Advising on complementary products and conventional medicines

Place of complementary products

Complementary products are used alongside conventional medicine and should not replace conventional medicine.

When a complementary product is used in place of a conventional medicine, this is known as alternative treatment.

Almost all alternative treatments are not supported by the NHS due to weak or no evidence of effectiveness.

NICE advise that complementary products should be part of medicines reconciliation and medication reviews.

Before contacting SPS

Complete the stepwise process in the SPS article Managing complementary products and conventional medicines

There may be occasions when you need to contact SPS for further advice. Such as when you cannot find the product in the resources listed in the SPS article Complementary products: resources to support answering questions.

Stop the product or do not start it

In the following examples you may advise the person to stop their complementary product or avoid starting it. The list is not exhaustive, and decisions should be made on a case-by-case basis.

Altered efficacy

There is a pharmacodynamic or pharmacokinetic interaction which reduces the effectiveness of the conventional medicine. The risk posed to the person from reduced effectiveness of their conventional medicine is considered high or harmful.

Example

St John’s Wort (SJW) reduces the effect of oral contraceptives and risks contraceptive failure and an unwanted pregnancy.

SJW also reduces the effects of ciclosporin used for transplants and risks organ rejection.

Side effects

There is an increase in side effects due to additive pharmacodynamic effects or interference with drug metabolism.

Example

Ginkgo biloba, garlic and glucosamine have antiplatelet activity and can increase the effects of warfarin, direct-acting oral anti-coagulants (DOACs) and antiplatelets.

People may be at a higher risk of side effects such as prolonged bleeding time and easy bruising.

Complementary products can enhance the effects of conventional medicines, and vice versa.

Antidepressants such as serotonin selective reuptake inhibitors (SSRIs) can increase the risk of serotonin syndrome with SJW.

Amitriptyline can enhance the sedating effects of valerian.

High risk condition

People who take multiple conventional medicines may face a higher risk of side effects, interactions, complications, or treatment failure.

Example

Red rice yeast contains monacolin K which may increase the risk of rhabdomyolysis with atazanavir and ritonavir.

High risk medicine

Using complementary products alongside conventional medicines with limited pharmacokinetic pathways or a narrow therapeutic index (NTI) could increase the risk of treatment failure, toxicity, or organ damage.

Example

Kava can cause liver toxicity and impair the metabolism of medicines such as paracetamol and statins.

Phenytoin is metabolised by the liver and has a NTI. Small changes in phenytoin levels could cause toxicity or sub therapeutic levels leading to seizures. Ginkgo may decrease phenytoin levels by inducing cytochrome P450 enzymes.

Banned ingredient

The MHRA has a list of banned complementary ingredients based on concerns over toxicity, side effects or lack of safety data.

Example

Aristolochia species contain aristolochic acid which can cause kidney damage and is carcinogenic.

Poor quality product

If the quality or source of a complementary product cannot be verified, there is a risk it may be contaminated or adulterated.

The product could potentially contain heavy metals, undeclared active pharmaceutical ingredients, or inert substances.

Example

Traditional Chinese Medicine products have been found to contain steroids when claiming treatment of skin conditions.

Other undeclared active pharmaceutical ingredients in complementary products include NSAIDs and sildenafil.

Stopping products

If the person decides to stop the complementary product, advise them how to withdraw it safely.

You can sometimes find stopping information in the monographs of complementary ingredients. Use the resources listed in the SPS article Complementary products: resources to support answering questions to find published advice.

Example

SJW should be tapered gradually to reduce the risk of withdrawal symptoms.

Also consider the impact of stopping the complementary product on the conventional medicine with regards to changes in enzyme induction and inhibition.

Continue the product or start it

No interaction information does not mean there is no interaction possible. It implies that the potential for an interaction is unknown.

The complementary product should aways be taken at the recommended dose.

The total recommended daily amount of complementary ingredients should not be exceeded.

The complementary product should be added to all medicine lists.

Example reasons

• The person has been on the complementary product for several months or years alongside the same conventional medicines without incident.
• The expectation of a harmful interaction between the complementary product and conventional medicine is low based on the interaction information available.
• There are some concerns about interactions and the person has been counselled on what to monitor and report.

Counselling

Always counsel people who are taking conventional medicines and starting or continuing a complementary product.

Points to include

• Do not stop taking your conventional medicines without consulting your healthcare professional.
• Choose a complementary product that has manufacturing quality assured to avoid the risk of adulteration.
• Purchase the complementary product from a reputable source to avoid fake products.
• Stick with the same complementary product as ingredients can vary even if the brand name is the same.
• Follow the instructions as stated on the complementary product label.
• Store the complementary product like conventional medicines and keep them out of the reach of children.
• Follow any special storage requirements found on the complementary product label or information leaflet.
• Report any new or worsening symptoms to your healthcare practitioner (including your complementary product advisor) and the MHRA Yellow Card Scheme.
• List all complementary products, over-the-counter, and prescribed medicines on your medicine lists.

If the complementary product interacts with the person’s conventional medicine and they still decide to continue taking the product, consider what additional monitoring will be required.

Monitoring

Consider baseline tests if the complementary product is known to affect liver function, kidney function or electrolyte levels.

Ask the person to watch out for changes in their symptoms or new symptoms, and to report these to their healthcare professional and the MHRA through the Yellow Card Scheme.

Consider scheduling a review to assess the clinical status of people who decide to start a complementary product against the advice of their healthcare professional.

Example

Liver function tests (LFTs) before starting red yeast rice as it is used to lower cholesterol but can also cause liver toxicity and muscle damage.

Further advice

Contact the SPS Medicines Advice Service if the steps in the SPS article Managing complementary products and conventional medicines have not helped you reach a clinical decision.

When contacting SPS about interactions between complementary products and conventional medicines, provide information already gathered using our stepwise approach to avoid duplication of effort.

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