Tamper-resistant pharmaceutical compositions have been developed to reduce the likelihood of improper administration of drugs, especially drugs such as opioids. The tamper-resistant compositions retard the release of drug, even if the physical integrity of the formulation is compromised (for example, by chopping with a blade or crushing) and the resulting material is placed in water, snorted, or swallowed. However, when administered as directed, the drug is slowly released from the composition as the composition is passes through the GI tract.