Igho Onakpoya

Dr. Igho Onakpoya

University of Oxford, Oxford, Oxfordshire, UK
orcid

Research Focus & Metrics

Academic Career Length

17Years (2010-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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4 February 2016 in BMC Medicine
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Journal Article
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IOIgho Onakpoya
Igho Onakpoya
CHCarl J. Heneghan
Carl J. Heneghan
JAJeffrey K. Aronson
Jeffrey K. Aronson
There have been no studies of the patterns of post-marketing withdrawals of medicinal products to which adverse reactions have been attributed. We identified medicinal products that were withdrawn because of adverse drug reactions, examined the evidence to support such withdrawals, and explored the pattern of withdrawals across countries. We searched PubMed, Google Scholar, the WHO’s database of drugs, the websites of drug regulatory authorities, and textbooks. We included medicinal products withdrawn between 1950 and 2014 and assessed the levels of evidence used in making withdrawal decisions using the criteria of the Oxford Centre for Evidence Based Medicine. We identified 462 medicinal products that were withdrawn from the market between 1953 and 2013, the most common reason being hepatotoxicity. The supporting evidence in 72 % of cases consisted of anecdotal reports. Only 43 (9.34 %) drugs were withdrawn worldwide and 179 (39 %) were withdrawn in one country only. Withdrawal was significantly less likely in Africa than in other continents (Europe, the Americas, Asia, and Australasia and Oceania). The median interval between the first reported adverse reaction and the year of first withdrawal was 6 years (IQR, 1–15) and the interval did not consistently shorten over time. There are discrepancies in the patterns of withdrawal of medicinal products from the market when adverse reactions are suspected, and withdrawals are inconsistent across countries. Greater co-ordination among drug regulatory authorities and increased transparency in reporting suspected adverse drug reactions would help improve current decision-making processes.

1 August 2014 in Nutrition, Metabolism and Cardiovascular Diseases
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IOIgho Onakpoya
Igho Onakpoya
ESElizabeth A. Spencer
Elizabeth A. Spencer
CHC. Heneghan
C. Heneghan
MTM. Thompson
M. Thompson

29 November 2016 in BMC Medicine
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Journal Article
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IOIgho Onakpoya
Igho Onakpoya
CHCarl J. Heneghan
Carl J. Heneghan
JAJeffrey K. Aronson
Jeffrey K. Aronson
We identified anti-obesity medications withdrawn since 1950 because of adverse drug reactions after regulatory approval, and examined the evidence used to support such withdrawals, investigated the mechanisms of the adverse reactions, and explored the trends over time. We conducted searches in PubMed, the World Health Organization database of drugs, the websites of drug regulatory authorities, and selected full texts, and we hand searched references in retrieved documents. We included anti-obesity medications that were withdrawn between 1950 and December 2015 and assessed the levels of evidence used for making withdrawal decisions using the Oxford Centre for Evidence-Based Medicine criteria. We identified 25 anti-obesity medications withdrawn between 1964 and 2009; 23 of these were centrally acting, via monoamine neurotransmitters. Case reports were cited as evidence for withdrawal in 80% of instances. Psychiatric disturbances, cardiotoxicity (mainly attributable to re-uptake inhibitors), and drug abuse or dependence (mainly attributable to neurotransmitter releasing agents) together accounted for 83% of withdrawals. Deaths were reportedly associated with seven products (28%). In almost half of the cases, the withdrawals occurred within 2 years of the first report of an adverse reaction. Most of the drugs that affect monoamine neurotransmitters licensed for the treatment of obesity over the past 65 years have been withdrawn because of adverse reactions. The reasons for withdrawal raise concerns about the wisdom of using pharmacological agents that target monoamine neurotransmitters in managing obesity. Greater transparency in the assessment of harms from anti-obesity medications is therefore warranted.

21 January 2019 in BMJ Open
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IOIgho Onakpoya
Igho Onakpoya
ETElizabeth T Thomas
Elizabeth T Thomas
JLJoseph J Lee
Joseph J Lee
BGBen Goldacre
Ben Goldacre
CHCarl Heneghan
Carl Heneghan
Objective To assess the benefits and harms of pregabalin in the management of neuropathic pain. Design Rapid review and meta-analysis of phase III, randomised, placebo-controlled trials. Participants Adults aged 18 years and above with neuropathic pain defined according to the International Association for the Study of Pain criteria. Interventions Pregabalin or placebo. Primary and secondary outcome measures Our primary outcomes were pain (as measured using validated scales) and adverse events. Our secondary outcomes were sleep disturbance, quality of life, Patient Global Impression of Change, Clinician Global Impression scale, anxiety and depression scores, overall discontinuations and discontinuations because of adverse events. Results We included 28 trials comprising 6087 participants. The neuropathic pain conditions studied were diabetic peripheral neuropathy, postherpetic neuralgia, herpes zoster, sciatica (radicular pain), poststroke pain and spinal cord injury-related pain. Patients who took pregabalin reported significant reductions in pain (numerical rating scale (NRS)) compared with placebo (standardised mean difference (SMD) −0.49 (95% CI −0.66 to −0.32, p<0.00001), very low quality evidence). Pregabalin significantly reduced sleep interference scores (NRS) compared with placebo (SMD −0.38 (95% CI −0.50 to −0.26, p<0.00001), moderate quality evidence. Pregabalin significantly increased the risk of adverse events compared with placebo (RR 1.33 (95% CI 1.23 to 1.44, p<0.00001, low quality evidence)). The risks of experiencing weight gain, somnolence, dizziness, peripheral oedema, fatigue, visual disturbances, ataxia, non-peripheral oedema, vertigo and euphoria were significantly increased with pregabalin. Pregabalin was significantly more likely than placebo to lead to discontinuation of the drug because of adverse events (RR 1.91 (95% CI 1.54 to 2.37, p<0.00001), low quality evidence). Conclusion Pregabalin has beneficial effects on some symptoms of neuropathic pain. However, its use significantly increases the risk of a number of adverse events and discontinuation due to adverse events. The quality of the evidence from journal publications is low.

14 December 2010 in Journal of Obesity
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IOIgho Onakpoya
Igho Onakpoya
SHShao Kang Hung
Shao Kang Hung
RPRachel Perry
Rachel Perry
BWBarbara Wider
Barbara Wider
EEEdzard Ernst
Edzard Ernst
The aim of this systematic review is to examine the efficacy ofGarciniaextract, hydroxycitric acid (HCA) as a weight reduction agent, using data from randomised clinical trials (RCTs). Electronic and nonelectronic searches were conducted to identify relevant articles, with no restrictions in language or time. Two independent reviewers extracted the data and assessed the methodological quality of included studies. Twenty-three eligible trials were identified and twelve were included. Nine trials provided data suitable for statistical pooling. The meta-analysis revealed a small, statistically significant difference in weight loss favouring HCA over placebo (MD: −0.88 kg; 95% CI: −1.75, −0.00). Gastrointestinal adverse events were twice as common in the HCA group compared with placebo in one included study. It is concluded that the RCTs suggest thatGarciniaextracts/HCA can cause short-term weight loss. The magnitude of the effect is small, and the clinical relevance is uncertain. Future trials should be more rigorous and better reported.

27 June 2018 in BMJ Evidence-Based Medicine
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APAnnette Plüddemann
Annette Plüddemann
JAJeffrey K Aronson
Jeffrey K Aronson
IOIgho Onakpoya
Igho Onakpoya
CHCarl Heneghan
Carl Heneghan
KMKamal R Mahtani
Kamal R Mahtani