Which of the following is known to cause severe pain on injection?

Thiopentone on extravasation or intraaerial injection cause intense pain and even necrosis. Pentothal (Thiopental Sodium for Injection) is an ultrasho-acting depressant of the central nervous system which induces hypnosis and anesthesia, but not analgesia. It produces hypnosis within 30 to 40 seconds of intravenous injection Too rapid injection may be followed by an alarming fall in blood pressure even to shock levels. Pentothal is administered by the intravenous route only. Slow injection is recommended to minimize respiratory depression and the possibility of overdosage.