No insurance company or health service corporation may deliver, issue, execute, or renew any health insurance policy or medical service contract that includes coverage of medical benefits on a group, blanket, franchise, or association basis unless the insurer makes available, at the option of the policyholder, the following coverages for which an additional premium may be charged:

1. All drugs and medicines prescribed by the provider of health services.

2. Services rendered and care administered by chiropractors licensed under chapter 43-06.