I do not think cost plays such a major role in the prescription of drugs in the NHS as some people seem to think. Of course cost is taken into account where reasonable. So you might find one day that your expensive newish drug has been replaced by a cheaper generic drug, which is virtually the same, and for most people does not pose a problem, For the few , who find the generic less effective, they can request reinstatement of the original drug (and are entitled to this)
,Artane is usually prescribed for the tremor of PD and it relaxes the muscles It has, however, potentially some nasty side effects, probably these could outweigh the benefits of the drug. Memory problems, even psychiatric problems or a degree of cognitive dysfunction , especially in older people or among patients in long term treatment of this drug. With access to newer drugs and more experience (after all, every patient is different and often their treatment is too, so it takes time). I think, that the majority of neurologists find that the relief of certain PD symptoms is not sufficiently great to offset the potential for these unpleasant, unwanted side effects.