The Placebo Effect May Involve Modulating Drug Bioavailability

The total effect of a medication is the sum of its drug effect, placebo effect (meaning response of placebo), and their interaction. Current interpretation of clinical trials (the gold standard of evidence-based-medicine) assumes no interaction, and the mechanism(s) underlying such interaction have not been fully explored. One possibility is that the placebo effect may modulate drug bioavailability. Using caffeine as a model drug, we have recently shown that the placebo effect of caffeine ingestion prolongs caffeine half life. Due to the novelty of this finding and its important clinical practice and clinical research implications, it needs to be confirmed in another set of subjects and extended to additional drugs.

The results of the study are expected to further our understanding of the mechanism of action of a widely used medical intervention, i.e., placebo. The results will be important for both clinical practice and clinical research.

Study Overview

• Status: Completed
• Conditions: Pharmacokinetics; Placebo Effect; Drug Half Life
• Intervention / Treatment: Drug: Caffeine, paracetamol, cephalexin, or ibuprofen; Drug: Placebo (caffeine, paracetamol, cephalexin, or ibuprofen)

Detailed Description

The total effect of a medication is the sum of its drug effect, placebo effect (meaning response of placebo), and their interaction. Current interpretation of clinical trials (the gold standard of evidence-based-medicine) assumes no interaction, and the mechanism(s) underlying such interaction have not been fully explored. One possibility is that the placebo effect may modulate drug bioavailability. Using caffeine as a model drug, we have recently shown that the placebo effect of caffeine ingestion prolongs caffeine half life. Due to the novelty of this finding and its important clinical practice and clinical research implications, it needs to be confirmed in another set of subjects and extended to additional drugs.

DESIGN: Balanced cross-over, single-dose, two-period, two-group deign comparing caffeine, paracetamol, cephalexin, and ibuprofen described as such (overt) to the same medication described as placebo (covert).

METHODS: 32, 50, 50, and 30 healthy adult volunteers will be enrolled in the caffeine (300 mg), paracetamol (500 mg), cephalexin (500 mg), and ibuprofen (400 mg) cross-over studies, respectively. Volunteers will be partially deceived to the intervention assignment (i.e., in the covert arm). Serum levels of each drug will be blindly determined by locally validated HPLC assays. Plasma half life (primary outcome) as well as Cmax, Tmax, and AUC (secondary outcomes) of each drug will be determined and analyzed by ANOVA.

• Study Type: Interventional
• Enrollment (Actual): 162
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Saudi Arabia
  • Riyadh, Saudi Arabia, 11211
    • King Faisal Specialist Hospital & Research Center

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 16 years to 58 years (Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

Description

Inclusion Criteria:

• Having no evidence of clinically important deviation from normal health as indicated by medical history, vital signs, and clinical laboratory tests.
• Acceptance to abstain from taking any medication other than birth control pills (including over-the-counter drugs) for at least 1 week prior to, and during the study; and from smoking and taking alcohol or caffeine or related xanthenes-containing beverages or food for 48 hours before and throughout each study period.
• Having good peripheral venous access.
• For the caffeine study, habitual daily caffeine intake should be 100-300 mg.

Exclusion Criteria:

• Women should be non-pregnant and non-lactating. For menstruating women, the study will be conducted 5 to 19 days after the last menstrual period and a urine pregnancy test will be performed.
• Should not have history of hypersensitivity to the drug to be tested or to its related compounds.
• Body Mass Index (BMI) should be less than 35 kg/m2.

Study Plan

How is the study designed?

