Section 1: Introduction — The Question Nobody Asks

"Are you taking anything else?"

The question is asked at nearly every clinical encounter. The answer is almost always incomplete.

A 62-year-old woman with type 2 diabetes and hypertension attends her primary care clinic in Mandeville. Her medication list reads: metformin 500 mg twice daily, lisinopril 10 mg daily, aspirin 81 mg daily. Clean, controlled, unremarkable.

What the medication list does not show: she drinks cerasee tea every morning for her "sugar." Her neighbour gave her soursop leaf tea for her blood pressure. She takes guinea hen weed capsules from the market because her sister swears by them. On Sundays, she eats ackee and saltfish — Jamaica's national dish.

The cerasee is lowering her blood glucose on top of the metformin, creating unpredictable hypoglycaemic episodes she attributes to skipping meals. The soursop leaf is adding to the blood-pressure-lowering effect of her lisinopril, causing dizziness she hasn't mentioned. The guinea hen weed contains coumarin-like compounds that interact with her aspirin. And the ackee — if unripe — contains hypoglycin A, which can cause fatal hypoglycaemia.

None of this is in her chart. Nobody asked the right question. And even if they did, she might not have answered — because she doesn't consider these things medications. They are food. They are tea. They are what her grandmother used.

This is the bush medicine blind spot.

1.1 Why this report exists

Report 1 in this series — The Caribbean Clinical Interactions Atlas — dedicated one of its eight clinical themes to herbal interactions. That theme covered the headline risks: ackee, St. John's Wort, Aristolochia, kava kava, and a handful of others. It was a starting point.

This report goes deeper. It provides full monographs for eleven Caribbean herbs commonly used alongside prescription medicines, covering the pharmacology of each herb, the specific drug interactions documented in the literature, the clinical risk, and — critically — what to say to the patient. It also profiles ten internationally available herbal supplements that Caribbean patients purchase over the counter, from health food shops, or bring back from trips abroad.

The ElesRx database contains validated interactions for all herbs covered in this report. When a clinician enters a patient's full medication list — including herbal products — ElesRx flags the interactions automatically. The challenge is getting the herbs onto the list in the first place.

1.2 The scale of herbal use in the Caribbean

Herbal medicine use in the Caribbean is not a niche practice. It is mainstream. Studies across the region consistently find that 60–80% of Caribbean populations use herbal remedies, with the highest rates among older adults, women, and rural communities — precisely the populations most likely to be on multiple prescription medications.¹

In Jamaica, bush teas are part of daily life. Cerasee, fever grass, soursop leaf, guinea hen weed, and leaf of life are not exotic botanicals — they are kitchen staples. In Trinidad and Tobago, similar patterns hold with local variations. In the OECS states, herbal use is deeply embedded in both Afro-Caribbean and Indo-Caribbean healing traditions.

The problem is not that patients use herbs. It is that they do not tell their clinicians, and clinicians do not ask specifically enough. The standard question — "Are you taking any other medications?" — fails because patients do not categorise herbal teas, bush baths, and traditional remedies as medications. They are food, culture, and family tradition.

The question that works is specific: "Do you drink any bush teas? Do you take any supplements or natural remedies? Did anyone give you anything for your condition?"

Section 2: Eleven Caribbean Herbs — Full Monographs

Each monograph follows the same structure: common name and scientific name, traditional use, the active compounds that produce drug interactions, specific drug interactions with severity grades, clinical management, and a patient counselling script.

All interaction data is drawn from the ElesRx database and verified against PubMed, PMC, and the sources listed in Section 5.

2.1 Ackee (Blighia sapida)

Traditional use: National fruit of Jamaica. Eaten as a cooked dish (ackee and saltfish). Not used as medicine per se, but consumed as a staple food with pharmacological consequences when unripe.

Active compound: Hypoglycin A and hypoglycin B — amino acid derivatives found in unripe ackee arils and seeds. Hypoglycin A inhibits mitochondrial fatty acid beta-oxidation, causing severe, non-ketotic hypoglycaemia and metabolic acidosis.

Drug interactions:

Clinical risk: Jamaican Vomiting Sickness (JVS) — profuse vomiting, altered consciousness, hypoglycaemia, metabolic acidosis, hepatic failure, and death. JVS occurs from consumption of unripe ackee or ackee seeds. In a diabetic patient on oral hypoglycaemics, even mild hypoglycin exposure can trigger severe hypoglycaemia that is resistant to standard glucose correction because the mechanism is mitochondrial, not insulin-mediated.

