Abstract: The invention provides a novel and efficient means for the administration of a therapeutically effective ingredient by rectal application in the form of a medicament capsule encapsulating the effective ingredient. The medicament capsule according to the invention is formed of a hard capsule shell made of a mixed ester of a cellulose ether, e.g. alkyl-, hydroxyalkyl- and hydroxyalkyl alkylcelluloses, esterified with aliphatic monacyl groups and acidic succinyl groups. When the capsule is inserted into the rectum, the capsule shell is disintegrated and the rectally absorbable effective ingredient is readily and smoothly released into the rectum and absorbed to exhibit therapeutical effects as efficiently as with conventional suppositories.