Design Details

• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Triple

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: overt drug; The study has 4 sub-parts (one for each of 4 drugs), each sub-part has a crossover design. In this arm, the volunteer will be given one oral dose of 300 mg caffeine, 500 mg paracetamol, 500 mg cephalexin, or 400 mg ibuprofen and will be told that they are receiving such medication.	Drug: Caffeine, paracetamol, cephalexin, or ibuprofen; The study has 4 sub-parts (one for each of 4 drugs), each sub-part has a crossover design. In this arm, the volunteer will be given one oral dose of 300 mg caffeine, 500 mg paracetamol, 500 mg cephalexin, or 400 mg ibuprofen and will be told that they are receiving the active drug.
Placebo Comparator: Placebo (Covert drug); The study has 4 sub-parts (one for each of 4 drugs), each sub-part has a crossover design. In this arm, the volunteer will be given one oral dose of 300 mg caffeine, 500 mg paracetamol, 500 mg cephalexin, or 400 mg ibuprofen and will be told that they are receiving a placebo.	Drug: Placebo (caffeine, paracetamol, cephalexin, or ibuprofen); The study has 4 sub-parts (one for each of 4 drugs), each sub-part has a crossover design. In this arm, the volunteer will be given one oral dose of 300 mg caffeine, 500 mg paracetamol, 500 mg cephalexin, or 400 mg ibuprofen and will be told that they are receiving a placebo.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Plasma half life	The study has 4 sub-parts (one for eah of 4 drugs), each sub-part has a crossover design. The time frame to measure the outcome depends on the drug studied. For caffeine it is 24 hours, for paracetamol, it is 14 hours, for cephalexin, it is 6 hours, and for ibuprofen, it is 10 hours.	24 hours

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Area under the curve	The study has 4 sub-parts (one for eah of 4 drugs), each sub-part has a crossover design. The time frame to measure the outcome depends on the drug studied. For caffeine it is 24 hours, for paracetamol, it is 14 hours, for cephalexin, it is 6 hours, and for ibuprofen, it is 10 hours.	24 hours
Tmax	The study has 4 sub-parts (one for eah of 4 drugs), each sub-part has a crossover design. The time frame to measure the outcome depends on the drug studied. For caffeine it is 24 hours, for paracetamol, it is 14 hours, for cephalexin, it is 6 hours, and for ibuprofen, it is 10 hours.	24 hours
Cmax	The study has 4 sub-parts (one for eah of 4 drugs), each sub-part has a crossover design. The time frame to measure the outcome depends on the drug studied. For caffeine it is 24 hours, for paracetamol, it is 14 hours, for cephalexin, it is 6 hours, and for ibuprofen, it is 10 hours.	24 hours

Collaborators and Investigators

• Sponsor: King Faisal Specialist Hospital & Research Center

Publications and helpful links

General Publications

• Hammami MM, Yusuf A, Shire FS, Hussein R, Al-Swayeh R. Does the placebo effect modulate drug bioavailability? Randomized cross-over studies of three drugs. J Negat Results Biomed. 2017 May 23;16(1):10. doi: 10.1186/s12952-017-0075-2.

Study record dates

Study Major Dates

• Study Start: February 1, 2012
• Primary Completion (Actual): February 1, 2013
• Study Completion (Actual): February 1, 2013

Study Registration Dates

• First Submitted: December 26, 2011
• First Submitted That Met QC Criteria: December 28, 2011
• First Posted (Estimate): December 29, 2011

Study Record Updates

• Last Update Posted (Estimate): April 9, 2013
• Last Update Submitted That Met QC Criteria: April 8, 2013
• Last Verified: April 1, 2013

More Information

Terms related to this study

• Keywords: pharmacokinetics; Placebo effect; drug half life
• Additional Relevant MeSH Terms: Physiological Effects of Drugs; Neurotransmitter Agents; Molecular Mechanisms of Pharmacological Action; Anti-Infective Agents; Peripheral Nervous System Agents; Enzyme Inhibitors; Analgesics; Sensory System Agents; Anti-Inflammatory Agents, Non-Steroidal; Analgesics, Non-Narcotic; Anti-Inflammatory Agents; Antirheumatic Agents; Cyclooxygenase Inhibitors; Antipyretics; Purinergic Antagonists; Purinergic Agents; Anti-Bacterial Agents; Phosphodiesterase Inhibitors; Purinergic P1 Receptor Antagonists; Central Nervous System Stimulants; Acetaminophen; Ibuprofen; Cephalexin; Caffeine
• Other Study ID Numbers: RAC2101105