Clinical management: Verify exposure details when ackee is consumed (ripeness at harvest and preparation method). Risk is concentrated in unripe fruit, forced-open fruit, and seeds. Counsel diabetic patients to use only naturally opened ripe ackee and to avoid seeds and pink membrane entirely.

Patient counselling script: "Ackee can be included in your diet when it has opened naturally and is prepared correctly. Do not eat ackee that was forced open, and never eat the seed or pink membrane. If you're on diabetes medication, unripe ackee can lower blood sugar dangerously and may be harder to correct. If you feel unwell after eating ackee — vomiting, confusion, or sweating — go to the emergency department and tell them you ate ackee."

2.2 Cerasee (Momordica charantia)

Traditional use: Commonly consumed as a bush tea in Jamaica and across the Caribbean. It is used for "cleaning the blood," glycaemic control, skin conditions, and general wellness. It is also referred to as bitter melon, bitter gourd, or karela in Indo-Caribbean communities.

Active compounds: Charantin (steroidal saponin), polypeptide-p (insulin-like peptide), and vicine — all of which have documented hypoglycaemic activity through multiple mechanisms including increased glucose uptake, glycogen synthesis, and enhanced insulin secretion.

Drug interactions:

Clinical risk: Hypoglycaemia may occur, including clinically significant episodes in patients using insulin or sulfonylureas, due to additive glucose-lowering effects. Risk may increase with frequent use because exposure is often regular and long term rather than occasional.

Clinical management: Take a medication-history approach that includes herbal intake details (frequency, preparation, quantity). Discuss possible additive glucose-lowering effects and incorporate this information into the care plan. Consider closer glucose follow-up, reinforcement of hypoglycaemia education, and medication review based on trends and symptoms.

Patient counselling script: "Cerasee may affect blood sugar, and your diabetes medicines also lower blood sugar. If you use cerasee, let us know how often and how you prepare it so we can interpret your readings accurately and adjust treatment if needed. If you develop symptoms such as shakiness, sweating, or confusion, check your blood sugar and seek care if symptoms continue."

2.3 Soursop Leaf (Annona muricata)

Traditional use: Tea made from dried soursop leaves, used in the Caribbean for hypertension, anxiety, sleep, and — widely but without clinical evidence — cancer prevention. Also used as an anti-inflammatory and digestive aid.

Active compounds: Annonaceous acetogenins (including annonacin), reticuline, and coreximine. Acetogenins demonstrate antihypertensive activity through vasodilation and possible calcium channel blockade in preclinical studies.

Drug interactions:

Clinical risk: Excessive hypotension — dizziness, lightheadedness, falls, syncope — particularly in elderly patients already on multiple antihypertensives. The risk is amplified in patients who are volume-depleted (from diuretics, heat, or inadequate fluid intake).

Clinical management: Ask about soursop leaf tea use in any patient with unexplained dizziness or postural hypotension. If the patient is on antihypertensives and drinking soursop tea regularly, consider whether the antihypertensive dose needs reduction rather than adding another drug.

Patient counselling script: "Soursop leaf can lower blood pressure, and your prescription medicine does the same. Together they may lower it too much, which can cause dizziness. Until we review your readings, reduce or pause the tea if you feel lightheaded. We'll monitor your blood pressure and adjust your treatment plan safely."

2.4 Guinea Hen Weed (Petiveria alliacea)

Traditional use: Also known as anamu. Used across Jamaica and the Caribbean as an immunostimulant, analgesic, antimicrobial, and anti-inflammatory. Taken as tea or in capsule form. Also used topically for skin conditions and insect repellent.

Active compounds: Naturally occurring coumarin derivatives, dibenzyl trisulphide, and various sulphur-containing compounds. The coumarins share structural similarity with warfarin.

Drug interactions:

Clinical risk: Increased INR and bleeding risk in patients on warfarin. Unusual bruising, prolonged bleeding from cuts, or gastrointestinal bleeding. The coumarin content varies by plant source, making the interaction unpredictable in dose-response terms.

Clinical management: Patients on warfarin should be asked specifically about guinea hen weed use. If concurrent use is identified, increase INR monitoring frequency. Guinea hen weed should be discontinued at least two weeks before planned surgery.

