NOVELTY - Immediate release solid oral dosage form comprises several particles, where each particle comprises (a) an active agent, and a material that is sensitive to acidic pH, where the dosage form releases at least 70% of the active agent within 45 minutes as measured by in vitro dissolution in a USP apparatus 2 (paddle) at 50 revolutions per minute (rpm) in 500 ml 0.1 N hydrochloric acid (HCl) at 37 degrees C.    USE - The immediate release solid oral dosage form is useful for delivering active agent chosen from opioid agonists, tranquilizers, CNS depressants, CNS stimulants, sedative hypnotics, and their mixtures, preferably opioid agonist for treating a disease or condition, preferably pain in patient. The opioid agonist is chosen from codeine, morphine, oxycodone, oxymorphone, hydrocodone, hydromorphone, and their salts, and their mixtures. The active agent is an opioid analgesic, preferably oxycodone hydrochloride. The immediate release solid oral dosage form is in the form of tablet or capsule (all claimed).    ADVANTAGE - The immediate release solid oral dosage form controls abuse potential of opioid analgesic which is resistant to parenteral and nasal abuse.    DETAILED DESCRIPTION - Immediate release solid oral dosage form comprises several particles, where each particle comprises (a) an active agent, and a material that is sensitive to acidic pH, where the dosage form releases at least 70% of the active agent within 45 minutes as measured by in vitro dissolution in a USP apparatus 2 (paddle) at 50 revolutions per minute (rpm) in 500 ml 0.1 N hydrochloric acid (HCl) at 37 degrees C, or (b) an opioid agonist, and a material that is sensitive to acidic pharmaceuticals, where several particles are dispersed in a matrix comprising a gelling agent, and a disintegrant, the dosage form releases at least 70% of the opioid agonist within 45 minutes as measured by in vitro dissolution in United States Pharmacopeia (USP) apparatus 2 (paddle) at 50 rpm in 500 ml 0.1N HCl at 37 degrees C, and the viscosity of the dosage form mixed with from 0.5-10 ml of distilled water prevents the opioid agonist from being systemically absorbed, or reduces the ability of the opioid agonist to be systemically absorbed, when administered by the parenteral or nasal route. INDEPENDENT CLAIMS are included for the following:    (1) process for preparing the immediate release solid oral dosage form, involves (a) preparing several particles, and (b) granulating an active agent and a material sensitive to acidic pH to obtain a granulation, compressing the granulation into a tablet or containing the granulation in a capsule; and    (2) use of a polymer sensitive to acidic pH in combination with a gelling agent to impart tamper resistance in an immediate release solid oral dosage form, where polymer is chosen from acrylic copolymers including amino-, and/or monoalkylamino-, and/or dialkylamino groups.