foreach ( wp_load_alloptions() as $option => $value ) {

    if ( strpos( $option, 'myplugin_' ) === 0 ) {

        delete_option( $option );

    }

}

​

global $wpdb;

​

$plugin_options = $wpdb->get_results( "SELECT option_name FROM $wpdb->options WHERE option_name LIKE 'myplugin_%'" );

​

foreach( $plugin_options as $option ) {

    delete_option( $option->option_name );

}

​