Osteoporosis and Porphyria
The following principles should be borne in mind when embarking on treatment for osteoporosis in patients with porphyria:
- Many of these patients are the women over the age of 50. In many cases, they will have been diagnosed as having porphyria 30 years and more previously. Remember that diagnostic testing was often inaccurate in the past; mistakes still occur today. It is important to review the diagnosis of porphyria in every patient requiring treatment for osteoporosis. In most cases, it is reasonable to repeat the diagnostic testing modern methods and confirm the diagnosis.
- A sensible approach to the management of osteoporosis involves stepped-care as follows: calcium supplementation, hormonal replacement therapy, bisphosphonates. It is wise to introduce agents one at a time according to this schedule, rather than to embark on across-the-board therapy with several agents at once. In this way, the safety and duration of individual agents can be assessed.
Dietary supplementation with milk, cheese or mineral calcium in tablet form (as elemental calcium, calcium carbonate or gluconate) is safe.
Hormonal Replacement Therapy
Female sex hormones may be dangerous in patients with variegate porphyria (VP) or acute intermittent porphyria (AIP). They should never be lightly prescribed as they may induce a life-threatening acute attack of porphyria. There is clear evidence that oestrogens and gestagens have induced the acute attack in some susceptible individuals with very serious consequences. The risk is greater in patients with AIP than in those with VP, and gestagens appear to be more dangerous than oestrogens. Many patients with VP will however tolerate oestrogens and even combined preparations, but unfortunately such a happy outcome cannot be guaranteed. It is essential to follow the guidelines below when prescribing them.
For further information: Hormonal therapy and family planning in porphyria
All members of this class are regarded as safe, as they are essentially not metabolised within the body.
Both vitamin D and calcitonin are likely to be safe.
Precautions to Follow When Introducing Drugs of Unproven Safety
This includes the use of oestrogen and gestagens in particular.
- Introduce agents one at a time.
- Warn the patient that the agent is not guaranteed safe; obtain their consent for its use; warn them to cease medication and report back to you immediately in the event that they develop abdominal pain.
- Where hormonal supplementation is prescribed, use an oestrogen-only preparation such as Premarin, particularly if the patient has had a hysterectomy. If you regard it as important to use a combined oestrogen-gestagen preparation, extra caution is necessary. Use the lowest possible dose and follow the patient closely.
- Avoid the use of hormonal therapy, particularly gestagens, in patients with AIP and in those with a history of more severe porphyria, especially those who have suffered acute attacks within the past few years.