Patient counselling script: "Guinea hen weed contains natural blood-thinning compounds that can add to warfarin's effect and increase bleeding risk. While you are on warfarin, avoid guinea hen weed unless your care team advises otherwise. If you have been using it, we should check your INR more frequently."

2.5 Leaf of Life (Bryophyllum pinnatum)

Traditional use: Used in Jamaica and the Caribbean for asthma, coughs, colds, headaches, hypertension, and as a general sedative. Leaves are eaten raw, made into tea, or applied topically. Also known as "life plant" or "miracle leaf."

Active compounds: Bufadienolides, flavonoids (quercetin, kaempferol), and phenolic acids. Bufadienolides have documented sedative and muscle-relaxant properties. The plant also demonstrates antihypertensive activity in animal models.

Drug interactions:

Clinical risk: Excessive sedation when combined with benzodiazepines, opioids, or sedating antihistamines — particularly in elderly patients. Falls risk increases. In combination with antihypertensives, the risk is additive hypotension.

Clinical management: Ask about leaf of life use in patients with unexplained drowsiness or excessive sedation, particularly those on CNS depressants. If the patient is on a benzodiazepine (diazepam is common in the Caribbean) and using leaf of life regularly, the combined sedative effect may be the cause of daytime drowsiness.

Patient counselling script: "Leaf of life has sedative effects, and diazepam does as well. Taking both can increase drowsiness and falls risk, especially in older adults. Please let us know how often you use leaf of life so we can review your regimen and adjust treatment safely if needed."

2.6 Fever Grass (Cymbopogon citratus)

Traditional use: Lemongrass tea — one of the most commonly consumed bush teas across the Caribbean. Used for colds, fever, headaches, stomach complaints, and as a general calming tea.

Active compounds: Citral (geranial and neral), geraniol, and myrcene. Citral has demonstrated antihypertensive activity in animal studies through vasodilation and possible calcium antagonism.

Drug interactions:

Clinical risk: Low. Fever grass is generally lower risk from a drug interaction perspective. Its antihypertensive effect is usually mild at typical tea intake, but relevance increases in patients on multiple antihypertensives or in those who are volume-depleted.

Clinical management: No specific action needed in most patients. Note in the medication history if the patient drinks fever grass tea daily, particularly if they are on multiple antihypertensives and experiencing postural dizziness.

Patient counselling script: "Fever grass tea is generally lower risk, but it can still lower blood pressure slightly. Let your clinician know if you use it daily so it can be included in your medication history. If you notice dizziness or faintness, reduce intake and seek a blood pressure review."

2.7 Spanish Needle (Bidens pilosa)

Traditional use: Used in Jamaica and the Caribbean for diabetes, inflammation, wound healing, stomach complaints, and urinary tract infections. Taken as tea or applied topically as a poultice.

Active compounds: Polyacetylenes (including 1-phenyl-hepta-1,3,5-triyne), flavonoids, and tannins. The polyacetylenes have demonstrated hypoglycaemic and anti-inflammatory activity.

Drug interactions:

Clinical risk: Similar to cerasee — additive hypoglycaemia in diabetic patients on oral antidiabetics or insulin. The interaction is less well-characterised than cerasee because there is less clinical data, but the preclinical evidence is consistent.

Clinical management: Use the same structured approach as cerasee: document intake (frequency, preparation, quantity), review glucose trends, and consider medication adjustment if recurrent low readings or hypoglycaemic symptoms occur.

Patient counselling script: "Spanish needle may lower blood sugar. If you are using it with diabetes medicines, your glucose may fall lower than expected. Please tell us how often you use it so we can monitor your readings and adjust treatment safely if needed."

2.8 Periwinkle (Catharanthus roseus)

Traditional use: Used in Caribbean folk medicine for diabetes, hypertension, and — traditionally — cancer. The plant is the source of the vinca alkaloids vincristine and vinblastine, which are among the most important chemotherapy agents in modern oncology.

Active compounds: Vincristine, vinblastine, catharanthine, vindoline — potent cytotoxic alkaloids. The crude plant extract contains these alkaloids at variable and unpredictable concentrations.

Drug interactions:

Clinical risk: Bone marrow suppression (leucopenia, thrombocytopenia), peripheral neuropathy, and unpredictable cytotoxicity. The crude herb is not equivalent to pharmaceutical-grade vincristine — the concentration of alkaloids varies wildly, making any therapeutic use of the raw plant dangerous.

Clinical management: Patients should be strongly advised against consuming raw periwinkle preparations. The plant is not a safe herbal remedy — it is the source material for chemotherapy drugs. Traditional use for diabetes or hypertension should be redirected to safer alternatives.

