company as a whole.

Breaks
Use the scheduled breaks to sustain your enthusiasm and refer back to your training guide and schedule. Also, take a few minutes in between each interview to take a few breaths and prepare for the next round. Don’t forget to celebrate the little victories throughout the day.

Follow-up
After any interview, a thank-you note should be sent. Make sure to collect business cards and/or contact information on each person you speak with. Not sure what the thank-you note should entail or what else is required post-interview?

Check out the article What To Do After The Interview.

Source:

http://money.usnews.com/money/careers/articles/2014/09/25/how-to-crush-the-all-day-marathon-interview?page=2