I took ponstan, can I take beer after 2 hours?

Drug interaction with Alcohol Consumption 
Alcohol comprises a chemical substance that has many harmful side effects especially on Gut, Liver and the brain. Taking alcohol will ultamitly predispose to a state of liver damage on the long term, being alive with a vulnarable liver should get your attention to which medications you should use. Alcohol has many interactions with drugs and herbals especially NSAIDS (eg: Ponstan: Mefenamic acid) and Acetaminophen that may cause a state of acute liver failure especially if mixed together of taken with a very limited time ( less than 12 hrs ), so you are adviced to take any drug with alcohol and if symptomes of acute interaction happened like : Nausea, vomiting, losing balance, hedache and loss of coordination you should consult your treating family doctor.
Guidelines to prevent Alcohol drug interactions 

Most drugs are safe and effective when used as prescribed , it's a must you read warning instructions  on all medications. Many over the counter  medications for cough , cold, and hedache contain more than one ingredient that might have an interaction with alcohol. So if you are not sure about the anticipated interactions you should ask your doctor of pharmacist
Our advice
Alcohol is a proved health hazard that should be avoided especially if you are having a chronic medical condition, so it should be abstained with follow up with alcohol abstinance specialist.