According to Drugs.com, a pill with "TL 177" imprinted on it is a 10-milligram dose of a drug known as cyclobenzaprine hydrochloride, or Flexeril. Flexeril is used as a short-term treatment for muscle spasms, as stated by WebMD.
WebMD states that Flexeril is usually taken three times per day or as directed by a doctor. Potential side effects listed by WebMD include dizziness, dry mouth, drowsiness and constipation. It is recommended that people taking Flexeril not drive or operate heavy machinery until they know how the medication affects them. WebMD states that it is possible for the risk of side effects to increase if this medication is taken incorrectly or for longer than prescribed.