Patient counselling script: "I need to be direct with you about periwinkle. The plant contains the same chemicals used in chemotherapy — very powerful drugs that suppress the immune system and can damage nerves. The pharmaceutical versions are carefully dosed in a hospital. Drinking periwinkle tea gives you an unpredictable dose of a chemotherapy drug. Please don't use it. There are safer herbs for diabetes and blood pressure."

2.9 Jack-in-the-Bush (Eupatorium odoratum)

Traditional use: Used across the Caribbean for colds, fever, wound healing, and as an insect repellent. Leaves applied topically to stop bleeding from cuts.

Interaction status: No clinically significant drug interactions have been confirmed in the available literature. The herb has demonstrated mild antimicrobial and anti-inflammatory activity in preclinical studies, but interaction evidence remains limited.

Clinical management: No interaction-specific intervention is indicated based on current evidence. Record use in the medication history, and reassess if symptoms emerge or if the medication regimen changes.

2.10 John Charles (Hyptis verticillata)

Traditional use: Used in Jamaica for colds, fever, headaches, and stomach complaints. Taken as tea.

Interaction status: No clinically significant drug interactions have been confirmed in available literature. Pharmacological and interaction data remain limited.

Clinical management: No interaction-specific intervention is indicated based on current evidence. Record use in the medication history, and reassess if symptoms emerge or if the medication regimen changes.

2.11 Medina (Alysicarpus vaginalis)

Traditional use: Used in Jamaica for colds, fever, and as a general tonic. Also used for urinary complaints.

Drug interactions:

Clinical risk: Low. The interactions are based on ethnobotanical reports and limited preclinical data. Clinically significant effects are unlikely at normal consumption levels but should be noted in patients on multiple antihypertensives or antidiabetics.

Clinical management: No interaction-specific intervention is indicated based on current evidence. Record use in the medication history, and reassess if symptoms emerge or if the medication regimen changes.

Section 3: Ten International Herbal Supplements

Caribbean patients also use internationally marketed herbal supplements — purchased from health food shops, pharmacies, or brought back from travels. These ten are the most commonly encountered in Caribbean practice and carry the most clinically significant interactions.

3.1 St. John's Wort (Hypericum perforatum)

The most dangerous herbal supplement in common use. St. John's Wort is a potent inducer of CYP3A4 and P-glycoprotein — two of the most important drug-metabolising systems in the body. It accelerates the clearance of dozens of medications, reducing their plasma levels below therapeutic thresholds.

Caribbean Practice Note: St. John's Wort is available over the counter in Caribbean pharmacies and health food shops. Patients may take it for mild depression without informing their clinician. The interaction with oral contraceptives is particularly relevant in the Caribbean, where unintended pregnancy carries significant social and economic consequences. The interaction with antiretrovirals is critical given the Caribbean's HIV prevalence.

3.2 Ginkgo Biloba

3.3 Garlic (Allium sativum — supplement dose)

Note: Dietary garlic at culinary doses is not clinically significant. The interaction applies to concentrated garlic supplements.

3.4 Ginger (Zingiber officinale — supplement dose)

Note: Same as garlic — culinary ginger is not clinically significant. Supplement doses are.

3.5 Turmeric / Curcumin (Curcuma longa)

3.6 Goji Berry (Lycium barbarum)

Caribbean Practice Note: Goji berries are consumed in Caribbean Chinese communities and increasingly as a mainstream "superfood." Patients on warfarin should be specifically warned.

3.7 Danshen (Salvia miltiorrhiza)

3.8 Dong Quai (Angelica sinensis)

3.9 Kava Kava (Piper methysticum)

3.10 Cranberry Juice

Caribbean Practice Note: Cranberry juice is widely consumed in the Caribbean. Most patients and clinicians do not consider it a drug interaction risk. Patients on warfarin should be advised to limit cranberry juice consumption or to have their INR checked more frequently if they drink it regularly.

Section 4: How to Ask the Right Question

The standard medication history question fails for herbal products. Here is a practical framework for Caribbean clinicians.

4.1 Why "Are you taking anything else?" doesn't work

Patients do not categorise bush teas, supplements, and traditional remedies as "medications" or "things they are taking." The question needs to be specific, normalising, and non-judgemental.

4.2 The three questions that work

Question 1: "Do you drink any bush teas — cerasee, fever grass, soursop leaf, guinea hen weed, anything like that?"

This question works because it names specific teas the patient will recognise, normalises the practice (implying it is common), and does not use the word "medication."

Question 2: "Do you take any supplements or natural remedies — vitamins, garlic capsules, turmeric, anything from the health food shop?"

This catches the international supplements that patients may not consider "herbal medicine."

Question 3: "Did anyone give you anything for your condition — a neighbour, family member, someone at the market?"

This catches the informal sharing of herbal remedies that is common in Caribbean communities.

4.3 What to do with the answer

Do not default to abrupt discontinuation. Unless the interaction is contraindicated, life-threatening, or clinically unstable (for example periwinkle, Aristolochia, kava kava with hepatotoxic agents), the clinician should:

1. Acknowledge the traditional use without dismissing it
2. Explain the specific interaction in plain language
3. Adjust the clinical plan (dose reduction, increased monitoring, or time-limited cessation when risk is high) while preserving a respectful, culturally informed discussion
4. Document the herbal use in the medication history so it is visible at future encounters

This approach maintains trust, produces better medication histories, and results in safer prescribing.

Section 5: About ElesRx

When a clinician enters a medication list that includes herbal products, ElesRx flags every interaction — herb-to-drug and herb-to-class — with the same severity grading, mechanism detail, and management guidance as conventional drug interactions. The ElesRx database contains validated interactions for all twenty-one herbs covered in this report.

The challenge is getting the herbs onto the list. ElesRx makes the analysis automatic. This report makes the asking easier.

elesrx.com — free tier available. Full access $9.99/month.

ElesRx is a product of PIPPS Smart Apps, a division of J.C. Epiphany Limited (Jamaica, est. 1998).

Section 6: Methodology and References

6.1 Data sources

Herbal interaction data is drawn from the ElesRx clinical database and verified against PubMed, PMC, DailyMed, LiverTox, the European Medicines Agency, and published systematic reviews. The source hierarchy and licensing constraints are the same as Reports 1 and 2.

Ethnobotanical data for Caribbean herbs is drawn from published surveys of traditional medicinal plant use in Jamaica, Trinidad and Tobago, and the OECS, cited individually below.

6.2 Limitations

The evidence base for herbal drug interactions is weaker than for conventional drug-drug interactions. Many interactions are documented at the preclinical level (in vitro or animal studies) rather than through clinical pharmacokinetic studies. Where the evidence level is preclinical only, this is noted in the monograph.

The concentration of active compounds in herbal preparations varies by plant source, preparation method, and storage conditions. This means that the dose-response relationship for herbal interactions is inherently less predictable than for pharmaceutical drugs.

This report covers twenty-one herbs. The ElesRx database contains interactions for additional herbal products not profiled here. The twenty-one were selected for their prevalence in Caribbean use and the clinical significance of their documented interactions.

6.3 Author and conflict of interest disclosure

This report was authored by Juliet Duncan, BPharm, founder of J.C. Epiphany Limited and developer of ElesRx. The author has a commercial interest in ElesRx. This report is published freely as a contribution to Caribbean clinical education. No external funding was received.

6.4 Citation

Duncan J. The Bush Medicine Blind Spot: When Caribbean Herbal Remedies Collide with Prescription Drugs. ElesRx Clinical Reports, Report 3. Published 2026 at elesrx.com/reports/bush-medicine-blind-spot/. J.C. Epiphany Limited, Jamaica.

References

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2. Conceição BCD, et al. Petiveria alliacea: a systematic review of its phytochemistry, pharmacology, and toxicology. Molecules. 2023;28(3):1398. doi:10.3390/molecules28031398

3. Joseph B, Jini D. Antidiabetic effects of Momordica charantia (bitter melon) and its medicinal potency. Asian Pac J Trop Dis. 2013;3(2):93–102. doi:10.1016/S2222-1808(13)60052-3

4. Moghadamtousi SZ, et al. Annona muricata (Annonaceae): a review of its traditional uses, isolated acetogenins and biological activities. Int J Mol Sci. 2015;16(7):15625–15658. doi:10.3390/ijms160715625

5. Izzo AA, Ernst E. Interactions between herbal medicines and prescribed drugs: an updated systematic review. Drugs. 2009;69(13):1777–1798. doi:10.2165/11317010-000000000-00000

6. MHRA Drug Safety Update. Cranberry juice and warfarin interaction. MHRA. 2004.